IE47886B1

IE47886B1 - Coffee product and process

Info

Publication number: IE47886B1
Application number: IE2150/78A
Authority: IE
Original assignee: Gen Foods Ltd
Priority date: 1977-11-01
Filing date: 1978-10-27
Publication date: 1984-07-11
Also published as: AU523189B2; FI64042C; NO147897B; AU4102978A; SE447534B; NO147897C; FI64042B; DK148912C; FR2406956B1; FR2406956A1; IT7851687A0; IT1106099B; JPS5476866A; CA1110104A; FI783197A; DK483978A; SE7810872L; JPS6113775B2; IE782150L; DK148912B

Abstract

Coffee prod. consists of free-flowing agglomerates contg. soluble coffee particles and finely ground, roasted coffee. Finely ground, roasted coffee proportion is 2-20 (8-12) wt. % w.r.t. the 2 coffee components, and has a particle size such that 90 wt. % of the ground coffee can pass through a 75 (25) mu screen. Granular, soluble coffee obtd. yields min. sediment on preparing beverages.

Description

The invention relates to a coffee product and to the production of such product. More particularly the invention is concerned with the product of a process in which roasted coffee in very fine grind particle size form is formed with soluble coffee into co-agglomerated granules, hereinafter termed agglomerates.

There has been interest from time to time in the past in admixtures of soluble coffee with var ious percentages, usually less than 15% by weight, of finely ground roasted coffee. Such admixtures have the advantage that they incorporate aromatic and flavourful elements of roasted coffee not readily possible in the soluble coffee portion, cer15 tainly when prepared by a conventional spray dried method. Such admixtures have been commercially sold from time to time; but have been admixtures of soluble coffee powder and roasted and ground particles which, though homogeneously mixed, result in very poor flowability and poor ease of spooning out.

Furthermore, such products are composed of roast and ground particles which tend to settle out in a made up brew with milk and/or water and form an undesirable amount of sediment with a resultant consumer negative. Some amounts of sediment as with home-brewed 100% roasted and ground coffee is how5 ever acceptable to the consumer, in fact the in-cup turbidity of such products is desirable.

It has now been discovered that a pleasing and acceptable coffee product is obtained if soluble coffee and finely ground roasted coffee are combined into agglomerates, for example by known methods of agglomeration. It has been found that such a product is highly flowable and retains substantially all the original aromatic elements of the roasted ground coffee with an improvement in the flavour of the coffee product.

Accordingly, the present invention provides a coffee product consisting of free-flowing agglomerates comprising soluble coffee particles and finely ground roasted coffee, said finely ground roasted coffee being present in an amount of 2 to 20% by weight based on the weight of the two coffee constituents, and having a particle size such that 90% by weight of the ground coffee passes 75 micron mesh. Preferably the particle size of the finely ground coffee is less than 50 microns and more preferably 90% of the coffee passes a 25 micron mesh. It is most preferred that substantially all the coffee has a size between 5 and 20 microns.

Using finely ground roasted coffee having a particle size at the lower end of the sizes just specified produces minimal sedimentation when the agglomerates made from such coffee constituent are made into a beverage.

The dry grinding of roasted coffee beans to relatively coarse grinds is a well known operation in the coffee industry. Various workers have described the fine grinding of roasted coffee, while preserving its aromatic character, by employing a cryogenic grinding technique involving a single stage; in such a method the roasted coffee beans are pre-cooled before grinding to temperatures below 50°C, for example as described in United States Patent Specification No. 3,261,689. Alternatively, it has been proposed to feed liquid nitrogen into a grinding mill during the grinding of roasted coffee beans, as described in Food Engineering, May 1962, pages 62 and 63. Other methods of grinding roasted coffee beans are described in British Patent Specifications Nos. 1,424,264 and 1,476,854. These methods, however, still provide only relatively fine grinds and do not provide in general the most desired average particle sizes of down to 20 microns or less. It may be noted from United States Patent Specification No. 3,261,689 that only 50% of the ground coffee passed through a 200 U.S. mesh screen (i.e. 74 microns), and in British Patent Specification No. 1,476,854 tlie ground coffee was not finer than 70 mesh (210 microns). It will also be noted that the general procedure in the prior specifications is to suspend such ground products in liquid coffee extract, and then spray dry; this spray drying step inevitably leads to the loss of volatile components and also products are produced which have some flowability problems.

The previous proposals referred to above have not provided a sufficiently fine-size roasted coffee product and a method of producing such a product admixed with conventional soluble coffee in such a way as to give a flowable and flavourful product.

Desirably in practising the present invention, the fine-subdivision of roasted coffee beans is accomplished by a method of grinding which incorporates both pre-cooling of the roasted coffee beans to below 0°C, and preferably to below minus 45°C, coupled with the use of air classification of the finely ground roasted coffee employing cooled air in the classification step. The pre-cooling is preferably carried out with liquid nitrogen so that cooled gases in the classification stage include nitrogen and air in admixture. The fine-subdivision of the roasted coffee beans may be effected using an impact mill fitted with means for air classification which allows only ground coffee in the required particle size to leave as product from the mill. However, the air classification system may be external to the mill, with the provision for return of the coarser fraction to the mill. Other means for providing the required particle size of finely ground roasted coffee with acceptable minimal loss of volatile components may be used. Certain commercial types of high speed impact (or other mills), such as pin-disc mills, are available, which can achieve the required particle size without need for either external or internal classification. Although it is not preferred a grinding method without employing liquid refrigerant may be used to provide the finely ground roasted coffee.

In accordance with this invention the finely ground roasted coffee is formed into agglomerates with soluble coffee and the soluble coffee is preferably one having an average particle size of less then 50 microns. The two coffee constituents will be mixed to form a substantially homogeneous mixture and thereafter co-agglomerated to form the agglomerates of the invention. The agglomeration may be effected in a variety of ways but is preferably effected using the procedures described in our Patent Specification No. 32921, which specification also describes the pre-milling of the soluble coffee, which is a desirable step in this present invention.

The agglomerates of the present invention may contain from 5 to 20% by weight of the roasted and finely ground coffee and preferably from 8 to 12% by weight. If desired a proportion of the inherent coffee oil may be removed from the finely ground roasted coffee before the grinding step prior to the forming of the agglomerates of this in15 vention; techniques for effecting this are well known to those skilled in the art.

Preferably the agglomerates of the coffee product of this invention have an average particle size greater than 850 microns and more preferably between 1200 and 2400 microns.

EXAMPLE 1 kg. of a roasted coffee blend (Columbians/Santos) were immersed in liquid nitrogen for a short period and then passed through an impact hammer mill filled with an internal air classifier. The grinding was carried out with liquid nitrogen introduced to both the milling chamber and to the classifying air stream. The emergent air temperature was noted to be -45°C. The use of the liquid nitrogen assisted in the fine grinding of the coffee as it had an embrittling effect on the coffee. Particle size measurements of the ground product were made by means of a Coulter (Trade Mark) Counter. 98% of the product by weight had a particle size diameter of less then 32 microns, and 91% by weight had a particle size diameter less then 25 microns. 80% of the product by weight was between 5 and 25 microns particle size. kg. of the resultant finely ground coffee was then mixed with 162 kg. of a soluble coffee powder which had been prepared in a conventional manner in an extraction battery from roasted coffee and by spray drying using temperatures of 2Z0°C (inlet) and 100°C (outlet).

The mixture of ground and soluble coffee was fed through a Bauermeister mill, when the particle size of the constituent spray dried powder was reduced to less than 50 micron size. The mixture of fine powders was then agglomerated into granules in the manner described in our Patent Specification No. 32921. The course agglomerates were cooled and screened to give the final product of required particle size. The under size material was recycled as also described. 65% of the finished agglomerated product had granule sizes greater than 850 microns, whilst 50% had granule sizes between 1200 and 2400 microns, by weight.

The product on make up with hot water, was compared as a 5 beverage with the same spray-dried soluble coffee alone. It showed increased aromatic impact with improved flavour and in-cup appearance (turbidity). The granules were also highly flowable and easily spooned out.

EXAMPLE 2 18 kg. of a roasted coffee blend (Columbians/Santos) were passed through a high speed impact pin-disc mill with contra-rotating discs. Liquid nitrogen was introduced at two points in the screw system feeding the mill and the temperature in the milling chamber was recorded as -50°C. More than 99% of the product by weight had a particle size of less than 63 microns and 97% by weight was less than 40 microns particle size. The average particle size was found to be between 10 and 20 microns. Particle size measurements were made by conventional sieve analysis, using also air-jet clearance attachment in the sieves used.

The resultant finely ground coffee was mixed with soluble coffee, and a free-flowing agglomerate prepared in the same way as the first example. The made-up product also showed improved aromatic impact and in-cup appearance.

Claims

1. A coffee product consisting of freeflowing agglomerates comprising soluble coffee particles and finely ground roasted coffee, said finely ground roasted coffee being present in an amount of 2 to 20% by weight based on the weight of the two coffee constituents and having a particle size such that 90% by weight of the ground coffee passes a 75 micron mesh.

2. A coffee product as claimed in Claim 1, wherein the finely ground roasted coffee has a particle size of less than 50 microns.

3. A coffee product as claimed in Claim 2, wherein the finely ground roasted coffee has a particle size such that 90% by weight of the ground coffee passes a 25 micron mesh.

4. A coffee product as claimed in Claim 3, wherein the finely ground roasted coffee has a particle size such that substantially all the coffee has a size between 5 and 20 microns.

5. A coffee product as claimed in any one of the preceding claims wherein roasted coffee beans were finely ground in a manner such that the aromatic character of the coffee was preserved.

6. A coffee product as claimed in Claim 5, wherein the roasted coffee beans were pre-cooled before grinding to a temperature below minus 45°C.

7. A coffee product as claimed in any one of the preceding claims, wherein the finely ground roasted coffee having the desired particle size was selected by means of an air classification step.

8. A coffee product as claimed in any one of Claims 1 to 6, wherein the finely ground roasted coffee was prepared by use of an impact mill fitted with means for air classification which allows only ground coffee having the required particle size to leave product from the mi 11. on$

9. A coffee product as claimed in any/of the preceding claims, wherein the agglomerates comprising soluble coffee particles and finely ground roasted coffee were formed by a process including the steps of dropping a powder in the form of a continuous vertical curtain and directing upper and lower jets of steam at a substantial angle onto one side of the said vertically moving curtain of powder at a steam pressure sufficient to form wet agglomerates and displace the said falling material laterally from the said curtain into a drying zone, the angle of the said upper jet of steam being sufficient to disrupt the said curtain into wet agglomerates of varying size, density and moisture content and the angle of the said lower jet of steam being sufficient further to wet and displace the said wet agglomerates, the force of the lower jet being sufficient to render the size, density and moisture content of the said agglomerates more uniform.

10. A coffee product as claimed in any one of the preceding claims, wherein the agglomerates contain from 8 to 12 per cent by weight of the finely ground roasted coffee.

11. A coffee product as claimed in any one of the preceding claims, wherein at least 65% by weight of the agglomerates have an average particle size greater than 850 microns.

12. A coffee product as claimed in Claim 11, wherein the agglomerates have an average particle size greater than 850 microns.

13. A coffee product as claimed in Claim 12, wherein the average - 10 47886 particle size of the agglomerates is between 1200 and 2400 microns.

14. A coffee product as claimed in Claim 1 and substantially as hereinbefore described in either of the Examples.