Short title: Method for preparing a protein-based, fibre- comprising food product, and fibre-comprising food product obtained
The invention relates to a method for preparing a protein-based, fibre-comprising food product, in which:
1) a hydrocoUoid that precipitates with metal cations and a composition comprising vegetable protein material are mixed with one another in aqueous solution,
2) the composition from 1) is made into a homogeneous mixture,
3) the homogeneous mixture from 2) is brought into contact with an aqueous solution of a metal cation with a valency of at least 2 to form a product which comprises fibres comprising precipitated hydrocoUoid and vegetable protein material, and
4) the product formed is recovered.
A method of this type is known from NL-C 1008364 in the name of A.C. Kwelda .
It is an object of the present application to provide a specific range of applications for this method, and to this end the method is characterized in that the homogeneous mixture from 2) is converted into a selected three-dimensional shape with the aid of a shaping process and this shape is then brought into contact with the aqueous solution comprising metal cations.
This is because it has been found that the method described in the abovementioned patent publication can be carried out in such a manner that a fibre-comprising food product is obtained in a selected three-dimensional shape which is matched to the type of shapes to which the customer is accustomed and/or it is possible to create a shape which the consumer has not previously seen and/or has not expected for a product of this type.
The method- as described above in accordance with the invention comprises a number of steps and expediently incorporates, in particular in step 1) , a refinement which leads to favourable
results in terms of controllability of the method.
In a first variant, in step 1) an aqueous solution of a hydrocoUoid that precipitates with metal cations is made, and this solution is introduced into a liquid composition comprising vegetable protein material and water. This is because it has been found that in terms of controllability of the method, forming an aqueous solution of a hydrocoUoid that precipitates with metal cations first of all and adding this solution to a liquid composition that comprises vegetable protein material and water leads to better controllability of the method, and in particular prevents lumps of the hydrocoUoid from forming. As will be explained in more detail below, this method embodiment reduces the quantities of raw materials required.
On the other hand, it is, of course, also possible, in the first step of the method, simply to mix the vegetable protein material, a hydrocoUoid that precipitates with metal cations and water with one another directly in the desired ratio, in which case the formation of lumps is avoided by careful metering and vigorous stirring.
One particular embodiment of the present method is characterized in that the aqueous solution of a hydrocoUoid that precipitates with metal cations and a composition comprising vegetable protein are mixed with one another in the presence of a quantity of a phosphate material.
The use of a phosphate material is described in PCT application PCT/NL02/00594 in the name of the present Applicant, which was not published before the filing date of the present application. The abovementioned PCT application describes a method which has similarity to the method disclosed by the present application; the protein material which forms the starting point, however, is a milk protein material and not a vegetable protein material, and furthermore the use of a treatment to make the homogeneous mixture into a selected three-dimensional shape, which is crucial to the present application, is not present in the abovementioned application.
The abovementioned PCT application uses phosphate material for various purposes; one of these purposes is to digest the protein material used. The action of the phosphate material in the digestion manifests itself in an improved ability of the fibres comprising precipitated hydrocolloid/milk protein material formed to take up water and an improved mouthfeel of the product comprising fibres of this nature.
It has been found that a digestive action of this nature on the part of a phosphate material also occurs with a vegetable protein material which is selected as the starting material for the present application.
It has been found that by adding suitable quantities of a phosphate material, it is possible to control the ability of the fibrous product formed to take up water as desired. If the fibres are prepared without the presence of phosphate, water contents of 10-45% by weight, preferably 20-40% by weight and in particular 28-38% by weight, are formed. If phosphate is added, it is possible to reach water contents of up to 80-85%.
When the homogeneous mixture which is formed in step 2) of the method is obtained, this mixture, according to the present invention, is made into a selected three-dimensional shape.
The person skilled in the art will be aware of numerous shaping processes for making the homogeneous mixture into a desired three-dimensional form. Mention may be made of a method in which the homogeneous mixture is fed under pressure to a strand- forming head or a ball-forming device. As an alternative to the pump and a strand-forming head, it is also possible to use an extruder.
In the first embodiment, the homogeneous mixture is discharged into the aqueous solution of a metal cation with a valency of at least 2, so as to form a strand which, at least at the surface, comprises hydrocoUoid that has precipitated with metal cations. The homogeneous mixture comprises vegetable protein material,
hydrocoUoid that precipitates with metal cations and optionally a phosphate material; discharging the strand which is formed into an aqueous solution that contains metal cations with a valency of at least 2 causes the strand which is formed to harden, starting at the surface, through precipitation of the hydrocoUoid with metal cations. The skin of precipitated hydrocoUoid and vegetable protein material formed on the strand forms a barrier to diffusion of metal cations to the interior of the strand; obviously, it is possible for all the hydrocoUoid in the strand to be precipitated if the contact with the aqueous solution of metal cations is maintained for long enough and/or the ion concentration is made sufficiently high.
In particular, however, the strand, after it has been formed, is rinsed with water in order to wash out metal cations with a valency of at least 2 that have not yet reacted with hydrocoUoid. Thorough rinsing with water, such as tap water, causes the metal cations that are present in excess to be rinsed out of the surface of the strand, so that no further hydrocoUoid precipitation can occur. The result is a strand of vegetable protein material/hydrocolloid/phosphate and moisture which has to a certain extent a hard surface layer, while the core still has the consistency of the original homogeneous mixture .
With regard to the metal cations which can be used, these cations will generally be provided in the form of water-soluble calcium or magnesium salts or mixtures thereof. Suitable calcium salts include calcium chloride, calcium acetate and calcium gluconate, although other calcium or magnesium salts which are permitted for use in the food industry can also be used.
The concentration of metal cations used in the precipitation solution is generally, for example in the case of calcium chloride, from 0.1-15% by weight, expediently 0.5-8% by weight and preferably 4-8% by weight.
To set the properties of the desired end product, it is expedient for the homogeneous mixture, before it is subjected to a forming process, to be mixed with desired additives in order
to set the properties of the food product to be formed, which properties are selected from flavour, odour, colour and consistency.
Many types of additives can be selected, such as broth, dairy product, processed dairy product, flavourings, fruit juice and of course also mixtures of two or more such materials. This list is not exhaustive, since all kinds of possible additives which are not included in the above list will be obvious to the person skilled in the art.
In one attractive embodiment, the material in strand form which is formed is cut into pieces and dried to form an instant food product. The term instant food product is to be understood as meaning a product which is available to the consumer in dry form and which takes up moisture by being mixed with hot or cold water, so that it acquires the consistency which is desired for consumption.
The strand-like material described above that had been cut into pieces was able to take up moisture by softening in water for 5 to 10 minutes to a sufficient extent for the soft consistency of the core to be fully restored. It is also possible to choose not to dry the strand-like material after it has been cut into pieces, but rather to package it directly in order for it to be offered to the consumer as a fresh product.
In another attractive embodiment, the homogeneous mixture is shaped into ball shaped pieces, and these pieces are then brought into contact with the abovementioned metal cation solution.
As before, it is possible to select a residence time for the ball shaped pieces in the metal cation solution and/or the presence of residual metal cations on the surface of the ball shaped pieces in such a manner that complete precipitation of the hydrocoUoid that is sensitive to metal cations occurs.
On the other hand, by washing the ball shaped pieces with water,
it is possible to ensure that the excess of metal cations is removed, so that ball shaped pieces are obtained with a skin in which there is precipitated hydrocoUoid, while the core of the ball shaped pieces comprises hydrocoUoid which is not precipitated with metal cations.
In the case of the ball shaped pieces too, it is possible to add additives to the homogeneous mixture as described above. In this case, the additives may also be formed by, for example, pieces of vegetables, such as courgette or spinach; pieces of fruit, etc.
With regard to the use of additives to set properties such as flavour, odour, colour and consistency, it should also be noted that it is expedient for the homogeneous mixture to be mixed therewith prior to its forming treatment. The additives may obviously also be added after the forming operation has been carried out and/or the hydrocoUoid precipitation step has been carried out. In the latter case, it is possible in particular for liquid additives to be impregnated into the shaped food products which have been provided at least with a hardened skin and comprise fibres containing vegetable protein, hydrocoUoid, phosphate and metal cations, such as calcium.
If the composition comprising vegetable protein material is not in a specific form, the vegetable protein material may be selected from the protein materials of: soya, lupin, rice, maize, potato, beans,. peas, wheat, barley, oats, rye and tapioca.
The phosphate material is selected from the alkali metal and ammonium salts of phosphoric acid and polyphosphoric acid, such as disodium hydrogen phosphate, trisodium phosphate or sodium hexametaphosphate, trisodium phosphate or sodium polyphosphate (NaP03)n, where n ~ 25.
The quantity of phosphate material is at least sufficient to digest the vegetable protein material, and is in particular from 0.1 to 1.5% by weight, based on the total of all the
constituents of the homogeneous mixture.
The hydrocoUoid that precipitates with metal cations may be selected from pectin with a low methoxyl group content, Gellan gum and alginate; of these, sodium alginate is preferred. The hydrocoUoid that precipitates with metal cations is generally present in a quantity of from 0.1-10% by weight, based on the total of all the constituents of the homogeneous mixture.
The pH of the homogeneous mixture of vegetable protein material, hydrocoUoid that precipitates with metal cations, phosphate material and water is set to a pH of between 4 and 8.
If a first type of structure of the food product is desired, the pH is set to between 5.0 and 7.5. The first type of structure is a relatively hard material with relatively long fibres.
If a second type of structure, which is softer with shorter fibres, is desired, the pH of the homogeneous mixture is set to between 4.5 and 6.0.
In connection with the above, it should be noted that a higher pH of the homogeneous mixture is slightly preferred, since in this case the water binding activity is higher than at a lower pH.
The invention also relates to a protein-based, fibre-comprising food product obtained with the aid of a method as described- above, which is characterised in that the food product is packaged.
It is expedient for the fibre-comprising food product according to the invention to be subjected to a treatment with a germicidal action before and/or after it has been packaged. A treatment with a germicidal action can be selected from pasteurization, sterilization, treatment with radiation, such as γ radiation and the like. However, it is expedient for the treatment with a germicidal action, such as for example pasteurization, to be carried out after packaging of the fibre-
comprising food product. Pasteurization may take place at a temperature of 60-90°C for 5-45 in, for example a temperature of 90°C for 45 minutes.
If the homogeneous mixture is prepared at temperatures of > 70 °C and the fibre-forming step is also carried out at this temperature, there is generally no need for any treatment with a germicidal action.
The invention also relates to a fibre-comprising food product obtainable by the method according to the invention as described above .
In the method according to the invention as described above, a homogeneous mixture of protein, optionally phosphate material, hydrocoUoid that precipitates with metal cations and water is generally prepared by stirring at a temperature in the range from 20 to 90°C, more particularly from 30 to 90°C, and generally at a temperature of approximately 50 °C.
At a slightly elevated temperature, the protein will melt or be liquefied and will form a homogeneous mixture with the hydrocoUoid that precipitates with metal cations and water.
It should be noted that the present application uses the term homogeneous mixture to encompass emulsions, dispersions and solutions .
With proteins with a low melting point, if an elevated temperature is used melting will occur, so that the homogeneous mixture represents a distribution of two liquid materials which are not soluble in one another, i.e. an emulsion. With other proteins, there will be no melting, but rather dispersion or dissolution will occur.
A number of different embodiments of the preparation of a homogeneous mixture are explained below.
Example :
A product selected from: soya protein isolate, Supro 515 (92% by weight protein; 0.128% by weight calcium) produced by Dupont Protein Technology International and Lupin protein, Vitaprot lupin protein LP 60 (50% by weight protein; 0.1% by weight calcium) produced by J. Rettenmaier & Sδhne, is used as vegetable protein material.
To prepare a homogeneous mixture, 92.4 g of one of the said proteins, together with a desired quantity of sodium polyphosphate (NaP03)n, where n ~ 25, were added to 1100 g of water at approximately 70 °C. Stirring for at least 10 and at most 15 min created a protein emulsion. The pH of the emulsion was determined to be 7.1. The mixture obtained was introduced into a high-speed mixture and 40 g of sodium alginate (Kelco, Manugel DMB) were added in dry form. The viscous, homogeneous mixture obtained had a mayonnaise-like character and was discharged into 4% strength by weight CaCl2 solution in water. Strands or ball shapes were obtained, depending on the method selected for creating the three-dimensional shape.
The influence of the quantity of phosphate was investigated in a number of tests working on the basis of soya protein isolate.
The following results were obtained:
Sodium polyphosphate Contact time Strength of skin (g/1232 g of sec ) after 24 hours homogeneous mixture) a) 0 2 soft b) 0 5 soft c) 0 20 hard d) 1.0 5 softer than b) e) 1.0 20 less hard than c) f) 12 10 softer than b)
In the tests, strands were formed with a diameter of 2 mm; the washing time in water after contact with the 4% strength by weight CaCl2 solution was 120 sec.
These tests show that the quantity of phosphate material present in the homogeneous mixture is a crucial factor for the hardness properties of the skin, formed through contact with the calcium chloride solution, of vegetable protein/precipitated alginate fibres .
The fibres formed using a phosphate material, after they had been shaped and the excess adhering water had been removed, have a moisture content of up to 80-85% by weight.
Strands or ball shapes are obtained depending on the method selected for creating the three-dimensional shape. By using co- extrusion, it is also possible to opt to apply the homogeneous mixture as a sheath around a liquid, pasty or solid core made from a material with a composition which differs from the composition of the homogonous mixture. Subsequently bringing the product formed in this way into contact with an aqueous solution of a metal cation with a valency of at least 2 creates a product with a core which can be formed as desired and a sheath which, at least on the outer side, comprises vegetable protein/precipitated hydrocoUoid fibres.