WO1990006688A1

WO1990006688A1 - Improved process for extracting espresso coffee

Info

Publication number: WO1990006688A1
Application number: PCT/US1989/005663
Authority: WO
Inventors: Howard W. Selby, Iii
Original assignee: Selby Howard W
Priority date: 1988-12-12
Filing date: 1989-12-11
Publication date: 1990-06-28
Also published as: CA2005099A1; AU4753790A

Abstract

An improved process for the extraction of espresso coffee from ground coffee beans in which the pressure of extraction is precisely regulated by a pressure valve and is not dependent on coffee grind size or degree of compaction of the coffee grind.

Description

IMPROVED PROCESS FOR EXTRACTING ESPRESSO COFFEE

Background of the Invention

Field of Invention

This invention relates generally to extracting espresso coffee and specifically to an improved process of extracting espresso coffee in which the extraction pressure is precisely regulated.

Description of Prior Art

Espresso coffee is brewed by forcing hot water through finely ground coffee beans under high pressure which extracts the coffee from the coffee beans. Both the amount of ground coffee beans and water are volumetrically measured. For the coffee to be properly extracted there must be a pressure differential across the ground coffee beans.

In conventional espresso machines, the coffee beans are finely ground then volumetrically measured and packed in a filter device. The filter is then attached to the espresso machine. A measured volume of hot water is forced through the filter by means of a volumetric piston displacement pump which is hand operated or by means of an electric pump device. The hot water is forced into the ground coffee beans in the filter. The fineness of the coffee grind and the degree of compaction creates a pressure differential across the ground coffee beans. The pressure differential varies across the ground coffee beans being highest on the upstream side of the ground coffee beans and lowest on the downstream side. Because of the pressure gradient, not all of the ground coffee beans are subjected to the optimum extraction pressure resulting in extraction inefficiencies which require larger volumes of ground coffee beans to be used. The water, under pressure, is forced through the ground coffee beans and extracts the coffee from the beans. Extraction time is very short compared to other coffee brewing methods. The extracted coffee drains through an opening in the bottom of the filter and is collected in a cup for consumption. The pressure differential in the filter is directly related to the grind of the coffee beans and the degree of their compaction.

The quality of the extracted coffee is a function of the following: the freshness of the coffee beans; the fineness of the grind; the volume of ground coffee beans; the compaction of the ground coffee beans; the volume of water; the temperature of the water; and the extraction pressure. The degree of compaction of the ground coffee beans and thus the resulting extraction pressure are controlled by the espresso machine operator so operator skill plays an important part in the quality of the coffee produced.

In France and Italy, where espresso coffee has been popular for many years, there are many skilled espresso machine operators. The chances of obtaining a high quality of espresso coffee from such operators is high. In other countries where espresso coffee is growing in popularity, there are not many skilled operators and the resultant quality of espresso coffee suffers.

It would be desirable to have an espresso coffee extraction process that did not rely on operator skill to produce high quality espresso coffee.

In view of the foregoing, it is an object of this invention to provide an improved espresso coffee extraction process in which the extraction pressure is precisely regulated by the espresso machine and is not a function of operator skill. It is a further object of this invention to provide an improved espresso coffee extraction process in which the pressure for coffee extraction is kept constant throughout the ground coffee beans resulting in optimum extraction from all the ground coffee beans.

It is a further object of this invention to provide an improved espresso coffee extraction process in which a range of coffee bean grinds sizes can be accommodated.

Summary of the Invention

These and other objects of the invention are accomplished in accordance with the principles of the invention by use of an espresso coffee extraction process in which the extraction pressure necessary to produce high quality espresso coffee is not dependent on the compaction of the ground coffee beans by the operator. The pressure is controlled by a pressure valve on the outflow of the filter which holds the ground coffee beans.

As in the conventional espresso coffee extraction process, the volume of ground coffee and the volume of water forced through the ground coffee are volumetrically measured. Unlike the conventional process, however, the fineness of the coffee grind used in the improved process can range from a fine espresso grind to a coarser or finer coffee grind. In addition, in the improved process, the ground coffee beans need not be compacted.

A measured volume of water, either hot or cold, is forced through the ground coffee beans as in a conventional process. In the conventional process the pressure required to extract the coffee from the ground beans is created by the compacted coffee grinds which restricts the flow of water through the coffee grinds until the water pressure is high enough to penetrate the barrier created by the compacted ground coffee. The pressure varies throughout the ground coffee beans being highest on the side of the ground coffee of water inflow decreasing to zero pressure at the water outflow point.

In the improved process, however, the requisite pressure results from a mechanical valve on the outflow of the filter. A measured volume of water is introduced into the filter which holds the ground coffee beans. When the pressure reaches the optimum pressure for extraction, the valve regulator opens allowing the water to pass through the ground coffee beans. The pressure throughout all the ground coffee beans is the same - there is no pressure gradient. Because the optimum extraction pressure extends to all of the ground coffee beans, less ground coffee beans are required to make espresso coffee than conventional methods. Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the invention.

Brief Description of the Drawinσs

FIG. 1 is a illustration of part of an espresso machine showing the filter and coffee collection cup.

FIG. 2 is a flow chart of the improved espresso coffee extraction process.

Detailed Description of the Invention

Referring now to the drawings, there is shown in FIG. 1 a partial view of an espresso coffee machine 10 showing the handle assembly 12, the pressure regulation valve mechanism 16, the ground coffee bean filter 14 of the handle assembly 12, the outflow spout 18 from the filter and the cups 20 in which the espresso coffee is collected upon extraction.

FIG. 2 is a flow chart of the steps in the process of extracting espresso coffee which includes the improved process. In the following discussion reference will be made to both figures.

At step 100 coffee beans are ground. The grind that can be accommodated in the improved process includes a ranges from grind sizes finer than conventional espresso coffee grinds to the grind sizes coarser than conventional espresso coffee grinds.

At step 101 a measured volume of the ground coffee beans is placed in the filter 14 of the filter 12. Unlike conventional espresso extraction processes, the ground coffee does not need to be compacted in the filter 14.

At step 102 a measured quantity of water is moved through the ground coffee beans in the filter 14. Water pressure builds within the filter until a particular pressure level is reached. The particular pressure level is based on the optimum extraction pressure for a given volume and temperature of water.

When the optimum pressure is reached a valve mechanism 16 on the outflow spout 18 of the filter opens

(step 103) allowing the extracted espresso coffee to exit the filter. Any commercially available pressure regulating valve can be used, such as a Speedaire Model No. 2X947A, Dayton Electric Manufacturing Co., Chicago, IL 66648. The outflow spout 18 is downstream of the ground coffee beans. At step 104 the extracted espresso coffee is collected in a cup 20. In the improved process of extraction, extraction pressure is controlled by the valve mechanism 16 and not by a variable such as the degree of compaction of the ground coffee beans as in a conventional process.

Claims

1. An improved process for extracting espresso coffee from ground coffee beans comprising the steps of: placing ground coffee beans in a filter; moving water through said ground coffee beans in said filter; and controlling the pressure of said water surrounding said ground coffee beans between the inlet for said water and the downstream outlet for said water after said water has passed through said ground coffee beans so that the pressure differential thereacross remains constant regardless of variations in the inlet and outlet pressures.

2. Apparatus for extracting espresso coffee from ground coffee beans comprising: a source of pressurized liquid; a pressure regulating valve having an inlet for receiving said liquid and an outlet for discharging said liquid, said valve remaining closed to liquid flow therethrough until a predetermined pressure is reached between said inlet and said outlet and thereafter opening to allow flow of said liquid therethrough for maintaining a constant pressure between said inlet and said outlet; and means for receiving a container having said ground coffee beans and a filter for establishing a closed path for flow of said liquid from said source through said beans and said filter into said valve inlet.