DE2729961B2 - Process for accelerated fermentation of a lager beer by under-fermentation at elevated temperatures - Google Patents

Description

The invention relates to a method for accelerated fermentation of a lager-type beer through sub-fermentation at elevated temperatures and the use of excess carbon dioxide pressure.

There are two methods of fermenting malt beverages. For the production of beers of the ale type, a top fermentation process is used in which types of yeast are used which rise to the surface of the fermentation wort. The temperature of the top fermentation is usually set to about 15 to 20 ° C during the most active time of the fermentation. For the production of a beer of the lager type, a lower fermentation process is used in which a type of yeast is used which remains more or less uniformly suspended in the entire fermentation wort _{during the active fermentation due to the natural movement caused by rising CO 2 bubbles;} it then settles into a more or less compact layer on the bottom of the fermentation vessel when the fermentation is over. The lower fermentation temperature is expediently set to around 10 to 15 ° C. during active fermentation.

It is known that the fermentation is accelerated during the bottom fermentation by increasing the temperature and the fermentation time can be shortened significantly. Unfortunately, the beer obtained in this way has one undesirable wine-like odor, which is atypical for a lager beer. The literature leads this Wine-like odor is due to increased amounts of volatile components in lager beer, which variously are called fusel alcohols and esters.

Violent extraneous movement, ie an additional movement to the natural movement occurring in commercially available fermentation tanks, which occurs as a result of the normal production of CO ₂ by the fermentation yeast, can, as is known, significantly reduce the fermentation time of the lager beer. However, this measure has an adverse effect on the smell of beer, which, as at higher temperatures, is due to the increased content of volatile compounds such as fusel alcohols.

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<> o The use of higher temperatures or additional stirring during the bottom fermentation leads to very strong yeast growth. Thus, although the technical measures mentioned above shorten the fermentation time, they also have the disadvantages that the yeast grows extremely rapidly and volatile products are more likely to be formed. Both affect the smell of the l-ager beer.

In J. De Clerck, "Supplements to the brewery's textbook", 2nd edition, 1964-1965, Heft II, p. 65, 1970, is accelerated fermentation at 20 ° C under increasing counter pressure up to a maximum of 2 atm various yeast strains reported this process leads to an increased formation of higher alcohols of 70 mg / 1 versus 60 mg / 1. Before starting by "letting it on" at a higher temperature warned, however, because the content of higher alcohols then rises by leaps and bounds, about 15% Increasing the content of fusel oils is no longer acceptable for the quality of a lager beer.

The invention is based on the object of a method for accelerated fermentation of a lager beer to indicate in the case of elevated temperatures and excess CO2 pressures, despite the acceleration caused by the temperature fermentation time does not lead to increased yeast growth and increased formation of Fusel alcohol leads, but delivers a perfect-tasting lager beer. The procedure should be like this be stated that it is with respect to the yeast growth of a lager beer fermentation under normal conditions corresponds, although higher temperatures are used, and a lager beer without the undesirable produces a wine-like odor.

The method specified in claim 1 is used to solve this problem; preferred configurations this method forms the subject of subclaims 2 to 4.

During the active phase of conventional lager fermentation, the entire fermentation liquid is known to be oversaturated _{with CO 2.} Vigorous exogenous movement reduces this CO ₂ oversaturation. According to the invention it has been shown that this supersaturation remains relatively constant during the active fermentation phase and does not change during the transition from conventional lager fermentation to fermentation at a higher temperature. The degree of supersaturation is independent constant in the precisely investigated range of 13.9 ° -22.2 ⁰ C and 0-1.1 atmospheres gauge back pressure and thus both the temperature as well as from COrGegendruck.

It has also been found that it is the concentration of dissolved CO ₂ in the fermentation liquor that determines the extent to which yeast growth is suppressed. By maintaining the concentration of dissolved CO ₂ at a level that corresponds to that of normal fermentation of a lager beer, the yeast growth is therefore adjusted according to the invention to a desired level when using higher temperatures within the range specified in the claims. Nevertheless, a lager beer is obtained that does not have an undesirable wine-like odor. To adjust the concentration of the dissolved CO ₂ to a certain level, CO ₂ overpressure is used. It has been shown that the concentration of the dissolved CO2 is ^{adjusted to 1.5 to 2.0 cnv per cm 3 of} fermentation liquid and that a carbon dioxide overpressure of 0.14 to 1.4 atmospheres is used for this purpose

must be kept at a temperature in the range of 15.5 to 29.5 ° C to complete fermentation in 50-175 hours.

It is essential that the specified concentration is maintained of dissolved CO ₂ in the fermentation liquor during the entire active leavening phase of 50-175 hours, the other hand would hold the one COrGegendruck at 20 ⁰ C to 2 atm, a higher concentration of dissolved CO ₂ would be set and a considerable suppression of yeast growth, namely 2 to 3 times, is achieved, while in the conventional unaccelerated fermentation process at low temperature a yeast increase to 4.5 times the set value takes place

According to the invention, temperatures of 15.5 ° C. to 23.9 ° C. are preferably used in conjunction COr overpressures of 0.14 to 0.84 atmospheres, whereby the The concentration of dissolved CO2 is kept at the desired level and the fermentation is already in about 100 Sbuiden is completed.

In order to maintain the desired level of dissolved CO2, it is necessary to use an increased excess pressure of carbon dioxide under the conditions of a temperature increase, the excess pressure being selected so that the level of dissolved CO2 again falls to 1.5 to 2.0 cm ³ per cm ^{3 of} fermentation liquid is set.

During the active fermentation phase, the concentration of dissolved CO ₂ is dependent on the CC> 2 excess pressure and the fermentation temperature, i.e. inversely proportional to the temperature and directly proportional to the pressure, jo Because of the supersaturation present, the proportionality is greater than in the case of saturation, for the latter the values are taken from the literature. With a movement of the fermentation liquid that approaches the Ji movement caused by the natural CC> 2 formation, the concentration of dissolved CO ₂ during fermentation corresponds to 1.5 times the dissolved CO 2 at saturation within the entire temperature range.

By dividing the desired concentration value w for the dissolved CO2 during fermentation under these conditions of stirring by 1.5, the saturation level of the dissolved CO2 can be determined. With the two details of the fermentation temperature and the saturation level of the dissolved CO2, the «required CO2 overpressure, z. B. obtained from references. Since the effect of the amount of movement is known in the supersaturation, these conditions of temperature and CO2 overpressure in turn lead to the desired CO ₂ level.

Through the quantitative relationship found between the fermentation parameters temperature and CO2 overpressure and its influence on the degree of CO2 supersaturation during the active phase of the Storage fermentation makes it possible for the process according to the invention to increase the respective CO2 overpressure Calculate with which the concentration of dissolved CO2 at the respective temperature to the specified The range can be adjusted to reduce the formation of fuse alcohol during fermentation at higher temperatures control and keep it at the level of normal lager fermentation, with the result that despite the Shortening the fermentation time to z. B. 100 hours a beer of the same quality is obtained.

There is a direct linear relationship between the external stirring and the degree of h> CO ₂ supersaturation, so that with constant movement (stirring speed) by setting a certain CO ₂ overpressure at a given temperature, a precisely determined level of dissolved CO2 can be set .

The effect of changing one of the three fermentation parameters COi excess pressure, temperature and movement on the concentration of dissolved CO2 as it prevails during fermentation can be precisely predicted. Insofar as it is for example desirable to reduce the fermentation time by the application of additional movement, it is possible to predict the effect of the motion on the over-saturation and to provide the necessary CO2 overpressure required to reduce the concentration of dissolved CO ₂ during fermentation to a level which normally occurs in a conventional lager fermentation

F i g. 1 shows in the diagram the dependence of the degree of supersaturation on the stirring speed

F i g. 2 shows from the evaluation of experimental data that between the concentration dissolved CO2 in the fermentation liquid (abscissa) and the yeast growth (right ordinate) or the content of formed volatile constituents (left ordinate) there is a linear relationship, so that by suitable Adjustment of the CO2 concentration in the fermentation liquid both responsible for the beer quality Parameters can be set as required.

_{The CO 2} overpressure is expediently applied at the end of the yeast delay phase. In addition and / or alternately, the CO 2 overpressure can partly be the normal and autogenously developed pressure during the fermentation process. This natural pressure is retained in the vessel and in the upper space, but can also be released continuously or from time to time, with the desired overpressure being maintained.

The temperatures for the conventional fermentation of beer from the lager type in the United States are usually in the range of 12.2 to 13.9 ° C. It has been shown that when this temperature is used, an increase in the C0 ₂ concentration or the use of a CO ₂ overpressure does not reduce the fermentation time. According to the invention, temperatures of at least 15.5 ° C. are recommended. Temperatures up to 29.5 ° C can be used. The upper temperature limit is the temperature at which the yeast metabolic process changes significantly. Depending on the conditions, this temperature is 29.5 ° C.

These higher temperatures must be accompanied by _{excess CO 2} pressures in order to keep the concentration of the dissolved CO2 at the desired level of 1.5 to 2.0 cm ³ per cm ^{3 of} beer. Otherwise the beer will have a wine-like and / or ester-like taste and smell.

The fermentation process is an exothermic process and the fermentation liquid heats up. With conventional Fermentations remove this heat by cooling. In the present invention cooling is also however, it is only desirable for the purpose of keeping the fermentation wort at a temperature within the higher To maintain the temperature range. That is, not so much in the process of the present invention Heat is withdrawn, as with traditional fermentation processes. On the other hand, external heat can be invested when circumstances so require.

According to the invention, by maintaining the concentration of the dissolved CO ₂ at a certain level with the aid of the CO 2 overpressure, a clear one becomes

Time savings achieved. Fermentation, which normally takes about 8 days to complete, can by using the invention, the fermentation time can be reduced to 4 to 5 days. On the other hand, the The time for fermentation, which usually lasts 10 days, can be reduced to 5 to 6 days. Generally leads the invention to a reduction in fermentation time under a series of conditions by about 25 to 75%. Fermentation is usually completed within 50 to 175 hours. This time saving leads ι ο to the fact that the capacity of the device is increased by the aforementioned percentage factor can be.

A number of fermentations were carried out to confirm the usefulness and effectiveness of the invention demonstrate. The fermentation vessel used in the investigations was a 130 liter vessel stainless steel with a working cap; ity of 100 liters, cylindrical, about 83.8 cm high and with an inside diameter of 43.2 cm. It was equipped in a conventional manner; H. with a Pressure cap, temperature and pressure valves, lines for steam inlet and outlet and one Drain cock for the liquid at the bottom. The jar came with an outer cooling / heating jacket and provided with a turbine-type stirrer and baffles. This arrangement made an accurate one possible Control of movement, temperature and pressure in the upper space over a wide range.

The concentration of the volatile components of the fermented beer was by conventional gas chromatography 'techniques was either the head space gas above an enclosed sample (see FIG. "Gas-liquid chromatography (GLG) Tests", infra) analyzed or a Schwefelkoh- s => lenstoff extract of the beer was analyzed The yeast concentration was determined by counting cells with a counting chamber and also determined by determining the dry weight of the centrifuged yeast. and the disappearance of fermentable sugars as determined by high pressure liquid chromatography.

A series of fermentations were carried out in Examples 1 to 7 in the 100 liter fermentation vessel described above using a conventional commercial wort, d. h, a 14.1 plato wort which is produced using a Ratio of 55/45 addition of malt was shown, with the addition of 65% being commercially available Cereal grains and 35% commercial brewer's syrup.

The conventional commercial wort was saturated with CO2 and turned on with lager yeast in the production equipment according to the usual procedure germ-free from a fermentation tank filled with CO2 into a 100-1 fermentation tank 20 hours after switching on Transferred This ensured that the process steps before fermentation did not deviate from conventional commercial practice. The 20 hour Staying in the commercially available fermentation vat before transfer roughly corresponds to the delay phase the yeast during which the yeast grows little but the oxygen which during the aeration added, is absorbed in preparation for growth. Without this delay in the transfer, the CÜ2 imprint would have been in the 100 liter fermentation tank must be delayed to ensure oxygen absorption.

The agitation was kept at 33 revolutions / min in the 0.61 m deep 100 liter fermentation tank since It was found that this mixing speed sets the agitation conditions, which usually as a result of the CXV evolution by the yeast during fermentation at the 6 foot depths commercially available fermentation tanks.

Fermentation was considered to have ended when both carbohydrate assimilation ceased (at an acceptably low residual level) and the diacetyl concentration to a value of 0.10 ppm sank. These two conditions are the traditional criteria for the final termination of the Lager fermentation.

After fermentation was finished, the beer became raw withdrawn, clarified, filled into bottles and analyzed as described in the literature. The following examples illustrate the invention.

example 1

This example is a control example. The conventional fermentation conditions are used. These conditions result in a decent raw beer. It is noteworthy that a total time of 196 hours was required to complete the fermentation.

100 liters of the conventional wort, which was aerated and pitched at about 10 million yeast cells / cm ³ , were fermented at a constant temperature of 13.9 ° C using low stirring speed (33 revolutions / min) and without excess pressure. The yeast concentration reached a maximum of 5.77 g / L (dry weight basis) and 60 million cells / cm ³ . It took 160 hours to ferment the available carbohydrates and an additional 36 hours (approximately) to reduce the dicacetyl level to 0.10 ppm. The concentration of volatile substances was expressed as the total area of the compound peaks from gas-liquid chromatography (GLC) relative to the peak region of an internal standard, which was taken to be 100. In this way, the concentration of the volatile components was determined to be 904 (by analyzing the CS2 extract of the beer) and 648 (by analyzing the steam above the beer).

Example 2

This example is another control example. It corresponds to example 1, with the Exception that the temperature increases to 22 ^ ° C was to determine whether the elevated temperature would shorten the fermentation time while at the same time acceptable product was obtained. It turns out that the time decreased, but an unacceptable one Product was obtained.

100 liters of the conventional wort were aerated and made with about 10 million yeast cells / cm ^3. They were fermented at a constant temperature of 22 ^ ° C using a low stirring speed (33 revolutions / min) and without excess pressure.The maximum yeast concentration reached 6.03 g / l (dry weight basis) and 69 million

nen yeast cells / cm ³ . It took approximately 90 hours to decrease the diacetyl level to 0.10 ppm and an additional 10 hours to complete the fermentation of the available carbohydrates. This results in a total time of 100 hours. The volatile content as the total relative GLC peak area was 956 (CS ₂ extract) and 752 (upper space) compared to the internal standard, which was set equal to 100. The information in the table shows that the high temperature in Example 2 reduced the fermentation rate, but increased the volatile matter content relative to Example 1 .

Example 3 Example 4

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and employed with about 10 million yeast cells / cm ³ and fermented at a constant temperature of 22.2 ° C, a stirring speed of 33 revolutions / min and a CO ₂ overpressure of 1.05 atm. The yeast concentration reached a maximum of 5.37 g / l (dry weight basis) and 53 million cells / cm ³ . It took 90 hours to assimilate all fermentable sugars and an additional 5 hours (for a total of 95 hours) to reduce the diacetyl level to 0.10 ppm. The content of volatile substances as the total relative GLC peak area was 820 (CSr extract) and 298 (upper space) Example 3 shows that in the presence of a CCV overpressure of 1.05 atmospheres the formation of volatile substances, as is normally the case with fermentation at this temperature The concentration of dissolved CO2 was 2 cm ³ / cm ³ beer.

35

This example is another control example and the conditions of this fermentation ' were chosen to take the characteristics of conventional commercial lager fermentation and the characteristics of the to demonstrate raw beer obtained.

100 liters of the commercial wort described above were treated in the manner also described above and then fermented at 15 ° C without using a CO overpressure. A constant low agitation speed of 33 revolutions per minute was used in order to establish the natural agitation conditions in the commercial fermentation tank. The concentration of dissolved CO ₂ in the fermentation liquid was 1.52 cm ³ of CO ₂ / cm ^{3 of} liquid

It took about 172 hours to decrease the diacetyl level to 0.10 ppm and an additional 6 hours It took hours for the accessible carbohydrates to ferment. So became one Total time of 178 hours (7.4 days) required to finish the fermentation after mentioned above To achieve criteria.

The yeast concentration reached a maximum of & o 53 g / l (dry weight basis) and 58 million cells / cm ³ . The total concentration of volatile products was determined by gas-liquid chromatography to be 872 relative to the reference standard as used in this analytical method

The fermentation time required and the yeast growth and the Volatile concentrations are typical of the lager of the invention.

Example 5

The conditions of this fermentation were chosen in such a way that the influence of the fermentation process in a To demonstrate temperature well above normal camp practice.

100 liters of the above-mentioned commercial wort were treated, as also stated above, and then fermented at 22.2 ° C. without the use of excess CO2. A constant stirring speed of 33 revolutions / min was used in order to set the agitation conditions which occur naturally in commercially available fermentation tanks. The concentration of dissolved CO2 in the fermentation liquid was 1.30 cm ³

It took about 85 hours to ferment the available carbohydrates and another 4 hours to bring the diacetyl levels down to 0.10 ppm. The total fermentation time according to the characteristics mentioned above was 89 hours.

Yeast growth reached a maximum of 6.45 g / l dry weight and 77 million cells / cm ³ . The total volatile concentration relative to the GLC reference standard was 950.

Thus, while the increased fermentation temperature shortened the fermentation time by about 50%, that was Yeast growth and volatile matter concentration increased to a level which is significantly higher than our raw lager.

Example 6

The conditions of this fermentation embrace the invention. The conditions are chosen so that in the application of the correct CO2 overpressure the concentration can be maintained of dissolved CO ₂ and the fermentation can be carried out at a temperature which is far above the accepted stock fermentation practice is without the usual adverse effects of the excessive yeast growth and the excessive formation of volatiles of high temperature fermentation occur, while on the other hand a shortened fermentation time is obtained due to the elevated temperature.

100 liters of the above-mentioned commercial wort were treated as also mentioned above and subsequently _{fermented at a constant temperature of 22 ° C. and a constant CO 2} overpressure of 0.56 atmospheres. A constant stirring speed of 33 revolutions / min was selected around the Movement conditions, as they occur naturally through the CO development in commercial fermentation tanks, to be set. The concentration of dissolved CO ₂ in the liquid was 1.88 cm ³ of CO ₂ / cm ^{3 of} the fermentation liquid

It took about 93 hours to decrease the diacetyl level to 0.10 ppm and another 2 hours It took hours to complete the fermentation of the accessible carbohydrates. Thus became a total time of 95 hours (4.0 days) is required to reach the end of fermentation based on the features described above.

Yeast growth reached a maximum of 53 g / l dry weight and 59 million cells / cm ³ . The total volatile concentration relative to the GLC reference standard was 820.

Thus, the application of the correct CO2 overpressure suppressed at this elevated temperature both the growth and the formation of volatile products, so both were typical of our conventional lager beer according to example 4, "> while at the same time the reduced fermentation time of the High temperature fermentation according to Example 5 was achieved.

Example 7 i <>

The conditions for this fermentation were chosen so as to demonstrate that the suppression of both yeast growth and the formation of volatiles is directly related to the concentration of dissolved CO ₂ which is caused by the amount of excess CC pressure applied.

100 liters of the above-mentioned commercial wort were, as also stated above,: treated and subsequently fermented at a constant temperature of 22.2 ° C. under a constant CO2 overpressure of 0.98 atmospheres. As described above, a constant stirring speed of Maintain 33 revolutions / min. The concentration of dissolved CO2 in the liquid was 235 cm ³ of COi / cm ^{3 of} beer.

There was a total time of 102 hours (4.25 days) are needed to reach the end of fermentation on the basis of the features described above.

The yeast growth reached a maximum of 5.5 g / l dry weight, while the total concentration of volatile products relative to the GLC reference standard was 667 . As a result of the low volatile concentration, the odor was unacceptably mild for a typical lager beer.

Thus, the application of excessive COr overpressure at this elevated temperature suppresses both yeast growth and volatilization excessively compared to Example 4 which describes, for example, conventional lager fermentation and a raw beer . The reduced fermentation time was typical for this temperature.

The associated data for the fermentations described in Examples 4 to 7 are listed in the table

It is noteworthy that in all the examples carried out at the elevated temperature of 22 " C, the total fermentation time (the longest time required to satisfy the two characteristics of completion of fermentation ) was well below that of Example 4, which had been carried out at a storage fermentation temperature of 15.0 ° C.

Also noteworthy is the inverse relationship between the concentration of dissolved CO2 and both the maximum yeast growth and the concentration of volatile components. The figures are given in A b b. 2 graphically reproduced. It follows that with increasing concentration of dissolved CO2, the maximum yeast growth and the concentration of volatile constituents decrease. This relationship applies to the concentration of dissolved CO2 in all cases and is not dependent on the extent of the CO2 overpressure. This underscores the value of the discovery that the level of dissolved CO2 predominantly controls yeast growth and the concentration of volatiles; The CO2 overpressure is a mattel for adjusting the concentration of the dissolved CO2 to the required level. The knowledge of the influence of the fermentation temperature, the movement and the CO ₂ overpressure on the level of the dissolved CO 2 under supersaturated conditions is important for the determination of the extent of the CO ₂ overpressure, which is necessary for the yeast growth and the formation to the correct extent of volatile constituents to be suppressed to amounts that predominate in conventional lager fermentation.

Tabel

example 4th 5 6th 7th Temperature (C) 15.0 22.2 22.2 22.2 Stirring (rpm) yy 33 33 33 CO _r pressure (atü) 0 0 0.56 0.98 Yeast dry weight 5.9 6.45 5.9 5.52 (g / l) Concentration of dissolved 1.52 1.30 1.88 2.35 CO ₂ (cm ³ / cm ³ beer) *) End of the sugar assimi 178 85 95 80 lation (hours) Fermentation time to 0.10 ppm 172 89 93 102 Diacetyl (hours) Total content of curse 872 950 820 667 term substances (relative GLC peak range RPA) **)

*) The prevailing value during active fermentation **) Range relative to the internal standard rated 100.

For this purpose 2 sheets of drawings

Claims (3)

Patent claims: 1. A method for accelerated fermentation of a lager by sub-fermentation at elevated temperatures and CXV overpressures, characterized in that the fermentation at a temperature of 15.5 to 29.5 "C and a CCh counter pressure of 0.14 to 1.4 atmospheres during a time of 50 to 175 hours is carried out in such a way that during this time there is a concentration of dissolved CO2 of 1.5 to 2.0 cm ³ per cm ^{3 of} fermentation liquid in the fermentation liquid. 2. The method according to claim 1, characterized in that the temperature can be set to 15.5 ° C to 23.9 ⁰ C and the CO ₂ overpressure to 0.14 atü to 0.84 atü. 3. The method according to claim 2, characterized in that the temperature to 22.2 ° C and the CO2 overpressure can be set to 0.56 atm.