A PROCESS TO PREPARE A LIQUID COFFEE CONCENTRATE WITH REDUCED ACRYLAMIDE CONTENT BY TREATMENT WITH A SELECTIVELY PERMEABLE MEMBRANE

Abstract

A process for producing a liquid coffee concentrate that has a reduced acrylamide content. The process involves contacting a low aromatic aqueous coffee extract with a selectively-permeable membrane to reduce the acrylamide content of the extract, prior to combining the treated extract with a high aromatic aqueous coffee extract. In particular, the process comprises the steps of: a) providing a low aromatic aqueous coffee extract having a first acrylamide content; b) providing a high aromatic aqueous coffee extract; c) contacting the low aromatic aqueous coffee extract with a selectively-permeable membrane to provide a low aromatic aqueous coffee extract having a second acrylamide content; and d) combining the low aromatic aqueous coffee extract having a second acrylamide content and the high aromatic aqueous coffee extract to provide a liquid coffee concentrate, wherein the second acrylamide content is lower than the first acrylamide content.

Claims

1. A process for producing a liquid coffee concentrate, the process comprising the steps of: a) providing a low aromatic aqueous coffee extract having a first acrylamide content; b) providing a high aromatic aqueous coffee extract; c) contacting the low aromatic aqueous coffee extract with a selectively-permeable membrane to provide a low aromatic aqueous coffee extract having a second acrylamide content; and d) combining the low aromatic aqueous coffee extract having a second acrylamide content and the high aromatic aqueous coffee extract to provide a liquid coffee concentrate, wherein the second acrylamide content is lower than the first acrylamide content.

2. The process of claim 1, wherein the process comprises subjecting roasted and ground coffee to an aroma recovery process to obtain: the high aromatic aqueous coffee extract; and (ii) dearomatised roasted and ground coffee.

3. The process of claim 2, wherein the aroma recovery process involves contacting the roasted and ground coffee with steam and obtaining the high aromatic aqueous coffee extract from the steam.

4. The process of claim 2, wherein the low aromatic aqueous coffee extract having a first acrylamide content is obtained by aqueous extraction of the dearomatised roasted and ground coffee, wherein the aqueous extraction is conducted at a temperature of above 140° C., preferably 140 to 230° C.

5. The process of claim 2, wherein the low aromatic aqueous coffee extract having a first acrylamide content is obtained by the aqueous extraction of dearomatised roasted and ground coffee, preferably wherein the aqueous extraction is conducted at a temperature of from 200 to 260° C.

6. The process of claim 2, wherein prior to obtaining the low aromatic aqueous coffee extract having a first acrylamide content by aqueous extraction of the dearomatised roasted and ground coffee, the dearomatised roasted and ground coffee is subjected to an initial aqueous extraction at a temperature of below 170° C., preferably between 100 and 170° C. to obtain a further aromatic aqueous coffee extract which is combined in step d) with the low aromatic aqueous coffee extract having a second acrylamide content and the high aromatic aqueous coffee extract to provide the liquid coffee concentrate.

7. The process according to claim 1, wherein contacting the low aromatic aqueous coffee extract with a selectively-permeable membrane simultaneously concentrates the coffee extract.

8. The process according to claim 1, wherein the process further comprises a step of concentrating the low aromatic aqueous coffee extract having a second acrylamide content.

9. The process according to claim 1, wherein contacting the low aromatic aqueous coffee extract with selectively-permeable membrane comprises filtering the low aromatic aqueous coffee extract through a selectively-permeable membrane by reverse osmosis or nanofiltration.

10. The process according to claim 9, wherein a pressure of up to 3000 kPa, or up to 4000 kPa, is applied to the membrane during filtration.

11. The process according to claim 1, wherein the selectively-permeable membrane is selective for acrylamide.

12. The process according to claim 1, wherein the selectively-permeable membrane is selective for organic acids.

13. The process according to claim 1, wherein the selectively-permeable membrane has a pore size of between 0.1 to 10 nm.

14. The process according to claim 1, wherein the selectively-permeable membrane has a molecular weight cut-off of 200 Da, preferably 100 Da.

15. The process according to claim 1, wherein the second acrylamide content is at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 99% or 100% lower than the first acrylamide content.

16. The process according to claim 1, further comprising a step of drying the liquid coffee concentrate, thereby producing a soluble coffee product.

17. A liquid coffee concentrate obtainable according to the process of claim 1.

18. The liquid coffee concentrate according to claim 17, having a reduced level of acrylamide of 2-50% wt in the final product.

19. Use of a selectively-permeable membrane for reducing the acrylamide content of an aqueous coffee concentrate, wherein the selectively-permeable membrane is selective for acrylamide.

20. Use of a selectively-permeable membrane for reducing the organic acid content of an aqueous coffee concentrate, wherein the selectively-permeable membrane is selective for organic acid.

21. A soluble coffee product obtainable according to the process of claim 16.

22. The soluble coffee product according to claim 21, having a reduced level of acrylamide of 2-50% wt in the final product.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0110] The invention will now be described further with reference to the following non-limiting figure.

[0111] FIG. 1 shows an exemplary flow-chart of the method steps described herein.

[0112] FIG. 2 shows Acrylamide content before and after treatment in tertiary extract.

[0113] FIG. 3 shows Acrylamide content before and after treatment in combined secondary and tertiary extract.

[0114] FIG. 4 shows the reduction in the content in key organic acids when secondary and tertiary extract was filtered using a nanofiltration membrane.

[0115] A first step involves the provision of raw green coffee beans 5. These may be any suitable coffee beans 5, such as Arabica or Robusta beans, or a mixture thereof. The coffee beans are subjected to a roasting step 10 using conventional roasting processes to achieve desirably roasted beans.

[0116] The roasted beans are subjected to a grinding step 15. Grinding is typically effected using a roller or burr-type grinder, with the end particle size and distribution being selected depending on the subsequent extractions steps. For example, percolation extraction systems tend to rely on an average particle size of about 2 microns, whereas slurry-based processing systems may favour a finer particle size, such as down to about 300 microns.

[0117] The roasted and ground coffee is then subjected to an aroma recovery step 20, such as for example involving passing steam through the roasted and ground coffee. The steam is recovered and condensed to provide a high aromatic extract 25. The high aromatic extract 25 is set aside for subsequent use, as described below, or may be used directly in a continuous process where all of the steps are being conducted in parallel. The roasted and ground coffee which has been subjected to the aroma recover step are dearomatised by the process.

[0118] The dearomatised roasted and ground coffee is then passed to a primary extraction step 30 wherein hot water is passed through the roasted and ground coffee under pressure, such that the water is at a temperature of from 100 to 170° C. This produces a primary extract 35 which has a good flavour profile (albeit a low yield) and low thermal production markers.

[0119] The roasted and ground coffee is then passed to a secondary extraction step 40 wherein hot water is passed through the roasted and ground coffee under pressure, such that the water is at a temperature of from 140 to 230° C. This produces a secondary extract 45 which has a reasonable flavour profile and a good yield, albeit with moderate levels of thermal production markers, including acrylamide.

[0120] The roasted and ground coffee following the secondary extraction step 40, so-called spent coffee, can be passed to a tertiary extraction step 50. This would typically be hotter and for longer than the secondary extraction step 40, in a temperature range of 200 to 260° C. The roasted and ground coffee following this step would be a waste product, optionally combusted for thermal energy. The tertiary extract 55 from this tertiary extraction step 50 shows an amount of acrylamide.

[0121] The process as described so far has provided four extracts (25, 35, 45, 55). The tertiary extract 55 which is a low aromatic extract and, if desired the secondary extract 45, are then treated with a selectively-permeable membrane in an acrylamide reduction step 60 to reduce the levels of acrylamide in the product. The high aromatic extract 25 and the primary extract 35 are not subjected to the acrylamide reduction step 60 in order to avoid a loss of volatile flavour components.

[0122] The process optionally involves a concentration step 65. This can be performed on any of the extracts (35, 45, 55) to increase the solids of the extract. The secondary and tertiary extracts can be concentrated before the acrylamide reduction step 60, if desired, to decrease the volume of extract to be treated.

[0123] The process involves a mixing step 70. This involves blending the high aromatic extract 25 with the other extracts (35, 45, 55). The extracts can be blended simultaneously or in turn. The mixing step 70 can be conducted before or after any optional concentration step 65.

[0124] The product of the mixing step 70 is a concentrated liquid coffee extract 75 suitable for reconstitution with hot water to form a coffee beverage. Alternatively, the concentrated liquid coffee extract 75 can be dried, such as by spray-drying or freeze-drying to produce an instant soluble coffee powder 80.

[0125] The invention will now be further understood with reference to the following non-limiting examples.

EXAMPLES

Example 1

[0126] FIG. 2 shows the reduction in acrylamide content when tertiary extract was filtered using two types of selective membranes. Both types of selective membranes achieve a reduction of at least 30% in acrylamide in tertiary coffee extract.

Example 2

[0127] FIG. 3 shows the reduction in acrylamide content when secondary and tertiary extract was filtered using a nanofiltration membrane. A reduction of at least 50% was achieved.

Example 3

[0128] FIG. 4 shows the reduction in the content in key organic acids when secondary and tertiary extract was filtered using a nanofiltration membrane. A reduction of 46% was achieved for Glycolic acid, 65% for acetic acid 72% for formic acid and 80% in the case of lactic acid. All these organic acids are considered relevant in the flavour perception of coffee.

[0129] It is noted that, from top to bottom with respect to the start of the lines, the first (highest) is acetic acid, the second is formic acid, the third is lactic acid and the fourth (lowest) is glycolic acid.

[0130] The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the invention in addition to those described herein will become apparent to those skilled in the art from the foregoing description and accompanying figures. Such modifications are intended to fall within the scope of the appended claims. Moreover, all aspects and embodiments of the invention described herein are considered to be broadly applicable and combinable with any and all other consistent embodiments, including those taken from other aspects of the invention (including in isolation) as appropriate.

[0131] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by the ordinary person skilled in the art to which the invention pertains.

[0132] Various publications and patent applications are cited herein, the disclosures of which are incorporated by reference in their entireties.