GB2072218A

GB2072218A - Sorghum beer

Info

Publication number: GB2072218A
Application number: GB8108649A
Authority: GB
Original assignee: Council of Scientific and Industrial Research CSIR
Current assignee: Council of Scientific and Industrial Research CSIR
Priority date: 1980-03-20
Filing date: 1981-03-19
Publication date: 1981-09-30
Also published as: ZM2581A1; PT72676A; PT72676B; GB2072218B; MW1281A1

Abstract

A method of making sorghum beer by converting a suitable starch containing material via a fermentable sugar to alcohol includes the steps of interrupting the fermentation to give a sterile partially fermented wort and starting the fermentation again by adding a suitable brewers' yeast preparation to the party fermented beer either immediately or after a period of time. The method enables the beer to be transported in a sterile state, and extends the shelf-life of the product.

Description

SPECIFICATION Sorghum beer This invention relates to a method of making sorghum beer.

A serious problem associated with the quality of sorghum beer made in the conventional manner concerns its rather short useful shelf life.

Traditionally, sorghum beer is brewed in such a way that the hydrolysis of starch to fermentable sugars, started during the so-called conversion process stage, is allowed to proceed continually during fermentation. Since the beer is sold for consumption before the end of such fermentation, the commercially available beer accordingly is not biologically stable.

Furthermore, during the conventional brewing process, the freshly brewed non-sterile wort, or, alternatively, a wort reconstituted by the addition of water to a wort concentrate, is inoculated with a brewers' yeast preparation; allowed to ferment while being bulk transported, or, alternatively, retail packed; and distributed. The beer accordingly is sold to the consumer in a state of partial carbonation which is achieved naturally by the carbon dioxide produced during fermentation.

It is accordingly almost unavoidable that microorganisms, foreign to the product, such as bacteria, non-brewing (wild) yeasts and mould, are randomly present in the wort and the fermenting beer.

Depending on the effect which the nature and level of this undesirable microbial presence has on the biochemical composition of the wort, and on changes in outside conditions such as temperature, for example, such microbial infection will sooner or later grow in numbers and produce undesirable substances which will impair the flavour of the beer and render it unacceptable, thereby terminating its useful shelf life.

The inability to predict the limit of the shelf life in acceptable terms to the consumer accordingly is costly since deliveries to sales points have to be frequent and significant quantities of unsaleable beer are often returned to the breweries.

It is accordingly an object of this invention to provide a method of making sorghum beer with which the aforesaid problems may be overcome or at least minimised.

According to the invention a method of making sorghum beer in conventional manner by converting a suitable starch containing material via a fermentable sugar to alcohol includes the steps of interrupting the fermentation after it had proceeded for a period of time and starting the fermentation again by adding a suitable brewers' yeast preparation to the partly fermented beer either immediately or after a period of time.

As soon as the fermentation is interrupted, the partly fermented beer is biologically stable, i.e.

substantially all microbial and biochemical reactions are arrested and the microflora, including any brewers' yeast which was carried over from the earlier reaction, is inactivated.

Preferably the further fermentation is carried out while the beer is in an unvented container.

The final product will accordingly be stable and can hence be stored or transported in this form for a substantial period of time.

Alternatively, the period between the time when the fermentation is interrupted and the time when it is again started may be utilised for the transportation, storage, etc. of the partly fermented beer.

In this case the fermentation may then again be started in a vented container just prior to offering the product for sale to the consumer whereafter it will have a similar shelf life as the conventionally brewed beer.

It will be appreciated that in this latter instance the fermentation which is initiated in the partly fermented beer may be allowed to take place while the beer is being held in bulk fermentation vessels or bulk transporting or holding tanks.

It will further be appreciated that during the period of further fermentation the beer will again be partially carbonated by the carbon dioxide produced naturally during the further fermentation reaction and that an ethanol concentration, similar to that of conventional sorghum beer, may be reached.

Depending on the condition in which the beer is held during the period of further fermentation, the extension to shelf life will be shorter or longer but the beer when sold within the predictable limit of its shelf life, will substantially have all characteristics, including flavour, of the traditional beer brewed in the conventional manner.

It will be appreciated that in both of the aforesaid cases the useful shelf life of the beer is extended and can hence be predicted in practical terms.

The fermentation may be interrupted by means of any suitable known physical and/or chemical methods which will render the partly fermented beer sterile without significant loss of ethanol or unfavourable change in any quality component or characteristic, except possibly for loss of part of its carbon dioxide. Some of these methods are, for example, discussed on pages 291-300 of volume 74 (1968) of the Journal of the Institute of Brewing.

Preferably the interruption is effected by subjecting the partly fermented beer to a suitable heat treatment.

Such heat treatment may for example, be effected by maintaining the partly fermented beer at a temperature in the order of 700C for a suitable period of time.

Alternatively the heat treatment may be effected by passing the partly fermented beer through a suitable pasteurisation unit.

The fermentation may for example be interrupted when the ethanol and/or residual fermentable sugar concentration in the partly fermented beer has or have reached a preselected value.

Further according to the invention the brewers yeast preparation employed for starting the fermentation again comprises a pure culture.

Preferably the amount of yeast added is sufficient to give a concentration in the beer of approximately 2 x 1 08 viable yeast cells per litre of beer.

If required, one or more yeast nutrients and/or fermentable carbohydrates may also be added to the partly fermented beer when inoculating it with the brewers' yeast preparation.

The yeast nutrients may be provided by adding a quantity of sterile brewers' wort to the partly fermented beer.

Thus, for example, sterile wort may be added to give a final concentration in the order of 0.25% (m/v) of fermentable carbohydrate in the partly fermented beer.

The fermentable carbohydrate may be provided by adding sucrose to the partly fermented beer.

Where sucrose is utilised in the absence of any sterile wort the sucrose may be added in a concentration sufficient to give the required amount of carbon dioxide in the final product.

It will be appreciated that the method according to the invention provides a manner in which the problems encountered with the conventionally brewed sorghum beer may be overcome or at least minimised.

It will further be appreciated that also intended for inclusion within the scope of this invention is the partly fermented beer being the product of the interrupted method as well as the fully fermented beer being the product of the completed method according to the invention.

The invention will now be described further by the following examples: EXAMPLE 1 Sorghum beer, which was prepared in the conventional manner, and which had been fermenting for three days at 250C, was sterilized by heating it to a temperature in the order of 700C and maintaining it at this temperature for a suitable period of time.

A culture of brewers' yeast was added to the sterilized beer which contained virtually no residual fermentable carbohydrates. The yeast was added so as to give a concentration in the beer of approximately 2 x 108 viable yeast cells per litre of beer. The beer was placed in sterile containers with an air space of approximately 0,75% (v/v) of beer, and sealed. Fermentation was allowed to proceed at 21 0C. The build-up of pressure within the containers reached a maximum of 7 kPa over 7 days. Beers were sampled after storage at 21 OC for 7 weeks and were judged to be completely acceptable. No bacterial contamination was evident in the final product.

EXAMPLE 2 The procedure followed in example 1 was substantially repeated except that, in addition to the pure culture yeast, sterile wort was added to the sterile beer to give a final concentration of fermentable carbohydrate of approximately 0,25% (m/v). Fermentation was allowed to proceed at 210C.

Pressure build-up reached a maximum of 70 kPa after 7 days. Beers were sampled after storage at 21 C for 1 5 weeks and were judged to be completely acceptable. No bacterial contamination was evident.

EXAMPLE 3 The procedure followed was substantially as in example 2 except that sucrose was added, at a concentration of 0,2% (m/v), after sterilization in place of sterile wort. Fermentation was allowed to proceed at 21 0C. Pressure build-up reached a maximum of 40 kPa over 7 days. Beers were sampled after storage at 21 0C for 7 weeks and were found completely acceptable and with no bacterial contamination evident.

EXAMPLE 4 The procedure followed was as in example 3 except that the sucrose concentration was 0,25% (m/v). Maximum pressure obtained was 55 kPa over 7 days. Beers were judged to be completely acceptable and without bacterial contamination after storage for 7 weeks at 21 C.

EXAMPLE 5 The procedure followed was as in example 4 except that sucrose was added at a concentration of 0,3% (m/v). Maximum pressure obtained was 80 kPa over 7 days. Beers were judged to be completely acceptable and without bacterial contamination after storage for 7 weeks at 21 cm.

EXAMPLE 6 Partly fermented sterile beer made by the procedures of any of the aforegoing examples were held in the sterile state for a substantial period of time before the further fermentation was initiated. In one case the further fermentation was carried out in sealed off containers according to the precedures described in any of the aforegoing examples. The results obtained were substantially the same as those set out above. In another case again the further fermentation was allowed to proceed in vented containers. In this case the final product had a shelf life similar to that of conventionally brewed sorghum beer packed in vented containers.

It will be appreciated that there are many variations in detail possible with a method and product according to the invention without departing from the scope of the appended claim.

Claims

1. A method of making sorghum beer by converting a suitable starch containing material via a fermentable sugar to alcohol including the steps of interrupting the fermentation after it has proceeded for a period of time and starting the fermentation again by adding a suitable brewers' yeast preparation to the partly fermented beer either immediately or after a period of time.

2. The method of claim 1 wherein the fermentation is interrupted by means of any suitable known physical and/or chemical method which will render the partly fermented beer sterile without significant loss of ethanol or unfavourable change in any other quality component or characteristic, except possibly for loss of part of its carbon dioxide.

3. The method of any one of claims 1 or 2 wherein the fermentation is interrupted by subjecting the partly fermented beer to a suitable heat treatment.

4. The method of claim 3 wherein the heat treatment is effected by maintaining the partly fermented beer at a temperature in the order of 700C for a suitable period of time.

5. The method of claim 3 wherein the heat treatment is effected by passing the partly fermented beer through a suitable pasteurisation unit.

6. The method of any one of the preceding claims wherein the fermentation is interrupted when the ethanol and/or residual fermentable sugar concentration in the partly fermented beer have or has reached a predetermined value.

7. The method of any one of the preceding claims wherein the brewers' yeast preparation comprises a pure culture.

8. The method of any one of the preceding claims wherein the amount of yeast added is sufficient to give a concentration in the beer of approximately 2 x 108 viable yeast cells per litre of beer.

9. The method of any one of the claims 7 or 8 wherein one or more yeast nutrients and/or fermentable carbohydrates are also added to the partly fermented beer when inoculating it with the brewers' yeast preparation.

10. The method of claim 9 wherein the yeast nutrients are provided by adding a quantity of sterile brewers' wort to the partly fermented beer.

1 The method of claim 10 wherein the sterile wort is added to give a final concentration in the order of 0,25% (m/v) of fermentable carbohydrate in the partly fermented beer.

12. The method of any one of claims 9-11 wherein the fermentable carbohydrate is provided by adding sucrose to the partly fermented beer.

13. The method of any one of claims 9-12 wherein the sucrose is utilised in the absence of any sterile wort and is added in a concentration sufficient to give the required amount of carbon dioxide in the final product.

14. The method of any one of the preceding claims wherein the further fermentation is carried out while the beer is in an unvented container.

1 5. The method of any one of claims 1-13 wherein the further fermentation is carried out while the beer is in a vented container or while it is being held in a bulk fermentation vessel or bulk transporting or holding tank.

1 6. The method of claim 1 5 wherein the period between the time when the fermentation is interrupted and the time when it is again started is utilised for the transportation, storage, etc. of the partly fermented beer.

1 7. The method of any one of claims 15 or 16 wherein the fermentation is started again just prior to offering the product for sale.

18. A method of making a sorghum beer substantially as herein described and as illustrated in the examples.

19. A sorghum beer made according to the methods of any one of the preceding claims.

20. A sterile partly fermented sorghum beer made by interrupting the fermentation during the conversion of a suitable starch containing material via a fermentable sugar to alcohol after a period of time.

21. A method of making a sorghum beer by initiating further fermentation in a sterile partly fermented beer which had been obtained by interrupting the fermentation during the conversion of a suitable starch containing material via a fermentable sugar to alcohol after a period of time by adding a suitable brewers' yeast preparation to the partly fermented beer.

22. A sorghum beer made according to the method of claim 21.