WO2009120664A2 - Test strip dispenser and interrogation device for optical monitoring of oil - Google Patents

Abstract

Herein are disclosed are systems for optical monitoring of oil quality. The systems comprise a dispensing device and a cradle adapted to receive the dispensing device. The dispensing device contains a supply of test strips and comprises a mechanism for extending a test strip out of the dispensing device so that it can be contacted with an oil sample. The systems further comprise an interrogation module for optically interrogating at least one test zone of the test strip, so as to monitor at least one parameter of the oil sample. In one embodiment, the monitored parameter is the free fatty acid content of the oil, and the optical interrogation is performed by an optical reflectance method.

Description

TEST STRIP DISPENSER AND INTERROGATION DEVICE FOR OPTICAL MONITORING OF OIL

Background

When oils (e.g. cooking oil, oil, fat, shortening, etc.) are exposed to high temperatures, particularly in the presence of oxygen and/or water, oxidative reactions can take place that result in degradation of the oils. Thus, oil quality is often monitored in restaurant kitchens, so as to determine whether the oil is still suitable for use.

A parameter often used to evaluate oil quality is the free fatty acid content of the oil. Mlinar and Neumayer, for example, disclose in US Patent 4,654,309 an article for testing liquid for free fatty acid content. An organic liquid to be tested is contacted with the article and any color change in the article after the passage of sufficient time is observed.

Summary

Herein are disclosed systems, methods and devices for evaluating the quality of oils (e.g., cooking oil or frying oil). The systems, methods and devices disclosed herein utilize a test strip, a strip-dispensing device, a cradle which is adapted to receive the dispensing device, and an optical interrogation module (which may be located either on the cradle or on the dispensing device). The dispensing device comprises a supply of test strips, and can extend a test strip so as to expose the test strip for contacting with an oil sample. In one embodiment, the test strips are contained in a replaceable cartridge which resides in a cavity in the dispensing device. Each test strip has at least one test zone whose optical properties are responsive to the free fatty acid content of the oil. In one embodiment, multiple test zones are provided, and the optical module comprises means to interrogate the multiple test zones and receive signals therefrom. A signal processing system is provided that can process the received signals and correlate the received signals with the free fatty acid content of the oil. A reporting system can be provided that can provide (to a user) an indication of the oil quality, based on the received, processed signals. The indication can be an actual numerical value of the concentration of free fatty acid; or, it can be a parameter that, while not directly equal to the actual numerical value, is associated with the value and can serve to allow the user to ascertain the quality of the oil (e.g., determine whether the oil is still suitable for use).

The systems, methods and devices disclosed herein are advantageous in using an optical interrogation module and a signal processing system to provide an indication of oil quality based on quantitative measurements of optical data, which may provide an improvement over methods that rely on subjective measurements (e.g. visual inspection). The strip-dispensing device can extend a test strip so as to expose test zones to be contacted with an oil sample, with the test strip being securely held by a mechanism within the strip-dispensing device. The secure holding of the test strip by the holding mechanism of the dispensing device enables the test zones of the test strip to be easily and accurately aligned with the components of the optical interrogation module for interrogation. Thus, the systems disclosed herein offer advantages over methods that require test strips to be manually handled (e.g., removed from a storage container by the fingers of a user), and/or methods that require manual placement of the test strip in optical alignment with an optical reader.

Thus in one aspect, herein is disclosed a device for dispensing a test strip and for optically interrogating the test strip, the device comprising a housing containing at least one test strip, wherein the test strip comprises a plurality of test zones each comprising an optical property that is responsive to the free fatty acid content of an oil sample; a mechanism for extending a portion of the test strip out of the device housing such that the plurality of test zones are exposed; an optical interrogation module for optically interrogating each of the test zones by a first optical mechanism and receiving signals therefrom; and, a system for processing the received signals and correlating the received signals with the free fatty acid content of the oil sample.

Thus in another aspect, herein is disclosed a system for dispensing a test strip and for optically interrogating the test strip, the system comprising a dispensing device containing at least one test strip, wherein the test strip comprises a plurality of test zones each comprising an optical property that is responsive to the free fatty acid content of an oil sample; a mechanism for extending a portion of the test strip out of the dispensing device such that the plurality of test zones are exposed; and, a cradle adapted for receiving the dispensing device, wherein the cradle comprises an optical interrogation module for optically interrogating each of the test zones by a first optical mechanism and receiving signals therefrom, and, a system for processing the received signals and correlating the received signals with the free fatty acid content of the oil sample.

Thus in yet another aspect, herein is disclosed a method of evaluating the quality of oil, the method comprising providing oil that potentially comprises free fatty acid content; providing a dispensing device containing at least one test strip, and a cradle adapted to receive the dispensing device, wherein the test strip contains a plurality of test zones, wherein each test zone is responsive to free fatty acid; extending a portion of the test strip out of the dispensing device such that the plurality of test zones are exposed, contacting the oil with the test strip such that the oil is brought into contact with at least a portion of each of the test zones; aligning the plurality of test zones with an optical interrogation module comprising light sources and photodetectors; interrogating the plurality of test zones so as to receive signals therefrom; processing the received signals; correlating the received signals with the free fatty acid content of the oil; and, reporting an indication of the oil quality of the oil, wherein the indication is associated with the free fatty acid content of the oil.

Drawings

Fig. Ia is a top plan view of an exemplary test strip. Fig. Ib is a side cross sectional view of an exemplary test strip.

Fig. 2 is an exploded perspective view of an exemplary cradle, dispensing device, and cartridge.

Fig. 3 is a perspective view of an exemplary dispensing device, optical module, and test strip, with the test strip in an extended position. Fig. 3a is a magnified perspective view of the portion of Fig. 3 indicated by oval

3a, and shows an exemplary optical module and test strip.

Fig. 4 is an exploded perspective view of an exemplary cradle, dispensing device, and cartridge.

Fig. 5 is a perspective view of an exemplary dispensing device, cradle, optical module, and test strip, with the test strip in an extended position.

Fig. 5a is a magnified perspective view of the portion of Fig. 5 indicated by oval 5a, and shows an exemplary optical module and test strip. Fig. 6 is a cross section view of an exemplary cartridge containing test strips.

Fig. 7 is a plan view of portion of an exemplary optical interrogation module.

Fig. 8 is a side cross sectional view of an exemplary arrangement of a light source, a photodetector and test strip. Fig. 9 is a block diagram of one embodiment of an oil quality monitoring system.

Fig. 10 is a plot of optical reflectance of test strips comprising oil samples of various free fatty acid concentrations.

Fig. 11 is a plot of optical reflectance of test strips comprising oil samples of various free fatty acid concentrations. Fig. 12 is a plot of optical reflectance of test strips comprising oil samples of various free fatty acid concentrations.

Fig. 13 is a plot of optical reflectance of test strips comprising oil samples of various free fatty acid concentrations.

Fig. 14 is a plot of photodetector response to reflected light from test strips under various conditions.

Fig. 15 is a plot of fluorescence of test strips comprising oil samples of various total polar compound concentrations.

Drawings and elements therein are not to scale unless noted. In the Figures, like reference numerals are used to designate like features throughout. Although terms such as

"top", bottom", "upper", lower", "over", "under", "front", "back", and "first" and "second" may be used in this disclosure, it should be understood that those terms are used in their relative sense only.

Detailed Description

Disclosed herein are systems and methods for evaluating the quality of oil (e.g. frying oil, vegetable oil, shortening, tallow, grease, etc). The systems and methods rely on a sampling substrate (i.e., a test strip 1, that can be disposed after use), a strip-dispensing device 50, and a cradle 60. Cradle 60 is adapted to receive dispensing device 50 and to recharge dispensing device 50 while device 50 is received onto cradle 60. Dispensing device 50 contains at least one test strip 1 located within housing 59 of dispensing device 50, and comprises a mechanism for extending test strip 1 partially out of housing 59 of dispensing device 50 so that an oil sample can be contacted with at least a portion of test strip 1. The system also comprises an optical module (device) 30 for interrogation of test zones 10 of test strip 1.

With reference to Figs. Ia and Ib, test strip 1 is comprised of a porous, oil- absorbent material 5. In this context, the term oil-absorbent means that the material is capable of absorbing oil into the porous interior of the material (e.g., capable of being wetted and/or penetrated by the oil). In various embodiments, material 5 comprises paper, nonwoven, open-celled foam, woven fabric, and the like.

Test strip 1 comprises at least one test zone 10 whose optical properties are responsive to the free fatty acid content of an oil sample. In one embodiment, multiple test zones 10a, 10b, etc. are provided, as shown in the exemplary configuration of Figs. Ia and Ib. In one embodiment, the optical property is a reflectance property, as explained in further detail herein.

In one embodiment, the optical properties of test zone 10 are responsive to the presence of free fatty acid in the oil by virtue of the presence of an acid-base indicator in test zone 10. The indicator may comprise any molecule, or combinations of molecules, that is capable of providing a color change (and hence is capable of displaying an altered optical reflectance at one or more wavelengths) in response to a change in pH. Suitable indicators include for example m-cresol purple, neutral red, thymol blue, phenol red and cresol red.

In one embodiment, test zone 10 also comprises a base compound, which may be any organic or inorganic base compound, including for example sodium carbonate, sodium bicarbonate, and so on. The amount of base compound in each test zone 10 may vary and may be selected in an amount that allows the particular test zone to be responsive to a given amount of acid. Thus in the exemplary configuration of Figs. Ia and Ib, different amounts of base can be provided in different test zones 10a, 10b, 10c and 1Od. In such an arrangement test zone 10a, for example, may be responsive to a different amount of free fatty acid than is test zone 10b (or, alternatively phrased, zones 10a and 10b may respond differently to the same amount of free fatty acid), and so on. In such manner, a test strip 1 can be provided that is responsive to a wide range of free fatty acid concentrations. In various embodiments, at least two, three, four, or five test zones 10 may be used. In various embodiments, zones may be used that are responsive to oil with a content of approximately, e.g., 0.1% - 0.5% free fatty acid, 0.5% - 1.0% free fatty acid, 1.0% - 1.5% free fatty acid, 1.5% - 2.0% free fatty acid, 2.0% - 2.5% free fatty acid, 2.5% - 3.5% free fatty acid, 3.5% - 5.0% free fatty acid, or 5.0% - 7.0% free fatty acid. If desired, one or more additional test zones may be provided that comprise a similar (or the same) amount of base as does another test zone (i.e., that respond similarly to the same amount of free fatty acid).

In one embodiment, test zone 10 also comprises a nonvolatile, pH-neutral humectant that is capable of solubilizing the acid-base indicator and the base compound. Suitable humectants, for example, include dihydroxy aliphatic polyethylene glycol compounds such as those available from Dow Chemical under the designation Carbowax

200, Carbowax 400, and Carbowax 600, and Carbowax 1500.

In one embodiment, the at least one test zone 10 is formed on test strip 1 by mixing the humectant, base compound, and the acid-base indicator (and optionally, volatile solvent such as water or organic solvent) to provide an impregnant mixture, impregnating selected regions of test strip 1 with the impregnant mixture (e.g. by coating, dipping, etc.) such that the impregnant mixture penetrates into (impregnates) the interior of porous material 5 of test strip 1, and allowing test strip 1 to dry (if necessary).

Multiple test zones 10 may be used, and may comprise discrete zones (i.e. they may be physically separated by areas 20 that are not test zones 10). For example, if multiple zones are used (e.g., that differ in their concentration of base compound), it may be useful to minimize the chance of the respective impregnant mixtures migrating (e.g., by wicking laterally through the porous material 5 of test strip 1) so as to encounter each other. Thus in one embodiment, impregnant mixtures are deposited sufficiently far apart to leave areas 20 (which do not contain impregnated materials) therebetween. In a further embodiment, at least a portion 21 of selected area or areas 20 of test strip 1 can be treated (prior to impregnating test strip 1 with impregnant mixture) so as to minimize or prevent migration of the impregnant mixture. Such barrier treatments can be applied to the surface of test strip 1 and/or to the interior of test strip 1 (i.e., to the interstitial surfaces of porous material 5 that comprises test strip 1), and may include, for example, plasma treatment, vapor deposition, and the like, in a manner that serves to decrease the surface energy (i.e. wettability) of the porous material 5. In a specific embodiment, the barrier treatment comprises depositing (e.g., coating) a barrier material precursor onto one or both major surfaces of test strip 1 and retaining the deposited barrier material thereon. In one embodiment, the barrier material precursor penetrates into the porous interior spaces of the test strip material 5 and coats the interior surfaces thereof. In various embodiments, suitable barrier materials include those materials that (when deposited and solidified) comprise a very low surface energy, e.g. less than 30 dynes/cm, less than 25 dynes/cm, or less than 20 dynes/cm. Suitable materials include silicones, fluorosilicones, and the like.

Such a low surface energy barrier treatment can be provided in certain locations 21 (for example, bordering one or more test zones 10, as in the exemplary arrangement shown in Figs. Ia and Ib). Such a barrier treatment may serve to minimize the chance of an impregnant mixture migrating out of its desired location during and after the impregnation process. It may also serve to minimize the chance, during testing, of an oil sample migrating from a test zone (e.g. 10a) to a nearby test zone (e.g. 10b), which might compromise the test results .

Thus in one embodiment, methods disclosed herein comprise treating at least one area of a test strip to form a barrier area 21, leaving at least one untreated area on the test strip. An impregnant solution can then be deposited on at least a portion of the untreated area(s), so as to form at least one test zone 10. In one embodiment, at least two areas of the test strip are treated to form barrier areas 21, leaving an untreated area therebetween. An impregnant solution can then be deposited on at least a portion of the untreated area in between the barrier areas 21, so as to form at least one test zone 10. In one embodiment, after the above processes are performed, at least one area remains which is neither treated with a barrier treatment nor impregnated with an impregnant solution. Methods of making test strips 1 (e.g., with test areas comprising an acid/base indicator, a base compound and a humectant), are described in further detail by Mlinar and Neumayer in US Patent 4,654,309.

Test strips 1 can be produced in a variety of configurations. For example, while one convenient configuration of test strip 1 is a rectangular strip (and while the term test strip is used generally herein with reference to the sampling substrate), it is understood that the test strip can be in any convenient shape or configuration, such as square, circular, etc. In one embodiment, test strip 1 is symmetrical with regard to the front and back major surfaces of test strip 1. In such a case, an oil sample can be contacted with either or both major surfaces of test strip 1, and/or test strip 1 may be placed with either of the major surfaces of test strip 1 facing optical interrogation module 30, for optical interrogation of test zones 10. In one embodiment, test strip 1 comprises a leading end 11 and a trailing end 12, with test zones 10 being positioned relatively closer to leading end 11 than to trailing end 12 (e.g., as shown in the exemplary embodiment of Figs. Ia and Ib).

Test strips 1 can also contain reference zones as discussed later herein, and can also contain one or more marks (i.e., features, as achieved, for example, by printing or laser-marking). Such marks may be visually detectable by a user, and/or may be detectable by an interrogation device (for example, by optical module 30). Such marks may, for example, be used by the user or by the system to confirm that a particular test strip 1 is compatible with the system; e.g., to confirm that a particular test strip 1 was designed and/or manufactured in accordance with specifications, tolerances, etc., that enable test strip 1 to be satisfactorily used with dispensing device 50 and/or cradle 60. The methods disclosed herein involve contacting an oil sample with test strip 1 such that the oil sample comes into contact with at least a portion of some or all of test zones 10 (this may be done by dipping test strip 1 in the oil, by depositing the oil sample onto test strip 1, and so on). By virtue of the presence of the acid-base indicator, test zones 10 may display different optical absorbtive/reflective properties depending on the amount of free fatty acid in the oil sample. Such optical absorbtive/reflective properties include any measurable property relating to the fact that when a material receives incident light, some light may be absorbed, some may be remitted (e.g. reflected), and some may be transmitted. Any such observable property may be used (i.e. measured) in the methods and devices disclosed herein. In one embodiment, the particular measurement that is used is reflectance. In other embodiments, the particular measurement that is used is absorbtion or transmission.

Thus in summary a set of operations can be performed which involve contacting test strip 1 with an oil sample, and then optically interrogating at least one test zone 10. Thus, with reference to Figs. 2 and 4, the systems disclosed herein comprise a dispensing device 50 that can be used to contact test strip 1 with an oil sample and to place test strip 1 in position for optical interrogation. In one embodiment dispensing device 50 comprises a housing 59 that defines an interior volume. Housing 59 comprises a generally elongate main body 52 and further comprises a relatively narrowed portion to facilitate grasping by a users hand. Dispensing device 50 is configured to be received by cradle 60 and to rest securely on cradle 60, and can have one or more optional features (e.g., projection 51) that mate with a corresponding feature (e.g., slot 68) of cradle 60. In one embodiment dispensing device 50 comprises a rechargeable battery or batteries (not shown in any figure), which can be recharged by a charging mechanism (also not shown) located within cradle 60.

Dispensing device 50 is configured to contain at least one test strip 1. More specifically, dispensing device 50 is configured to store the at least one test strip 1 in a condition in which it is substantially contained within housing 59 of dispensing device 50 until such time as it is desired to use test strip 1. Dispensing device 50 contains a mechanism capable of exposing test strip 1 such that it can be contacted with an oil sample. In one embodiment, the exposing of test strip 1 comprises extending a portion of test strip 1 outside of housing 59 of dispensing device 50 (e.g., into an extended position, as shown in Figs. 3 and 5). In one embodiment, when in an extended position test strip 1 protrudes through slot 56 from terminal end 57 of dispensing device 50. (In a specific embodiment, test strip 1 and dispensing device 50 each comprise a long axis, and the long axis of test strip 1 is substantially aligned with the long axis of dispensing device 50, during storage of test strip 1 within dispensing device 50 and when test strip 1 is in an extended position.) When so extended, a portion of test strip 1 (e.g., the portion closest to trailing end 12, and typically not comprising any test zones 10) remains within housing 59 of dispensing device 50 and is securely held by a grasping mechanism such that the strip is not accidentally dislodged. Thus, when test strip 1 is in an extended position, a user can grasp dispensing device 50 and use it to bring test strip 1 into contact with an oil sample. This may be done by dipping test strip 1 into the oil; or, an oil sample can be deposited onto test strip 1.

In one embodiment, dispensing device 50 contains a multiplicity of test strips 1, arranged in a replaceable/disposable cartridge 70 which is adapted to be received into a cavity 53 in dispensing device 50 (e.g., as shown in Figs. 2 and 4). Cartridge 70 thus represents a convenient way to package a supply of test strips 1. With respect to Fig. 6, cartridge 70 comprises a housing 79 that at least partly defines a cavity configured to receive a stack of test strips 1. In one embodiment, cartridge 70 comprises a generally elongate housing that comprises major wall 71, first and second end walls 72 and 73, and side walls 74. Cartridge 70 further comprises first and second flanges 75 and 76 at opposing ends of the "open" side of cartridge 70 (e.g., that cover a portion of each end of the test strip stack), that define an opening 77 therebetween. Cartridge 70 can also comprise an at least partially detachable cover (not shown) that can cover opening 77. The cover can be removed partially, or completely, when it is desired to access and/or remove test strips 1 from cartridge 70. The cover may be reversibly detachable, such that it can be partially or completely detached to remove a test strip 1 , and then reattached until the next test strip is removed. Cartridge 70 can also include one or more biasing elements 80 that act to urge at least a portion of the test strip stack toward opening 77. Such an arrangement biases the test strip stack towards opening 77 so that when the topmost test strip 1 is removed from the stack, the next test strip in the stack is placed in a position ready for removal, and so on. In various embodiments, biasing element 80 can comprise a piece of resilient material such as a compressible foam (e.g. foam rubber), a piece of intrinsically resilient solid material (e.g. rubber, silicone, etc.), and the like. The resilient material can be backed by a solid material if desired. In an alternative embodiment (shown in Fig. 6), biasing element 80 comprises a platen (e.g. a piece of solid material) backed by a spring. In still another alternative embodiment, biasing element 80 comprises a leaf spring. Such a leaf spring can comprise a member made of stiff, resiliency flexible material, that is fixed at a proximal end (e.g., attached to a portion of major wall 71 of cartridge 70) and free at a distal end, with the distal end being positioned closer to opening 77 than is the proximal end.

Cartridge 70 may serve several useful purposes in addition to its use as a convenient way of supplying test strips 1 to dispensing device 50. For example, cartridge 70 may serve as a storage container for test strips 1 even if the test strips are not to be used with the systems disclosed herein (e.g., if the test strips are to be dipped by hand into an oil sample rather than used with device 50). In such case, rather than test strip 1 being removed from a package and manually grasped (thus encountering the risk of contamination by skin oils etc.), a test strip may be partially extended from cartridge 70 and the cartridge may be used as a handle by which to lower test strip 1 into the oil. Thus, cartridge 70 may serve to minimize the manual handling of test strips, may minimize the chance of accidentally removing multiple test strips and then replacing a contaminated test strip into the test strip container, and so on.

For use with the systems disclosed herein, cartridge 70 is configured to be insertable into cavity 53 of dispensing device 50, and to be easily removable from cavity 53 when cartridge 70 is empty. Accordingly, in one embodiment cartridge 70 comprises indented surfaces 81 suitable for being grasped by a user. Cartridge 70 can also comprise a cover portion 82 (e.g., a decorative cover) which may overlap at least a portion of the housing of dispensing device 50 when the cartridge is fully inserted into cavity 53.

In normal use, cartridge 70 is fully inserted into cavity 53 of dispensing device 50 with opening 77 facing the interior of device 50. Dispensing device 50 comprises a mechanism configured to remove the uppermost test strip 1 from cartridge 70 and a mechanism configured to extend a portion of strip 1 outside of the housing 59 of dispensing device 50. In a specific embodiment, a single mechanism is used to perform both the removing of test strip 1 from cartridge 70, and the extending of test strip 1 out of housing 59 of dispensing device 50. In one embodiment, cavity 53 is arranged such that cartridge 70 is aligned along the long axis of device 50, and the extending mechanism is configured to extend strip 1 out of a slot opening 56 at terminal end 57 of the housing 59 of dispensing device 50.

The removing mechanism can be any suitable mechanism capable of removing a strip from the cartridge, including for example a pushrod (sliding) actuator, one or more rotating spiked wheels, etc. Often, such mechanisms act to urge an item directly in the direction of desired travel. However, a certain mode of removal has been found by the inventors to be particularly advantageous in overcoming the high frictional characteristics typically exhibited by test strips 1. Thus, in one embodiment, dispensing device 50 comprises a mechanism comprising one or more picker arms. The picker arm can be actuated by any suitable mechanism (a cam, a driven belt, etc.) powered by an electric motor. The terminal end of the picker arm(s) can comprise any suitable end, for example a blunt end or a flared end, but in a specific embodiment it comprises a sharp tapered end. The picker arm is configured such that, upon actuation of the picker arm, the terminal end of the picker arm contacts the surface of the uppermost test strip at a particular location and causes this portion of test strip 1 to initially move in a direction retrograde to the desired direction of extension of the strip. Thus, with reference to Fig. 6, the picker arm may contact the upper most test strip at or near location 83 and urge this portion of test strip 1 to move in the direction noted as (-) in Fig. 6. Trailing end 12 of test strip 1 being blocked from moving very far, or at all, in this direction by second end wall 73 of cartridge 70 (or, by another suitable mechanism if desired), this local movement of a portion of test strip 1 will result in at least a portion of test strip 1 (typically, a portion between location 83 and trailing end 12) protruding through opening 77 and forming an arcuate shape. This results in motion of leading end 11 of test strip 1 in the (-) direction, to the point that leading end 11 is no longer in underlapping relation with first flange 75 of cartridge 70. Once this occurs, the resiliency of the test strip material, and/or the pressure exerted by resilient element(s) 80, will result in terminal end 11 of test strip 1 being released from the test strip stack (if desired, the picker arm can be actuated so as to further motivate this process). At this point, the picker arm can be removed from contact with test strip 1; or the direction of motion of the picker arm can be changed (e.g., reversed) so as to move test strip 1 in the (+) direction so as to pull trailing end 12 of test strip 1 free of second flange 76.

The result of this operation is that test strip 1 is free of cartridge 70 and is ready to be extended (in the (+) direction, with regard to Fig. 6) such that a portion of test strip 1 protrudes out of housing 59 of dispensing device 50. A suitable extension mechanism can be used to move test strip 1 (typically, in a direction along its long axis) to slot 56 in housing 59 and partially through slot 56 such that at least the test zones 10 of test strip 1 are exposed. Suitable extension mechanisms may include motorized rollers which are pressed together so as to pinch test strip 1 between them and urge test strip 1 in the desired direction; a pushing member attached to the end of an actuated push rod; and the like. The aforementioned picker arm could also be used if appropriately actuated in the desired manner. In one embodiment, dispensing device 50 is configured to be held with the long axis of device 50 in a substantially vertical position during the extending process, and gravity may assist in the extension of test strip 1.

Once test strip 1 is extended to a sufficient extent (e.g., as shown in Figs. 3 and 5) a mechanism is used (which may be the same as the extension mechanism, or a separate mechanism) to securely hold the remaining portion of test strip 1 (i.e. the portion remaining inside housing 59 of device 50), such that the strip does not become dislodged. In one embodiment, the portion of test strip 1 that is so held is the portion nearest trailing end 12; i.e., the portion that does not comprise test zones 10. The holding mechanism may include a feature that allows a user to release test strip 1 at a desired time (e.g., after test strip 1 has been interrogated) so that test strip 1 can be discarded.

When in an extended position, test strip 1 can be contacted with an oil sample. After contact with the oil sample, test strip 1 can be optically interrogated by directing light on the at least one test zone 10 and measuring the reflected light therefrom. Such optical interrogation can be performed by an optical interrogation module 30, of which an exemplary design is pictured in Figs. 3, 3a, 5, 5a, and 7. With reference to Fig. 7, optical module 30 comprises at least one light source 31 for directing light onto at least one test zone 10 of test strip 1. In one embodiment, optical module 30 comprises fewer light sources 31 than test strip 1 comprises test zones 10 (in a particular embodiment, one light source 31 is used). In such an embodiment, at least one light source 31 is used to direct light onto more than one test zone 10. This can be done by using a common light source to simultaneously direct light onto multiple test zones 10. Or, it can be done by directing light from one light source 31 sequentially onto multiple test zones 10, e.g. by moving light source 31 and test strip 10 relative to each other.

In an alternate embodiment, multiple light sources 31 are used to direct light onto multiple test zones 10. In a particular embodiment, the same number of light sources 31 and test zones 10 are used. For example, in the exemplary design shown in Figs. 1 and 7, optical module 30 comprises four light sources 3 Ia, 3 Ib, 3 Ic and 3 Id, and test strip 1 comprises four test zones 10a, 10b, 10c and 1Od. In one embodiment, light sources 31 are spatially arranged so as to correspond to the spatial arrangement of zones 10 (i.e., light sources 31 and test zones 10 are aligned such that light can be directed from each light source 31 onto each corresponding test zone 10 without having to move test strip 1 and optical module 30 relative to each other). For example, test zones 10 may be arranged in a linear format at a given center to center spacing, with light sources 31 arranged in the same format. Light sources 31 can be configured so as to all operate simultaneously or near-simultaneously; or, they be configured to operate in sequence.

Light source 31 may comprise any of a variety of light sources, including bulbs (e.g. incandescent bulbs) and the like. In one embodiment, light source 31 comprises a light-emitting diode (LED), which may be particularly advantageous in the present methods. In various embodiments, an LED can be used that emits light in a particular wavelength range (e.g. green, blue, red, IR, etc.). In a particular embodiment, a white LED is used (i.e., an LED that emits radiation of wavelengths covering at least a substantial portion of the visible spectrum). One exemplary LED that can be used is available from Super Bright LEDs, St. Louis, Missouri, under the designation RL5-W5020. In further configurations, different wavelength LEDs can be used as light sources to interrogate different test zones.

With reference to Fig. 8, optical module 30 also comprises at least one photodetector 32 for measuring reflected light from at least one test zone 10. In one embodiment, optical module 30 comprises fewer photodetectors 32 than test strip 1 comprises test zones 10 (in a particular embodiment, one photodetector 32 is used). In such an embodiment, interrogation of the test zones involves using one photodetector to measure light from more than one test zone 10. This can be done, for example, by sequentially measuring light from individual test zones 10.

In an alternate embodiment, multiple photodetectors 32 are arranged to receive light reflected from multiple test zones 10. In a particular embodiment, the same number of photodetectors 32 and test zones 10 are used. For example, in the exemplary design shown in Figs. 1 and 7, optical module 30 comprises four photodetectors 32a, 32b, 32c and 32d, and test strip 1 comprises four test zones 10a, 10b, 10c and 1Od. In one embodiment, photodetectors 32 are spatially arranged so as to correspond to the spatial arrangement of test zones 10 (e.g., such that light can be received by photodetectors 32 without having to move test strip 1 and optical module 30 relative to each other).

Photodetector 32 may comprise any of a variety of devices capable of measuring the number of incident photons, including for example a photomultiplier tube, a photovoltaic cell, a charge coupled device, and the like. That is, photodetector 32 serves to convert the signal received from test zone 10 (the intensity or strength of reflected light) to a signal (e.g., a voltage) that can be further processed by signal processing system 37 (as discussed in detail later herein). In one embodiment, photodetector 32 comprises a photodiode. In various embodiments photodetector 32 can be configured to detect light of a specific, relatively narrow wavelength range (for example, the green, blue, red or IR wavelength ranges mentioned above); or, photodetector 32 can be configured to detect light over relatively wide wavelengths. In a specific embodiment, photodetector 32 comprises a photodiode that is configured to detect light over a substantial portion of the visible spectrum, e.g. in the wavelength range of about 400 nm to about 800 nm. In a particular embodiment, the wavelength of light detectable by photodetector 32 is chosen so as to cover substantially the same range as the light emitted by light source 31. One exemplary photodetector that can be used is a photodiode available from Hamamatsu Photonics of Hamamatsu City, Japan, under the designation S9345.

In one embodiment, optical module 30 comprises at least one mated light source 31 and photodetector 32 pair that are configured so as to be able to optically interrogate at least one test zone 10 on test strip 1. Accordingly, light source 31 can be configured in optical module 30 so as to be able to be placed near to a test zone 10, such that at least a portion of the light output of source 31 can be directed toward test zone 10. With reference to Figs. 7 and 8, in one embodiment light source 31 is positioned behind cover 33 of optical module 30, with cover 33 comprising an optically transmissive portion 34 over source 31, such that light emitted from source 31 may be directed toward test zone 10.

Photodetector 32 can be configured in optical module 30 so as to be able to receive a reflected signal from test zone 10 upon the use of light source 31 to direct light onto test zone 10. For example, it may be useful to position photodetector 32 closely beside light source 31, as shown in the exemplary designs of Figs. 7 and 8. In various embodiments, photodetector 32 may be positioned at most about 5 mm, 10 mm, or 15 mm from light source 31. Additionally, it may be advantageous to mount light source 31 and photodetector 32 on a common printed circuit board 38, which may result in light source

31 and photodetector 32 being in a substantially coplanar configuration (as shown in Fig. 8). In such a case, photodetector 32 may also be placed behind cover 33 of optical module 30, with cover 33 comprising an optically transmissive portion 35 over photodetector 32, such that at least a portion of light reflected from test zone 10 may be detected by photodetector 32.

In various embodiments, light source 31, photodetector 32, and/or optically transmissive portions 34 and/or 35, may be configured so as to most efficiently direct light from source 31 onto test zone 10, and to collect reflected light therefrom by photodetector 32, while at the same time minimizing ambient light (or light from an adjacent light source) incident upon photodetector 32. Thus in an exemplary configuration in which photodetector 32 is positioned adjacent light source 31 and slightly off-axis relative to a direct path between light source 31 and test zone 10 (e.g., as shown in Fig. 8), optically transmissive portion 35 can be angled (as in Fig. 8), or can be made somewhat larger than the light-sensitive surface of photodetector 32 (e.g., as shown in Fig. 7), so as to not block any portion of the light that would otherwise reach photodetector 32. Similarly, optically transmissive portion 34 can be likewise configured, if desired. Optically transmissive portions 34 and/or 35 can be optically transparent across substantially all of the visible light spectrum. Or, one or both portions 34/35 can include optical filters so as to block light of unwanted wavelengths while permitting the passage of light of desired wavelengths. Such filters can, in addition to being wavelength dependent, can be angle dependent (for example, so as to block ambient light). Thus in summary, a light source/photodetector pair 31/32 may be configured such that upon the proper positioning of optical module 30 relative to test strip 1, at least a portion of light emitted from source 31 can impinge upon a test zone 10, and at least a portion of light reflected from test zone 10 can be detected by photodetector 32. All, or even a substantial portion, of the light emitted by light source 31 does not necessarily have to be directed onto test zone 10. Likewise, photodetector 32 does not have to capture all, or even a substantial portion, of the light reflected from test zone 10. All that is necessary is that sufficient light is directed from light source 31 onto test zone 10, and sufficient reflected light therefrom is measured by photodetector 32, with sufficiently little interference from ambient light, such that a signal can be generated by photodetector 32 and processed as described herein, to allow an accurate indication of the oil quality to be generated.

An optical module 30 as disclosed herein may allow accurate interrogation via optical reflectance, with minimum use of space and with minimum expense, since it minimizes the use of components such as fiber optic cables, lens arrays, filter wheels, and the like. That is, optical module 30 as disclosed herein may be much less expensive than devices such a spectrophotometers, optical densitometers, and the like.

In one embodiment (illustrated in Figs. 1 and 7), module 30 comprises mated pairs of light sources/ photodetectors 31a/32a, 31b/32b, etc., which mated pairs are spatially arranged such that they can be brought into proper alignment with test zones 10a, 10b, etc., respectively, so as to form a plurality of light source/photodetector/test zone sets, such that multiple test zones 10 of test strip 1 can be interrogated without needing to move test strip 1 and module 30 relative to each other. In various embodiments, optical module 30 may be located either on dispensing device 50 (as shown in Fig. 3), or on cradle 60 (as shown in Fig. 5).

In the embodiment in which module 30 is located on dispensing device 50, module 30 can be movable between a first, secured position, and a second, extended position in which optical interrogation of test zones 10 of test strip 1 can be performed. For example, with reference to Figs. 2 and 3, module 30 can be attached to an element 55 which is movable between a first, secured position (as shown in Fig. 2) and a second, extended position (as shown in Fig. 3). Thus, after test strip 1 is extended from slot 56 and contacted with an oil sample, element 55 (comprising optical module 30) can be moved (either by use of a motorized actuator, or manually by the user) to an extended position. The position of optical module 30, the position of light sources 31 and photodetectors 32 on optical module 30, the positioning of test strip 1 in its extended position, and the location of test zones 10 on test strip 1, are designed in combination so as to place test zones 10 of test strip 1 in alignment with light sources 31 and photodetectors 32 (as shown in Fig. 3 and in the magnified view of Fig. 3a) so that optical interrogation can be performed.

In one embodiment, test strip 1 is allowed to extend freely from terminal end 57 of dispensing device 50 for interrogation, without being contacted by any other portion of device 50. In an alternative configuration, dispensing device 50 comprises a holding mechanism (that may be mounted to extendable portion 55) that is configured to contact test strip 1 and hold it in position for optical interrogation. Such a mechanism might comprise for example a clamp to hold leading end 11 of test strip 1, or, a clamshell mechanism configured to envelop a significant portion of test strip 1 (in such a configuration, any portion of the clamshell device located between a test zone 10 and a light source 31 and/or photodetector 32 should be transparent). In an alternate embodiment in which optical module 30 is located on cradle 60, module 30 can be located on cradle 60 such that when dispensing device 50 (with oil- contacted test strip 1 extended therefrom), is received by cradle 60, test strip 1 is aligned with optical module 30 so that optical interrogation of test zones 10 can be performed. That is, the position of optical module 30 on cradle 60, the position of light sources 31 and photodetectors 32 on optical module 30, the positioning of test strip 1 in its extended position on dispensing device 50, and the location of test zones 10 on test strip 1, are designed in combination such that when dispensing device 50 (with oil-contacted test strip 1 extended therefrom) is received by cradle 60, test zones 10 of test strip 1 are aligned with light sources 31 and photodetectors 32 (as shown in Fig. 5 and in the magnified view of Fig. 5a) such that optical interrogation can be performed

Cradle 60 may comprise a shielding portion 65 that can help to shield test zones 10 and/or optical module 50 from ambient light. One exemplary shielding portion 65 is shown in Fig. 5. In one embodiment, the shield portion is movable or removable to allow optical module 30 to be accessed for cleaning.

In one embodiment, test strip 1 is allowed to extend from dispensing device 50 for interrogation, without being contacted by any portion of cradle 60. In an alternative configuration, cradle 60 comprises a holding and aligning mechanism that is configured to contact test strip 1 and hold it in position for optical interrogation. Such a mechanism might comprise, for example, a clamp to hold the leading end 11 of test strip 1, or, a clamshell mechanism configured to envelop a significant portion of test strip 1 (in such a configuration, any portion of the clamshell device located between a test zone 10 and a light source 31 and/or photodetector 32 should be transparent).

Cradle 60 is adapted to receive dispensing device 50 and can comprise at least one mating feature that engages with a corresponding mating feature of dispensing device 50 to ensure accurate mating of dispensing device 50 to cradle 60. For example, in the exemplary embodiment of Figs. 2 and 4, cradle 60 comprises notch 68 that is designed to mate with projection 51 of dispensing device 50. If desired, multiple mating features can be used.

Cradle 60 comprises a charging mechanism that is configured to be able to electrically recharge dispensing device 50 upon device 50 being mated to cradle 60. Such charging mechanisms can include any of the well known methods in the art. Cradle 60 can comprise a power cord; or, it can be wired directly into a wall electrical source.

Cradle 60 can be designed to be attached to a wall (as in the exemplary embodiments of Figs. 2 and 4). Or, cradle 60 can be designed to rest on a horizontal surface (e.g. a countertop). However mounted or attached, cradle 60 can be configured such that when dispensing device 50 is mated to cradle 60, the long axis of dispensing device 50 is in a vertical configuration (as in Figs. 2 and 4); or cradle 60 can be configured such that when dispensing device 50 is mated to cradle 60, the long axis of dispensing device 50 is in a horizontal configuration. Various other features and/or capabilities may be included on test strip 1 , cradle 60, and/or dispensing device 50. For instance, in optical monitoring, it may be useful to include referencing capability to take into account variations in temperature, varying output of light sources 31, varying response of photodetectors 32, background light levels, and the like. Accordingly, in various embodiments reference zones can be included in test strip 1 (in addition to the aforementioned test zones 10). Such reference zones may comprise materials that exhibit a known reflectance at various selected wavelengths or over selected wavelength ranges. As such, optical module 30 can comprise one or more additional light source/photodetector pairs that may be configured to interrogate such reference zones.

With particular regard to the possible effect of the temperature of test strip 1 and/or the oil absorbed therein, on the reflectance signals, it is also possible to include an infrared temperature sensor in the system (for example, in module 30), that is capable of determining the temperature of test strip 1, if it is desired to adjust, correct, etc., the signal based on any effect of temperature.

In another embodiment, in addition to or in place of the inclusion of one or more reference zones on test strips 1 that are used for oil sampling, reference strips may be provided that comprise one or more reference zones. In this case, the methods and devices disclosed herein may be configured such that a reference strip can be brought into proximity to module 30 such that light source/photodetectors pairs can measure reference zones of the reference strip, such that the performance of the system can be evaluated such that any necessary adjustments, recalibrations, etc. may be made. The methods and devices disclosed herein may also be configured such that a reference oil sample (that is, an oil sample comprising a known amount of free fatty acid) can be contacted with a test strip (which may be a standard test strip 1 or an above-described reference strip) such that module 30 interrogates one or more test zones 10 and/or reference zones. The results of this interrogation can be compared to the known value of free fatty acid in the reference oil sample, thus the 30 can be adjusted, calibrated, etc., as deemed necessary.

The systems, methods and devices disclosed herein will include a system 37 for processing the signals received from photodetectors 32 of module 30. Such signals are typically in the form of a voltage generated by a photodetector in response to light incident on the photodetector. Thus, such a photodetector converts an optical signal from test zone 10 to a signal such as voltage, that can then be manipulated, processed, etc. The signal processing system 37 can further comprise one or more analog to digital converters that can provide the voltage signal in a digital form for ease of processing by a microcontroller. In the case of multiple light sources 31, multiple test zones 10, and/or multiple photodetectors 32, a separate voltage signal will typically be provided by each photodetector 32 and which corresponds to each individual test zone 10 interrogated.

Such a signal processing system 37 can reside within dispensing device 50 and/or within cradle 60. Device 50 and cradle 60 can comprise communication capability (e.g., short-range wireless connectivity) such that module 30 can communicate signals to (and receive signals from) signal processing system 37 even if signal processing system 37 is not in the same physical unit as module 30.

Thus in summary, the inventors have found that, upon interrogation of a test zone 10 using methods and devices disclosed herein, a signal may be obtained therefrom. The inventors have further found that a signal resulting from use of a so-called white light LED light source in combination with a relatively broad-band photodiode photodetector (e.g. a signal reflecting the contributions of photons of various wavelengths) may exhibit sufficient change with the amount of free fatty acid in an oil sample, to be useful. Specifically, devices and methods as disclosed herein allow the detection of a change in the optical reflectance of a test zone 10 if the test zone is contacted by an oil which possesses greater than a threshold level of free fatty acid. (The specific threshold level of free fatty acid needed to trigger a response for a given test zone 10 can of course vary, e.g. depending on the amount of base included in the indicator/humectant/base mixture of that zone).

Upon exposure of a test zone 10 to an oil sample containing a free fatty acid level greater than the threshold level for that test zone, a change in optical reflectance of the test zone may be detected. By way of example, a test zone 10 as disclosed herein, when exposed to an oil sample containing a "low" level of free fatty acid (i.e., a level of free fatty acid below the threshold level for that test zone), may, when interrogated, result in a photodiode photodetector emitting a relatively "low" voltage signal (as seen, for example, in the data of Fig. 14). Such a condition will correspond generally to test zone 10 appearing blue upon visual inspection. Such a test zone when exposed to an oil sample containing a "high" level of free fatty acid (above the threshold level for that test zone), may, when interrogated, result in a photodiode photodetector emitting a relatively "high" voltage signal (as seen in Fig. 14). Such a condition will correspond generally to test zone 10 appearing yellow upon visual inspection.

In performing reflectance tests, the inventors have discovered that an "intermediate" level of free fatty acid may be detectable, which is not necessarily visually observable as a condition between "blue" and "yellow", but which nevertheless results in a photodiode detector emitting an "intermediate" signal (as shown in Fig. 14), which is intermediate between, and distinguishable from, the "high" and "low" signals.

Thus in summary, through the methods and devices disclosed herein, the optical interrogation of a test zone 10 may be able to provide more information concerning the free fatty acid content of an oil sample than might otherwise be obtainable (e.g., by visual inspection). Such an ability to obtain more sensitive measurements of individual test zones

10 can be combined with the providing of multiple test zones 10 (which may comprise different levels of base thus may comprise different threshold levels of free fatty acid), so as to allow more accurate, sensitive, and/or precise evaluating of oil quality.

In generating an indication of the oil quality based on optical interrogation of multiple test zones 10, signal processing system 37 may use signals received from all of the test zones (e.g., from all of the photodetectors 32). In a specific embodiment, signal processing system 37 uses (e.g. processes) a combined signal which is a combination of all of the signals from all of the photodetectors 32.

In a one embodiment, the signals from the various photodetectors are integrated (that is, summed or added together). The inventors have found that, upon exposure of multiple test zones 10 to oils containing various concentrations of free fatty acids, an integrated signal from the multiple photodetectors may correlate well with the concentration of free fatty acid in the oil thus can be used in providing an indication of the

011 quality. The use of such an integrated signal, in combination with the fact that each photodetector may be capable of providing a signal corresponding to detection of an "intermediate" level of free fatty acid, may provide improved accuracy, for example without having to use an unpractically large number of individual test zones 10. In a particular embodiment, the signals from the various photodetectors are processed such that the combined signal is a root mean square value (rms value). That is, the signals from the individual photodetectors are all squared, the squared values are processed in combination to determine an average value of the squared values, and the square root of the average squared value is calculated.

Apart from or in addition to the above-mentioned processing, the signals received from the various test zones 10 can be mathematically manipulated (individually or in combination) according to algorithms resident in signal processing system 37 (e.g., loaded into software or firmware) as desired. Thus, either device 50, or cradle 60 (depending on which unit signal processing system 37 resides in) may comprise such components, circuitry, etc., as needed to perform such desired signal processing, and also as needed to control light sources 31 and/or photodetectors 32, and so on. With reference to the block diagram of Fig. 9, signal processing system 37 can operate light sources 31, can operate

(and receive signals from) photodetectors 32, and can process, manipulate, etc., signals received from photodetectors 32. Signal processing system 37 can also perform other functions; for example, it can hold various data and parameters in memory, can communicate with a display or output device, can receive input from a user of the system, can transmit data (e.g. test results) to a central facility, and so on. Signal processing system

37 can comprise a microcontroller, and in a particular embodiment it comprises the type of microcontroller known as a PIC (variously known as a Programmable Interface Controller, or Programmable Intelligent Computer), which may be well suited for the uses described herein. Any or all of the various components of optical module 30 (light sources 31 and photodetectors 32), the components of signal processing system 37, other components such as display screens, input devices, etc., can be connected to, and/or physically mounted on, one or more printed circuit boards present in dispensing device 50 and/or cradle 60. Various other features may be present on either or both of device 50 and cradle 60 (for example, a keypad, buttons or a touch-screen interface for inputting information, an input to initiate the extending of test strip 1 from the dispensing device, and/or an input to release a used test strip 1, etc).

If it is found that certain types of oil display a different signal when interrogated according to the devices and methods disclosed herein (e.g., independent of the amount of free fatty acid in the oil), the systems disclosed herein can include a mechanism wherein a user can input the identity (type) of the oil being tested, so that an automatic adjustment or compensation can be performed, based on the type of oil. In addition, it is also possible to configure the system such that, when a new batch of oil is introduced for cooking, the oil is tested so as to obtain a baseline (reference) reflectance signal which can be stored within the memory of the system 30 and which corresponds to that particular type and/or batch of oil. This stored baseline signal can then be used when the oil is interrogated later, so that automatic adjustment or compensation can be performed based on the particular characteristics of that batch of oil.

Thus in summary, the systems, methods and devices disclosed herein include a system for processing the signals received from the photodetectors and for correlating the signals received from the photodetectors with the free fatty acid content of the oil. They can also include a reporting system for reporting an indication of the oil quality to a user, wherein the indication is associated with (e.g., based on) the free fatty acid content of the oil sample. The indication can be communicated to a user of the system by, for example, a visual or audio signal. Such an indication (or an actual value of the free fatty acid content of the oil, or any other data generated in the course of the signal processing) can also be communicated to an external data collector (for example, a networked computer, etc.) Thus, either dispensing device 50, or cradle 60, or both, can comprise long-range wireless capability to facilitate such ability to transmit (or receive) information. In one embodiment, the indication can be an actual numerical value of the free fatty acid content. Alternatively, the indication can be a parameter that, while not a numerical value of the free fatty acid content, is associated with the free fatty acid content and can serve to allow the user to ascertain the quality of the oil (e.g., whether the oil is still suitable for use). For example, either dispensing device 50, or cradle 60, may have a screen 36 on which is presented a bar graph, the height of which is representative of the amount of free fatty acid. Or, a set or sets of signals (e.g., red, yellow, and green lights) may be may be used to indicate the quality of the oil in terms of free fatty acid content. Or, oil quality information may be presented to the user in a binary (pass/fail) format by (e.g., by way of an audio or visual signal) based on the free fatty acid content.

It may be helpful if the signal processing system comprises information (e.g., stored in electronic memory, firmware or software, for example in a lookup table) which allows the system to correlate the processed signals (e.g., the aforementioned combined or integrated) signals with the free fatty acid content of the oil. Such information can be resident in electronic memory within the system as a fixed value. Or, such information can be periodically updated and/or changed, e.g. by using the system 30 to interrogate one or more standard materials with known amounts of free fatty acid, and/or with known reflectance properties (e.g. reference zones, reference strips, reference oil samples, etc). It may also be advantageous to store other useful information in the system memory; for example, the number of strips remaining in a cartridge, prior test results, and the like. In addition to the systems and methods disclosed above for monitoring of oil quality based on free fatty acid content, it has also been discovered that test strips 1 can be used for monitoring of oil quality based on total polar compound content. Specifically, with reference to Figs. Ia and Ib, it has been discovered that area 20 can be used as a second test zone 20 which can be used to perform a test of the total polar compound content of an oil sample. That is, it has been found that second test zone(s) 20 can absorb oil such that the total polar compound content of the oil can alter the fluorescence properties of the sampling substrate so as to provide the basis for a useful test of the total polar compound content of the oil. In one embodiment, a fluorescent indicator is not provided in second test zone 20, nor is a fluorescent indicator added to the oil sample. Thus, in this case the fluorescent signal is obtained from the oil itself, and/or from the polar compounds found in the oil, and/or from the interaction of the oil and/or the polar compounds with the porous material of the substrate. In this case, the fluorescent signal thus comprises auto fluorescence rather than the measurement of a fluorescent signal from a fluorescent indicator. This is made possible by the discovery that when an oil sample is absorbed into a second test zone 20, an increased amount of total polar compound in the oil sample can cause an increase in the amount of fluorescent light emitted from the oil- containing porous material 5 of second test zone 20. For example, shown in Fig. 15 is that a higher level of total polar compound in an oil sample results in an increased amount of fluorescent light emitted at about 520 nm, when an oil-containing test zone is exposed to incident light at about 470 nm. Of course, many other excitation and/or emission wavelengths may be used in addition to the example shown, for example depending on the type of oil being evaluated.

Thus, in addition to the reflectance measurements described above, an optical interrogation operation can be performed which involves directing light onto at least one second test zone 20 and measuring the fluorescent light emitted therefrom. A system can thus be provided (which may be located on either dispensing device 50 or cradle 60) to perform this operation. In one embodiment, a separate optical module is used to perform the fluorescence interrogation. In an alternative embodiment, the optical interrogation via fluorescence of zone(s) 20 is performed by the same optical interrogation module 30 that is used for the optical interrogation (by reflectance) of zones 10. Thus, with reference to Fig. 7, in one embodiment optical interrogation module 30 comprises at least one light source 41 for directing light onto at least one test zone 20 of test strip 1, and at least one photodetector 42 for measuring fluorescent light emitted from the at least one test zone 20.

In a particular embodiment, the at least one light source 41 and the at least one photodetector 42 are spatially arranged in combination with light sources 31 and photodetectors 32, such that light sources 31 and photodetectors 32 correspond to the spatial arrangement of first test zones 10, and light source(s) 41 and photodetector(s) 42 correspond to the spatial arrangement of second test zone(s) 20. For example, in the exemplary arrangement shown in Figs. 1 and 7, module 30 comprises four light sources 31a, 31b, 31c and 3 Id for reflectance interrogation, and one light source 41 for fluorescence interrogation. Test strip 1 has four test zones 10a, 10b, 10c and 1Od, that receive light from sources 31 , and one second test zone 20 that receives light from source

41. Thus in one embodiment, light sources 31 and 41 are spatially arranged so as to correspond to the spatial arrangement of zones 10 and 20 such that light can be directed onto all of the first zones 10, and onto the at least one second zone 20, without having to move test strip 1 and module 30 relative to each other. Light source 41 may comprise any of a variety of light sources such as those mentioned previously with respect to light source 31. For use in fluorescence interrogation, it may be advantageous for light source 41 to emit light in a narrow wavelength range. This may be achieved by the use of, for example, an LED that emits light in a narrow wavelength range. Or, it may be achieved by the use of a fairly broad band light source, but with the use of filters to narrow the wavelength prior to the light being directed onto test zone 20.

Photodetector 42 may comprise any of a variety of devices capable of measuring the number of incident photons, including those mentioned earlier with regard to photodetectors 32. Photodetector 42 can be selected or configured to detect light of a specific, relatively narrow wavelength range. Such ability may be particularly useful in interrogation via fluorescence; for example, in enabling photodetector 42 to detect fluorescent light emitted by second test zone 20 in a certain wavelength range, while not detecting light reflected by second test zone 20 in a different wavelength range, not detecting ambient light in a different wavelength range, etc.

Photodetector 42 can be configured in module 30 so as to be able to receive an emitted fluorescent signal from second test zone 20 upon the use of light source 41 to direct light onto second test zone 20. In module 30, photodetector 42 can be placed in proximity to light source 41, for example in the general manner shown in Fig. 8. In one embodiment, photodetector 42 is placed behind cover 33 of module 30, with cover 33 comprising an optically transmissive portion 45 over photodetector 42, such that at least a portion of the fluorescent light emitted from second test zone 20 may be detected by photodetector 42. Optically transmissive portion 45 can be angled in a similar manner to that of optically transmissive portion 35 (shown in Fig. 8), or can be made somewhat larger than the light-sensitive surface of photodetector 42 (e.g., as shown in Fig. 7), so as to not block any portion of the emitted fluorescent that would otherwise reach photodetector 42, while minimizing the amount of ambient light that reaches photodetector 42. Similarly, optically transmissive portion 44 over light source 41 can be likewise configured, if desired.

It may be useful to configure module 30 to maximize the amount of fluorescent emitted light from second test zone 20 that is received by photodetector 42, while minimizing the amount of light reflected from second test zone 20 that is received by photodetector 42. This may be done in several ways. For example, as already mentioned herein, either or both of light source 41 and photodetector 42 can emit/detect (respectively) light in a fairly narrow wavelength range. For example, light source 41 may emit light in a relatively narrow band centered around 480 nm. Photodetector 42 may detect light in a relatively narrow band centered around 520 nm. Thus, fluorescent light emitted by second test zone 20 at around 520 nm in wavelength may be detected by photodetector 42, while light reflected from test zone 20 at around 480 nm in wavelength may not be detected by photodetector 42. Such wavelength-based filtering can also be achieved by providing an optically transmissive portion 44 over light source 41, and/or an optically transmissive portion 45 over photodetector 42, that is transmissive only to desired wavelength ranges. For example, a filter (which may comprise a film, a coating, etc.) may be used that allows light only of a certain wavelength to be passed (e.g., a bandpass filter, monochromatic filter, dichroic filter, dichroic reflector, etc). Or, a combination of longpass and shortpass filters can be used to similar effect. Such filters can, in addition to being wavelength dependent, can be angle dependent (for example, so as to block ambient light).

It may also be possible to maximize the emitted fluorescent light detected, and minimize the detection of ambient and/or reflected light, by the physical arrangement of light source 41 and photodetector 42. Thus, although generally represented in Fig. 8 as configured in a generally coplanar configuration, light source 41 and photodetector 42 can be positioned on module 30 in an angled configuration. Various such configurations are possible as is known in the art. It may also be possible to configure the light source and photodetector using confocal principles to maximize the amount of fluorescent light detected relative to reflected and/or ambient light.

In generating an indication of the total polar compound content, the systems disclosed herein will use signals received from the one or more second test zones 20 (e.g., from photodetector(s) 42). The signals received from photodetector(s) 42 may be processed by signal processing system 37 so as to provide an indication of oil quality based on the total polar compound content of the oil. Thus, two separate indications of oil quality, one associated with free fatty acid content and the other with total polar compound content, may be presented to a user. Alternatively, the free fatty acid and total polar content indications may be combined into a single indication of oil quality that takes into account contributions from both free fatty acids and total polar compounds.

Other features and functionalities described previously herein (use of reference zones, use of reference oil samples, programming of the system to take into account the specific type of oil used, and the like), can be used with regard to the fluorescence-based interrogation of test zones 20, in similar manner to those discussed with regard to reflectance-based testing.

Examples

Example 1 Test strips were obtained that are available from 3M Company under the designation 3M Shortening Monitor Test Strips, and that are believed to be manufactured in similar manner to methods described in US Patent 4,654,309, Example 4. Cooking oil was obtained that had a composition of approximately 40% sunflower oil (minimum 70% oleic acid), approximately 30% palm oil, and approximately 30% hydrogenated rapeseed oil (all percentages by weight). The cooking oil was used in cooking french fries for a period of about two months, over which time small samples were periodically removed from the oil.

The samples were tested by the following procedure. Since most of the samples were solid at room temperature, each sample (150 cc in plastic jars) was heated in a microwave oven for 60 seconds or until the sample melted to form a liquid. A test strip was then dipped into the oil sample, then placed onto a paper towel to remove any excess oil. The optical reflectance of each of the four test zones of the strip (i.e., the zones that were blue in appearance as the strip was received) was then measured using a QuadScan Reflectance Photometer (Model 100, available from KGW Enterprises, Elkhart, IN). Optical filters were used so as to interrogate the zones at specific wavelength ranges: the blue wavelength corresponded to a wavelength range of approximately 400-510 nm, the green wavelength 510-586 nm, the red wavelength 586-660 nm, and the infrared (IR) wavelength 825-855 nm.

The optical reflectance of the four test zones was measured by traversing the test strip relative to the reflectance photometer such that the interrogation unit of the photometer interrogated each of the test zones in succession. (Readings were taken over the entire test strip, including blank areas between the test zones, but readings from the blank areas in between the test zones were not used.) The strip was shielded from ambient light during this process. Typically, for each strip the reflectance readings from the four test zones were averaged together. Thus, in the plots of Figs. 10-13, each data point typically represents the averaged reflectance of four test zones of a test strip. For the various oil samples, the free fatty acid concentration was estimated, by standard (visual) use of 3M Shortening Monitor Strips in accordance with the product instructions. According to the product instructions, visually obtained results will fall into one of the following categories: free fatty acid content of less than 2%; free fatty acid content of 2% to less than 3.5%; free fatty acid content of 3.5% to less than 5.5%; free fatty acid content of 5.5% to less than 7%; or, free fatty acid content of greater than 7%.

Plots (Figs. 10-13) were then produced in which the measured reflectance (obtained via interrogation in different wavelength ranges) was plotted against the free fatty acid content as estimated by visual use of the product. Within these general groupings of data (e.g., within the group with 3.5-5.5% free fatty acid content, the group with 5.5-7.0% free fatty acid content, etc.) it was also possible to at least qualitatively rank the individual oil samples according to their estimated free fatty acid content. This could be done, for example, according to the known length of time that a particular oil sample had been in use (which would be expected to increase the free fatty acid content); or, according to the content of total polar compounds in the sample, as measured according to method ISO 8420 (of which free fatty acids comprise a portion and thus would be expected to at least generally correlate with); or, according to the brightness or intensity of the visually observed test zones. Thus, within the general groupings of the data in Figs. 10-13, the data within each grouping are arranged such that samples with lower estimated free fatty acid content are toward the left hand side of the group, and samples with higher estimated higher free fatty acid content are toward the right hand side of the grouping. No attempt at quantification of specific concentrations of free fatty acid should be inferred, however. For convenience of presentation, the data is broken up into four plots. Fig. 10 contains data from interrogation in the infrared wavelength range; Fig. 11 contains data from interrogation in the red wavelength range; Fig. 12, green; and Fig. 13, blue. In general, the reflectance data indicates that, in these experiments, interrogation in the red or green wavelength range provided a larger response than did interrogation in blue or infrared wavelength range.

Example 2

Test strips were obtained that are available from 3M Company under the designation 3M Shortening Monitor Test Strips, and that are believed to be manufactured in similar manner to methods described in US Patent 4,654,309, Example 4. Four photodetector photodiodes (type Si PIN) were obtained from Hamamatsu

Photonics, Hamamatsu City, Japan, under the designation S9345. The individual photodiodes were labeled PD-O, PD-I, PD-2, and PD-3.

Light emitting diodes (type Super- White (GaN) were obtained from SuperBright LEDs, Inc, of St. Louis, Missouri, under the designation RL5-W5020. Test strips were obtained that are available from 3M Company under the designation 3M Shortening Monitor Test Strips, and that are believed to be manufactured in similar manner to methods described in US Patent 4,654,309, Example 4. Test zones from various test strips were contacted with oil samples containing a "Low" amount of free fatty acid; that is, an amount that, for these test zones, would not trigger a visual change (blue color to yellow color) noticeable to a typical human user. The test zones were then interrogated by way of directing light from the LEDs onto the test zones, and measuring reflected light therefrom by way of the photodiodes (with the LEDs and photodiodes being configured and operated in accordance with manufacturers recommendations and by methods well known in the art). For the four individual photodiodes, the resulting output voltage is presented in Fig 14 (labeled "Low Free Fatty Acid"). Other test zones were contacted with oil samples containing a "High" amount of free fatty acid; that is, an amount that, for these test zones, would trigger a visual change (blue color to yellow color) noticeable to a typical human user. The test zones were then interrogated by use of the LEDs and the photodiodes as described above, with the resulting output voltage from the photodiodes presented in Fig 14 (labeled "High Free Fatty Acid"). Other test zones were contacted with oil samples containing a "Medium" amount of free fatty acid. This was believed to be an amount that, for these test zones, might not reliably trigger a visual change (blue color to yellow color) noticeable to a typical human user. The test zones were then interrogated by use of the LEDs and the photodiodes as described above, with the resulting output voltage from the photodiodes presented in Fig 14 (labeled "Medium Free Fatty Acid").

As presented in Fig. 14, interrogation of test zones using the methods and apparatus described above, allowed the obtaining of an "intermediate" signal which could be distinguished from a signal corresponding to a "low" state (i.e. a state in which the test zones appeared visually blue), and from a signal corresponding to a "high" state (i.e. a state in which the test zone appeared visually yellow).

Example 3

Test strips were obtained that are available from 3M Company under the designation 3M Shortening Monitor Test Strips, and that are believed to be manufactured in similar manner to methods described in US Patent 4,654,309, Example 4. Cooking oil was obtained that had a composition of approximately 40% sunflower oil (minimum 70% oleic acid), approximately 30% palm oil, and approximately 30% hydrogenated rapeseed oil (all percentages by weight). The cooking oil was used in cooking french fries for a period of about two months, over which time small samples were periodically removed from the oil.

The samples were tested by the following procedure. Since most of the samples were solid at room temperature, each sample (150 cc in plastic jars) was heated in a microwave oven for 60 seconds or until the sample melted to form a liquid. A test strip was then dipped into each oil sample, then placed onto a paper towel to remove any excess oil. Fluorescence measurements were performed on various oil-containing "blank" areas of the test strips (that is, on areas that did not have free fatty acid-sensitive impregnated materials), using an ESE XYZ Stage Scanner (Embedded System Engineering GmBH, Stockach, Germany) operating at an excitation wavelength of approximately 470 nm and an emission wavelength of approximately 520 nm.

For each oil sample, multiple readings were taken in different blank areas of each test strip. An average of these multiple readings was reported. Typically, several strips were tested by this procedure, for each oil sample. These data are shown in Fig. 11, plotted as a function of the total polar compound concentration (as determined using a procedure similar to that outlined in ISO Standard 8420) of the oil.

The tests and test results described above are intended solely to be illustrative, rather than predictive, and variations in the testing procedure can be expected to yield different results. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom.

The present invention has now been described with reference to several embodiments thereof. It will be apparent to those skilled in the art that changes can be made in the embodiments described without departing from the scope of the invention. Thus, the scope of the present invention should not be limited to the exact details and structures described herein, but rather by the structures described by the language of the claims, and the equivalents of those structures.

Claims

Claims

1. A device for dispensing a test strip and for optically interrogating the test strip, the device comprising: a housing containing at least one test strip, wherein the test strip comprises a plurality of test zones each comprising an optical property that is responsive to the free fatty acid content of an oil sample; a mechanism for extending a portion of the test strip out of the device housing such that the plurality of test zones are exposed; an optical interrogation module for optically interrogating each of the test zones by a first optical mechanism and receiving signals therefrom; and, a system for processing the received signals and correlating the received signals with the free fatty acid content of the oil sample.

2. The device of claim 1 wherein the processing and correlating system is configured to sum together the signals from the test zones to form an integrated signal and to correlate the integrated signal with the free fatty acid content of the oil sample.

3. The device of claim 1 wherein the processing and correlating system is configured to process the signals from the test zones to form a root mean square value and to correlate the root mean square value with the free fatty acid content of the oil sample.

4. The device of claim 1 wherein the test zones each comprise an indicator whose optical absorbtive/reflective properties are responsive to the free fatty acid content of the oil sample, and wherein the optical interrogation of the test zones comprises measurement of reflectance.

5. The device of claim 1 wherein the device further includes a reporting system for reporting an indication of the oil quality, wherein the indication is associated with the free fatty acid content of the oil sample.

6. The device of claim 1 wherein the optical interrogation module comprises separate light sources for directing light onto each test zone, and separate photo detectors for detecting light reflected from each test zone.

7. The device of claim 6 wherein the optical interrogation module is movable between a first, secured position, and a second, extended position, wherein when the module is in the second, extended position the separate light sources and the separate photodetectors of the optical module are aligned with the test zones of the test strip such that the test zones can be optically interrogated.

8. The device of claim 1 wherein: the test strip further comprises at least one second test zone comprising a second optical property that is responsive to the total polar compound content of the oil sample; and wherein the device further comprises: a system for optically interrogating the at least one second test zone by a second optical mechanism that is different from the optical mechanism used to interrogate the plurality of test zones, and receiving a signal therefrom, and, a system for correlating the received signal from the at least one second test zone with the total polar compound content of the oil sample.

9. The device of claim 8 wherein the second optical mechanism comprises measurement of fluorescence.

10. The device of claim 8 wherein the device further includes a reporting system for reporting an indication of the oil quality, wherein the indication is associated with the total polar compound content of the oil sample.

11. A system for dispensing a test strip and for optically interrogating the test strip, the system comprising: a dispensing device containing: at least one test strip, wherein the test strip comprises a plurality of test zones each comprising an optical property that is responsive to the free fatty acid content of an oil sample; a mechanism for extending a portion of the test strip out of the dispensing device such that the plurality of test zones are exposed; and, a cradle adapted for receiving the dispensing device, wherein the cradle comprises an optical interrogation module for optically interrogating each of the test zones by a first optical mechanism and receiving signals therefrom, and, a system for processing the received signals and correlating the received signals with the free fatty acid content of the oil sample.

12. The system of claim 11 wherein the processing and correlating system is located within the cradle.

13. The system of claim 11 wherein the processing and correlating system is configured to sum together the signals from the test zones to form an integrated signal and to correlate the integrated signal with the free fatty acid content of the oil sample.

14. The system of claim 11 wherein the processing and correlating system is configured to process the signals from the test zones to form a root mean square value and to correlate the root mean square value with the free fatty acid content of the oil sample.

15. The system of claim 11 wherein the test zones each comprise an indicator whose optical absorbtive/reflective properties are responsive to the free fatty acid content of the oil sample, and wherein the optical interrogation of the test zones comprises measurement of reflectance.

16. The system of claim 11 wherein the device further includes a reporting system for reporting an indication of the oil quality, wherein the indication is associated with the free fatty acid content of the oil sample.

17. The system of claim 11 wherein the optical interrogation module comprises separate light sources for directing light onto each test zone, and separate photodetectors for detecting light reflected from each test zone.

18. The system of claim 11 wherein: the test strip further comprises at least one second test zone comprising a second optical property that is responsive to the total polar compound content of the oil sample; and wherein the cradle further comprises: a system for optically interrogating the at least one second test zone by a second optical mechanism that is different from the optical mechanism used to interrogate the plurality of test zones, and receiving a signal therefrom, and, a system for correlating the received signal from the at least one second test zone with the total polar compound content of the oil sample.

19. The system of claim 18 wherein the second optical mechanism comprises measurement of fluorescence.

20. The system of claim 18 wherein the system further includes a reporting system for reporting an indication of the oil quality, wherein the indication is associated with the total polar compound content of the oil sample.

21. A method of evaluating the quality of oil, the method comprising: providing oil that potentially comprises free fatty acid content; providing a dispensing device containing at least one test strip, and a cradle adapted to receive the dispensing device, wherein the test strip contains a plurality of test zones, wherein each test zone is responsive to free fatty acid; extending a portion of the test strip out of the dispensing device such that the plurality of test zones are exposed, contacting the oil with the test strip such that the oil is brought into contact with at least a portion of each of the test zones; aligning the plurality of test zones with an optical interrogation module comprising light sources and photodetectors; interrogating the plurality of test zones so as to receive signals therefrom; processing the received signals; correlating the received signals with the free fatty acid content of the oil; and, reporting an indication of the oil quality of the oil, wherein the indication is associated with the free fatty acid content of the oil.

22. The method of claim 21 wherein the optical interrogation module is located on the dispensing device and is movable between a first, secured position, and a second, extended position in which the light sources and photodetectors of the optical interrogation module are aligned with the test zones of the test strip.

23. The method of claim 21 wherein the optical interrogation module is located on the cradle and is configured such that when the cradle receives the dispensing device, the light sources and photodetectors of the optical interrogation module are aligned with the test zones of the test strip.

24. The method of claim 21 wherein when the portion of the test strip is extended out of the device such that the plurality of test zones are exposed, a second portion of the test strip is securely held within the device; and, when the test strip is contacted with oil and when the plurality of test zones are interrogated, the second portion of the test strip continues to be securely held within the device.