NO162262B - PROCEDURE FOR PREPARING COFFEE EXTRACTS. - Google Patents

Abstract

1. Process for the preparation of coffee extract characterized by the following process steps : (a) short-time roasting of the coffee beans (b) breaking of the coffee beans (c) formation of an aroma distillate by means of steam distillation (d) formation of an aqueous primary extract (e) formation of an aqueous secondary extract (f) treatment of the secondary extract with a weakly basic ion exchanger (g) combining of the extracts obtained in (d) and (f) (h) concentration of the combined extracts (i) combining of the concentrate with the aroma distillate obtained in (c).

Description

The present invention relates to a method for producing coffee extract..;

Different methods are known for producing instant coffee. Usually, the coffee beans to be extracted are roasted, ground or crushed and extracted, after which the obtained extract is concentrated and dried.

During the extraction, it is possible to carry out different aqueous extraction steps. Thus, e.g. when extracting crushed roasted coffee, a primary extract is first prepared in a percolator with hot water, which has a particularly high proportion of aroma substances that are typical for roasted coffee. The extracted coffee beans can then be treated with process water in one or more further extraction steps to obtain a so-called secondary extract.

With known extraction methods for extracting coffee extract, the taste is often unsatisfactory. In order to achieve an improvement in this respect, various methods have been developed to free extracts or sub-extracts from taste-unfavorable substances. ;

It is also previously known to extract aroma fractions by steam distillation. After extraction of the roasted coffee, the aroma substances thus obtained are usually added back to the extract in order to achieve an improvement in the aroma.

The task underlying the invention is

to provide a method for producing coffee extract, by means of which products with improved taste properties can be provided in an economically advantageous manner.

According to the invention, this task is solved by a method which is characterized by steps a) to i) which are stated in claim 1.

The treatment of the secondary extract with ion exchangers

of the weakly basic type leads to a surprisingly clear taste improvement for the coffee extract when used at the same time

of the secondary extract which has been treated in accordance with the invention. When using the ion exchanger, on the one hand, the extract's pH value is changed, namely raised. This results in an overall more favorable pH value for the coffee extract in connection with the primary extract and possibly the aroma substances extracted by prior steam distillation. Thereby, it is recognized that the secondary extract contains acids that have an adverse effect on the taste of the coffee extract ("undesirable acids"). In contrast, the primary extract contains acids that are beneficial for flavor formation ("fine acids"). A feature of the method according to the invention is consequently a palatably effective reduction of the unwanted acids in the secondary extract.

Moreover, the surprisingly favorable effect of the treatment of the secondary extract with (weakly basic) ion exchangers is obviously also due to the adsorption effect of the ion exchanger with regard to (unidentifiable) substances,

which likewise exerts an unfavorable effect on the flavor formation of the coffee extract. The interaction between raising the pH value and adsorption of taste-unfavorable substances leads to the surprising improvement in taste.

The result obtained with the help of the invention with regard to the taste improvement of extract coffee can also be increased by using roasted coffee beans that have been treated according to the method of short-term roasting. In the case of short-term roasting based on known methods or in known roasting machines with roasting times of preferably 1-3 min, the roasted coffee or roasted coffee is provided with a higher proportion of aromatic

and extractives. -Furthermore, the proportion of desired "fine acids" in terms of taste is higher than with "normally roasted" coffee.

In a preferred embodiment,

the roasted coffee beans are crushed in the usual way, especially with a grinding degree of 3.5 mm. grain size.

The crushed roasted coffee can now immediately be subjected to a subsequent hot water extraction. Prior to this extraction, aroma substances can be extracted from the roasted coffee in a known or suitable manner which, in order to be sparing, should not be subjected to extraction and concentration, but which are again added to the extract after completion of these process steps. The separation of aroma substances can take place in particular by steam distillation. Preferably, this steam distillation is carried out at such a pressure that the treatment temperature is below 100°C.

In an attached flow chart, the course of the preferred embodiment of the method is illustrated.

Steam distillation of the roasted coffee is carried out in a percolator E1. The distillate obtained by vacuum treatment and subsequent condensation is combined with the aqueous extracts according to their concentration.

The e.g. Roasted coffee treated according to the above method is extracted with hot water in a special extraction circuit (the percolators E2 .. Ei). This creates a so-called primary extract with a high proportion of aroma substances and "fine acids". Extraction takes place in a conventional solids extraction device which can be operated with water at elevated temperatures. Suitable is e.g. a percolator. The process water is heated, passed through the percolators E2 .. Ei, and the obtained primary extract (PE) is combined with a secondary extract (SE) prepared and treated in the manner described below before the concentration of the aqueous extracts. The primary extraction takes place at relatively low temperatures

up to approx. 130°C, preferably at approx. 100°C.

After extraction of the thus obtained aqueous primary extract, the roasted coffee remains in the extraction container and is subjected to secondary extraction in this container (the percolators En .. Ei+1). This also happens with water at temperatures between 130°C and 200°C, preferably at approx. 170°C.

As can be seen from the "flow diagram", the secondary extraction is advantageously carried out in such a way that several percolators En .. Ei+1 are connected one after the other and that the process water is led through. This enters the percolator Ei+1

with the roasted coffee previously subjected to primary extraction. The percolator E1 with the highest degree of

extraction is removed, emptied and prepared for a new extraction step, as soon as the subsequent percolator after performing the primary extraction takes the position of the percolator Ei+1. A maximum of secondary extract (SE) is thus extracted from the roasted coffee.

The secondary extract (SE;) is then passed over an ion exchanger IA of weak basic type. On the one hand, this causes an increase in the pH value of the secondary extract. The pH value for this can be in the range between 4 and 5, e.g. at 4.5, and with the help of the ion exchanger (IA) is raised to 6-7, especially to 6.5. Furthermore, with the help of the ion exchanger (IA), not yet identified substances are bound, which substances obviously have an unfavorable effect on the taste of the coffee extract. Due to the adsorption effect and the influence of the pH value of the secondary extract, a clear, surprising taste-wise improvement of the coffee extract is achieved.

The ion exchanger in the embodiment of a weakly basic anion exchanger, especially in the OH form, can be microporous or macroporous. Weakly basic polystyrene-based anion exchangers in powder form or as granules (small spheres) are particularly suitable. The ion exchanger is further preferably added with a proportion (e.g. 9%) of diphenylbenzene for cross-linking. The ion exchangers marketed under the designation "type II" from the company Merck as well as ion exchangers marketed under the designation "Lewatit MP 62" from the company Bayer AG have proven particularly advantageous.

The treatment of the secondary extract in the ion exchanger preferably takes place in chargers. The extract with a pH value of e.g. 4.5 is passed through the ion exchanger and collected in a container on the outlet side. Thereby, the pH value for the treated extract is measured continuously. This gradually decreases starting from a relatively high value. As soon as a pH value in the desired order of magnitude has been reached, e.g. 6.5, the processing is interrupted.

The treatment in the ion exchanger can also be carried out con-

in

tively. The amount of weakly basic ion exchanger, the flow rate or the contact or residence time for the extract in the ion exchanger as well as the temperature affect

The pH value of the treated solution. The aforementioned data must be selected so that the desired increase in the pH value of the secondary extract is achieved. The treatment temperature is approximately at or below room temperature. When the temperature is reduced, the reaction rate is indeed reduced, but the adsorption capacity of the ion exchanger is improved.

After going through a charge of the secondary extract through the ion exchanger or after going through several times, this is regenerated. For this purpose, the ion exchanger is first flushed with water. Treatment is then carried out with e.g. baking soda. In connection with this, a renewed flushing with water takes place. The preceding cleaning of the ion exchanger preferably takes place at an increased temperature of e.g. 40-80°C.

The secondary extract treated in the above sense,

a clear brown liquid is combined with the primary extract and concentrated, e.g. in ordinary vaporizers. Afterwards, the distillate, possibly initially obtained by vacuum extraction, is added to the concentrate. The total mixture can then be dried in the usual way, e.g. by normal spray drying or freeze drying.

The method explained above is - when including short-term voting - shown in the attached "block diagram". Steam distillation has also been used to separate aroma substances before the extraction method.

The coffee extract obtained in accordance with the method according to the invention includes a clear aroma improvement, even if the secondary extract is used. During the processing of the secondary extract, due to the economically favorable side of the method, it is ensured that a high yield of roasted coffee is achieved while avoiding taste disadvantages.

The following examples serve to explain the invention, whereby example 1 shows results using "normally" roasted green coffee and example 2 results based on short-time roasted green coffee.

Example 1

1. Raw coffee blend

2. Roasting (long-term roasting)

Probat batch votes

Color value 11

Voting time 11 min 55 s

Gas pressure 61 mbar

m Roka 5 kg Total quantity Roka 20 kg

3. Paint

Buhler-Miag painting chair (Technikum) Slit width at top 3.4 mm

bottom 2.4 mm Bulk density ps 308 g/l Grain size d^Q 3.1 mm

4. Vacuum stripping

5. Split-Up extraction

Pilot plant

Primary extract - Roka amount 1.9 kg

- process water temp. at inlet ~100°C - pressure -10 bar

- quantity 60 l/h

- outlet quantity 30 kg

- solids 1.31%

- dividend 20.7%

- pH 5.10

Secondary extract - Roka quantity 1.9 kg

- process water temp. at inlet 170°C -~170°C -pressure ~17 bar -quantity 60 l/h

- outlet quantity 29.5 kg

- solids 1.18%; - dividend 18.3% <;>

- pH 4.5

6. Separation

Westfalia separator

Flow rate —100 l/h

before separation - TS 1.17% (TS = dry substance)

- pH 4.58

after separation - TS 1.10%

- pH 4.5 9

TS loss ~6%

7. Ion exchange treatment

Pilot plant

Column volume = ion exchanger volume = 4 1 = 2 kg Ion exchanger "Merck type II", weakly basic anion exchanger

Process parameter: Temperature = room temperature Volume flow extraction 30 l/h Total quantity extraction 40 1 Specific load 7.5 l/h Extraction per 1 IA Extraction before treatment - pH 4.59 - TS 1.10% Extraction after treatment - pH 6.55 - TS 1.00% TS loss n/9% 8. Mixing of primary and secondary extract in the ratio equal to those of the extraction formed quantities.

9. Concentration

Centritherm

Parameter: Hot steam temp. 65°C

Evaporation pressure 75 mbar Evaporation temp. 38°C Supply quantity extraction 30 l/h pH 5.46

TS 20%

10. Grafting of the extract with vacuum SD Inoculation amount = 100%

pH 5.41

11. Freeze drying

Pilot plant G 06

Example 2

1. Råka ffe mixture

2. Voting

Jetzone batch voices Color value 11

Voting time 90 s

Temperature 308°C

Ap 11.3 mbar

m Smoke 400 g Total quantity Smoke 20 kg

3. Paint

Buhler-Miag easel (Technikum)

4. Vacuum stripping

5. Split-Up extraction

Pilot plant

Primary extract - Smoke quantity 1.87 kg

- Process water temp. at the entrance ^100°C -pressure -10 bar -volume 60 l/h (pumped through quantity) 6. Separation Westfalia separator Flow rate 100 l/h

7. Ion exchange treatment

Pilot plant

Column volume = ion exchanger volume = 4 1 <=> 2 kg Ion exchanger "Merck Type II", weakly basic anion exchanger

Process parameter: Temperature = room temp.

Volume flow extraction = 30-35 l/h Total quantity extraction = 40 1

Specific load = 7 '/. 9 l/h Extra. per 1 IA

TS loss 8%

8. Mixing of primary and secondary extract in the ratio corresponding to those for extracting no amounts formed.

9. Concentration

Centritherm

Parameter: Hot steam temp. 65°C

Evaporation pressure 75 mbar Evaporation temp. 38°C Additive quantity extraction 30 l/h pH 5.34

TS 27%

10. Grafting of the extract with vacuum SD

Inoculation amount = 100%

pH 5.29

11. Freeze drying

Pilot plant G 06

Claims (6)

1. Process for producing coffee extract, characterized by the following process steps: a) short-term roasting of the coffee beans, b) crushing of the coffee beans, c) formation of an aroma distillate by steam distillation, d) formation of an aqueous primary extract, e) formation of an aqueous secondary extract, f) treating the secondary extract with a weakly basic ion exchanger, g) combining the extracts formed in point d) and f), h) concentrating the combined extracts, i) combining the concentrate with the aromatic distillate formed in point c). 2. Method according to claim 1, characterized in that the formation of the aqueous primary extract is carried out at temperatures up to 130°C, preferably at 100°C. 3. Method according to claim 1 or 2, characterized in that the formation of the aqueous secondary extract is carried out at temperatures between 130c and 200°C, preferably at 170°C. 4. Method according to claim 1 as well as one or more of the other claims, characterized in that the formation of the aqueous primary extract and/or the aqueous secondary extract is carried out in several percolators according to the counter-flow principle. 5. Method according to claim 1 as well as one or more of the other claims, characterized in that when the secondary extract is treated with a weakly basic ion exchanger, both the pH value of the secondary extract is increased and also that the taste-affecting substances in the secondary extract are adsorbed by the ion exchanger. 6. Method according to claim 5 as well as one or more of the other claims, characterized in that the pH value for the secondary extract is raised to preferably between 6 and 7 during the treatment with a weakly basic ion exchanger.