GB2069527A - Controlling carbohydrate content of beer - Google Patents

Abstract

A method of controlling the final carbohydrate content of the beer in a beer-making process comprises providing a mash of ground malt at a temperature sufficient to gelatinize the starch while retaining amylase activity, (e.g. 63-70 DEG C), cooling the mash to a temperature below 60 DEG C, adding pullulanase enzyme, holding the mash until a desired fermentable sugar level is reached, filtering the liquor, and boiling the resultant wort to inactivate the enzymes.

Description

SPECIFICATION Controlling carbohydrate content of beer This invention relates to beer making processes, and specifically to a step of controlling the final carbohydrate content of beer. It is predominantly though not exclusively concerned with a method of making low carbohydrate and low calorie beers. Low carbohydrate beers can be less fattening than ordinary beers, where this is accompanied by low calories, can be drunk by diabetics, and have achieved widespread commercial success in the U.S.A.

In the production of low carbohydrate beers it is common practice to use an amyloglucosidase enzyme during fermentation. In our experience a number of disadvantages occur when this enzyme is used. The enzyme degrades dextrins in brewers wort to glucose; the high concentrations of this monosaccharide can cause glucose inhibition which results in slow fermentation rates. The enzyme is not destroyed totally during pasteurisation and thus can lead to quality variations. Amyloclucosidase also effects carboxypeptides which contribute to the foam stability of beers. Lastly, beers produced in this way are typified by poor flavour characteristics, specifically astringency.

The present invention avoids these disadvantages by using, in place of amyloglucosidase enzyme in the fermentation step, pullulanase enzyme in the mashing step. Pullulanase attacks the branching points of dextrins by splitting a 1-6 bonds; together with - and amylase it degrades dextrins to fermentable sugars, mostly maltose and maltotriose. Thus the present invention has the following advantages over the conventional prior art:a) The starch hydrolysing enzymes are inactivated by boiling in the copper-kettle, and are not active in the beer during or after fermentation.

b) Fermentation is faster, because glucose inhibition of the yeast does not take place.

c) The beers have good foam stability because pullulanase does not attack the carboxypeptidases.

d) The beers have good flavour characteristics.

Thus the present invention provides, in a beer-making process, a method of controlling the final carbohydrate content of the beer, which method comprises providing a mash of ground malt at a temperature sufficient to gelatinize the starch while retaining amylase activity, cooling the mash to a temperature below 600C, adding pullulanase enzyme, holding the mash until a desired fermentable sugar level is reached, filtering the liquor, and boiling the resultant wort to inactivate the enzymes.

The initial mash must be raised to a temperature sufficient to gelatinize the starch in the malt. In most cases this is about 630C. It is preferred not to raise the temperature of the mash higher than is necessary to gelatinize the starch, for no significant advantages appear to accrue from the use of higher temperatures. Specifically, above about 700 C, inactivation of the amylase enzymes in the malt becomes a major and undesired factor. The mash may be maintained at this gelatinization temperature for a period of up to two hours or more in order to allow the amylase enzymes to attack the starch and start to degrade it to fermentable sugars.

After this step, the mash is cooled to a temperature below 600 C, preferably in the range 50 to 600C, particularly about 550C, and the pullulanase enzyme added. The temperature range of 50 to 600C is chosen to be optimum for pullulanase enzyme activity, while nevertheless permitting substantial amylase activity as well.

The amount of pullulanase enzyme added will generally be in the range 0.01% to 1.0% by weight on the weight of the ground malt in the initial mash. The optimum level of pullulanase enzyme depends on various other factors of the process, including incubation time, temperature, pH and level of fermentable sugar desired. It is possible to use one or more other enzymes together with the pullulanase, for example fungal amylase, malt amylase, dextrinase, obligosaccharase or carbohydrase to achieve a desired effect.

A convenient way of cooling the mash from the starch gelatinization temperature to the temperature at which the pullulanase is added, is to dilute the mash with additional treated water (brewers liquor). Thus for example, the original mash may be made up using three quarters of the intended total liquor, and the remaining quarter added to cool the mash after gelatinization. This thicker mash during the starch-degrading step is advantageous since amylases are more active than in thinner mixtures. It is preferred that the final mash have a liquor: grist ratio of from 2.7:1 to 5.0:1, particularly from 3.3:1 to 4.5:1. The desired optimum is 4.0:1. If the liquor to grist ratio is too low, it is difficult to raise the fermentable sugar level high enough.If the liquor to grist ratio is too high, then the problem of low fermentability remains and in addition the extra water requires the expenditure of extra energy without producing any significant compensating advantage.

The mash is maintained at a temperature in the range of 50 to 600C for long enough to achieve the desired fermentable sugar level. Generally this is acheived in less than six hours at 550C. The temperature of the liquor during and after filtration, and indeed up to and including the copper/kettle, should preferably be maintained at around 55"C to encourage continued pullulanase action. With the same object in mind, the pH of the wort in the copper/kettle should preferably be in the range 5.4 to 6.2, particularly 5.8 to 6.1. This is higher than is usual; it can be achieved by adding an appropriate quantity of alkali such as calcium hydroxide, either during boiling, or, more preferably, to the mash itself at dilution and cooling.

Mashing and enzyme action are continued until a desired fermentable sugar level has been reached. For low carbohydrate beers, the percent apparent fermentability should generally be at least 97, preferably at least 99, and optimamally at least 100. By using the method of this invention, an apparent fermentability of at least 100% can quite readily be reached.

The following examples illustrate the invention.

EXAMPLE 1 Ground malt (200 kg) was mashed with brewing liquor (540 I) in a mash mixer to give a mash temperature of 630C. After 30 minutes the mash temperature was dropped to 550C by the addition of cold brewing liquor (1801 approx.). When the mash was at 550C, 0.1 kg of a commercial pullulanase enzyme preparation was added. The mash was then held at 550C for 2 hours before being transferred to the lauter tun. During wort run-off the sparge temperature was controlled between 55"C and 600C to prevent the wort rising above 550C. The temperature in the copper/kettle was held at 550C also until all the worts were collected. The pH in the copper-kettle was 6.0.

The collected worts were then boiled to inactivate the hydrolytic enzymes. Fermentation was completed in 20% less time than would have been the case if amyloglucosidase had been added to the fermenting wort. The resulting beer had excellent flavour and good foam stability.

EXAMPLE2 Certain parameters of the process of Example 1 were varied in order to determine their effect on fermentability. The initial mash temperature was either 630C or 680C, and the liquor to grist ratio after dilution varied between 2.7:1 to 4.9:1. Results are set out in the following table: Final Mash Temperature Liquor/Grist Fermentability "C Ratio % 63 2.7 99.1 63 3.0 100.3 63 3.0 100.3 63 3.3 101.2 63 4.0 101.4 63 4.9 101.3 68 2.7 100.0 68 3.0 100.1 68 3.3 100.8 68 4.0 100.6 68 -4.9 99.8 The best results are obtained at a mash temperature of 630C and a liquor/grist ratio of 3.3:1 to 4.9:1.

EXAMPLE 3 Malt (5662 kg) was milled and mashed with brewing liquor to yield a mash having a liquor to grist ratio of 2.71/keg. The temperature at completion of mashing was 630C and the pH was 5.4. After standing for 30 minutes, 51 hectolitres of brewing liquor at 1 20C were added, and the temperature adjusted to 550 C. The liquor to grist ratio was now 3.551/keg.

2.9 kg of pullulanase in slurry form was added and the mash transferred to a mash convertor over 1 5 minutes. The rinse liquor further diluted the mash to a liquor to grist ratio of 3.7 I/kg at this stage.

The temperature was held at 550C in the convertor for 105 minutes. At this stage the mash was tested for starch, the test proving negative. The pH at this point was 5.5.

The mash was transferred to a lauter tun over 1 5 minutes. About 400 hectolitres of wort were run off including 220 hectolitres of sparge in 13 hours. The sparge temperature was 550C. The first runnings had a gravity of 52.50 and the last runnings 7.00. The gravity of the wort in the copper was 31.1 0 and the pH 5.6. Heating was not started until all the worts had been run off from the lauter tun. At this point, make-up liquor at 550C was added to increase the volume to 510 hectolitres.

The collected worts were then boiled to inactivate the hydrolytic enzymes. Fermentation was completed in 37 hours. The resulting beer had excellent flavour and good foam stability.

Fermentability would have been improved if the mash had been held at a pH of 6.0 during pullulanase action. However, this commercial scale example demonstrates that good beers can be obtained according to this invention even if the pullulanase does not operate under ideal conditions.

Claims (1)

1. CLAIM

   1. In a beer-making process, a method of controlling the final carbohydrate content of the beer, which method comprises providing a mash of ground malt at a temperature sufficient to gelatinize the starch while retaining amylase activity, cooling the mash to a temperature below 600 C, adding pullulanase enzyme, holding the mash until a desired fermentable sugar level is reached, filtering the liquor, and boiling the resultant wort to inactivate the enzymes.