Beer yeast propagation method and application thereof

Abstract

The invention relates to an expanding culture method and application of beer yeast, and relates to the technical field of beer brewing. The expanding culture method comprises the following steps: first-stage expanding culture: adding a culture medium inoculated with beer yeast into expanding culture wort, and carrying out first gradient oxygenation expanding culture to obtain a first expanding culture solution; second-stage expanding culture: adding the first expanding culture solution into expanding culture wort, and carrying out second gradient oxygenation expanding culture to obtain a second expanding culture solution; and third-stage expanding culture: adding the second expanding culture solution into expanding culture wort, and carrying out third gradient oxygenation expanding culture to obtain a third expanding culture solution which is used for fermentation. According to the expanding culture method, through a three-stage incremental oxygenation mode, the requirement of beer yeast for oxygen in different growth stages is well met, the growth and reproduction of the yeast are promoted, and the expanding culture efficiency is improved; the reasonable incremental oxygenation strategy is beneficial to optimizing the metabolic pathway of the yeast and improving the activity and fermentation performance of the yeast.

Description

Technical Field

[0001] The invention relates to the technical field of beer brewing, in particular to a method for expanding and culturing beer yeast and application thereof. Background Art

[0002] In the beer brewing process, yeast expansion is a key link. Adequate and reasonable oxygen supply is essential for yeast growth, reproduction and metabolism. The traditional oxygenation method often maintains a constant oxygenation rate throughout the expansion process. This method may not fully meet the change in the demand for oxygen from yeast to yeast during the growth stage, thus affecting the activity of yeast and the quality of beer. Therefore, there is an urgent need for a method that can effectively expand beer yeast and maintain high and stable performance of the expanded yeast. Summary of the invention

[0003] In view of the above problems, the present invention provides a method for the expansion culture of brewer's yeast. The expansion culture method better meets the demand of brewer's yeast for oxygen at different growth stages through a three-stage incremental oxygenation method, promotes the growth and reproduction of yeast, and improves the expansion culture efficiency; a reasonable incremental oxygenation strategy helps to optimize the metabolic pathway of yeast and improve the vitality and fermentation performance of yeast.

[0004] In order to achieve the above object, the present invention provides a method for expanding the culture of brewer's yeast, comprising the following steps:

[0005] The first stage of expansion culture: adding the culture medium inoculated with beer yeast to the expansion wort, performing the first gradient oxygenation expansion culture, and obtaining the first expansion culture solution;

[0006] The second stage of expansion: adding the first expansion liquid to the expansion wort, performing a second gradient oxygenation expansion to obtain a second expansion liquid;

[0007] The third stage of expansion: adding the second expansion liquid to the expansion wort, performing a third gradient oxygenation expansion to obtain a third expansion liquid, and the third expansion liquid is used for fermentation.

[0008] In the process of studying the above technical problems, the inventors found that the reason why the yeast has problems such as performance decline after the expansion and growth in the yeast expansion link in the prior art is that the yeast expansion link often adopts a constant oxygenation mode for oxygenation expansion, and the expansion and growth stage is essentially a process in which the number of yeasts grows from a small number to a large number. The constant oxygenation is excessive for a small number of yeasts in the initial stage of yeast expansion, and the excessive oxygenation will affect the performance of the yeast, so that the yeast performance obtained by the expansion is different; at the same time, the excessive increase multiple in the later stage of expansion will bring more unfavorable beer flavors such as alcohol and aldehydes to the fermentation and reproduction process, thereby affecting the beer flavor. Therefore, the inventors proposed the above expansion method, which better meets the demand for oxygen of beer yeast at different growth stages through the three-stage incremental oxygenation method, promotes the growth and reproduction of yeast, and improves the expansion efficiency; a reasonable incremental oxygenation strategy helps to optimize the metabolic pathway of yeast and improve the vitality and fermentation performance of yeast.

[0009] In one embodiment, the first gradient oxygenation expansion training includes: an initial oxygenation rate of 3-7 NL / min, a terminal oxygenation rate of 28-32 NL / min, and an oxygenation speed of 0.8-1.2 NL / min per hour.

[0010] In one embodiment, the first gradient oxygenation expansion training includes: an initial oxygenation rate of 5-6NL / min, a terminal oxygenation rate of 29-30NL / min, an oxygenation speed of 1NL / min per hour; and intermittent oxygenation per hour.

[0011] In one embodiment, the second gradient oxygenation expansion training includes: an initial oxygenation rate of 8-12 NL / min, a terminal oxygenation rate of 33-38 NL / min, and an oxygenation speed of 0.8-1.2 NL / min per hour.

[0012] In one embodiment, the second gradient oxygenation expansion training includes: an initial oxygenation rate of 10-11 NL / min, a terminal oxygenation rate of 34-35 NL / min, an oxygenation speed of 1 NL / min per hour; and intermittent oxygenation per hour.

[0013] In one embodiment, the third gradient oxygenation expansion training includes: an initial oxygenation rate of 13-17 NL / min, a terminal oxygenation rate of 38-42 NL / min, and an oxygenation speed of 0.8-1.2 NL / min per hour.

[0014] In one embodiment, the third gradient oxygenation expansion training includes: an initial oxygenation rate of 15-16NL / min, a terminal oxygenation rate of 39-40NL / min, an oxygenation speed of 1NL / min per hour; and intermittent oxygenation per hour.

[0015] In one embodiment, the intermittent oxygenation includes: oxygenating for 1-3 minutes, stopping for 1-3 minutes, and cycling.

[0016] In one embodiment, the first gradient oxygen expansion training time is 22-26 hours, the second gradient oxygen expansion training time is 22-26 hours, and the third gradient oxygen expansion training time is 22-26 hours.

[0017] The invention also provides application of the expansion culture method in beer brewing.

[0018] The present invention also provides a beer brewing method, comprising saccharification, fermentation and sake filtration, wherein the fermentation step adopts the expansion method to expand the beer yeast.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The invention discloses a method for expanding the cultivation of brewer's yeast and an application thereof. The method for expanding the cultivation better meets the demand of brewer's yeast for oxygen at different growth stages through a three-stage incremental oxygenation mode, promotes the growth and reproduction of yeast, and improves the expansion efficiency. A reasonable incremental oxygenation strategy helps to optimize the metabolic pathway of yeast and improve the activity and fermentation performance of yeast. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a result diagram of yeast growth trend during the expansion process of an expansion tank (No. YPT01#) in Example 2;

[0022] Figure 2 This is a result diagram of yeast growth trend during the expansion process of the second expansion tank (numbered YPT02#) in Example 2;

[0023] Figure 3 This is a diagram showing the yeast growth trend during the expansion process in the third expansion tank (numbered YPT03#) in Example 2. DETAILED DESCRIPTION

[0024] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0026] source:

[0027] Unless otherwise specified, the reagents, materials, and equipment used in this example are all commercially available; the experimental methods are all conventional experimental methods in the art unless otherwise specified.

[0028] Example 1

[0029] 1. Determination of initial oxygenation rate, final oxygenation rate, and precautions for expansion culture.

[0030] 1. Determination of initial oxygenation rate.

[0031] (1) When the expansion tank is oxygenated, ensure that the wort in the tank is slightly bubbling during the oxygenation period. It should be noted that the foam in the expansion tank should not submerge the cleaning ball in the tank during the oxygenation period, otherwise there will be a risk of microbial contamination.

[0032] (2) According to the growth of yeast count after the initial oxygenation flow rate, the yeast count in the first expansion tank, the second expansion tank, and the third expansion tank, and combined with the oxygenation status in the above expansion tank, the most suitable initial oxygenation rate for the first gradient oxygenation expansion is 5-6 NL / min, the initial oxygenation rate for the second gradient oxygenation expansion is 10-11 NL / min, and the initial oxygenation rate for the third gradient oxygenation expansion is 15-16 NL / min.

[0033] 2. Determination of terminal oxygenation rate.

[0034] On the one hand, according to the requirements of the beer yeast expansion process, the total expansion time of each stage needs to be controlled within 24 hours, and the increasing rate of 1NL / min per hour is relatively stable, so the terminal oxygenation rate is designed. On the other hand, according to the calculation formula of the incremental flow data set by the equipment program (as shown in Formula 1), the incremental data is obtained and verified with the terminal oxygenation rate and incremental data designed above. The two are consistent to determine the terminal oxygenation rate.

[0035] Formula 1: Current flow rate = (final oxygenation rate - initial oxygenation rate / set expansion time) × oxygenation time + initial oxygenation rate

[0036] The incremental results obtained by the data calculation method based on the actual operation of the incremental expansion training are also consistent with the incremental increase of 1NL / min per hour. Therefore, the terminal oxygenation rate of the first gradient oxygenation expansion training is determined to be 29-30NL / min, the terminal oxygenation rate of the second gradient oxygenation expansion training is 34-35NL / min, and the terminal oxygenation rate of the third gradient oxygenation expansion training is 39-40NL / min.

[0037] 2. A method for expanding the culture of brewer's yeast.

[0038] 1. Preparation stage: Select high-quality yeast strains and inoculate them into a Karlsruhe jar containing a basic culture medium. The initial inoculation volume is 80 L to obtain a culture medium for inoculating brewer's yeast.

[0039] 2. First stage of expansion cultivation: 5HL of expansion wort is taken from an expansion tank, and the culture medium inoculated with brewer's yeast is put into an expansion tank. The total time of expansion cultivation is controlled within 24 hours, and the oxygenation rate is controlled from the initial oxygenation rate of 5-6NL / min to the final oxygenation rate of 29-30NL / min. The process is to increase by 1NL / min per hour and adjust the growth by the expansion program to obtain the first expansion culture liquid. In this embodiment, the oxygenation mode per hour is intermittent oxygenation (oxygenation for 2min, stop for 2min, and repeat). For example, when the oxygenation rate in the first hour is 5NL / min, then in the first hour, oxygenation is performed at an oxygenation rate of 5NL / min for 2min and stop for 2min, and the cycle is performed until the oxygenation rate in the second hour increases to 6NL / min, and then in the second hour, oxygenation is performed at an oxygenation rate of 6NL / min for 2min and stop for 2min, and the cycle is performed, and so on.

[0040] 3. Second stage of expansion: Take 45HL of expansion wort from the second expansion tank, and pump the first expansion liquid in the first expansion tank into the second expansion tank. The total expansion time is controlled within 24 hours. The oxygenation rate is controlled from the initial oxygenation rate of 10-11NL / min to the final oxygenation rate of 34-35NL / min. The process is to increase by 1NL / min per hour and adjust the growth by the expansion program to obtain the second expansion liquid. The oxygenation method for the second stage of expansion per hour is intermittent oxygenation.

[0041] 4. The third stage of expansion: Take 180HL of expansion wort from the third expansion tank, and pump the second expansion liquid in the second expansion tank into the third expansion tank. The total expansion time is controlled within 24 hours, and the oxygenation rate is controlled from the initial oxygenation rate of 15-16NL / min to the final oxygenation rate of 39-40NL / min. The process is to increase by 1NL / min every hour and the expansion program is used to adjust the growth. The oxygenation method for the third stage of expansion every hour is intermittent oxygenation.

[0042] 5. At the end of the third stage, the expanded culture in the three expansion tanks is moved into the fermentation tank for production fermentation.

[0043] During the entire expansion process, the temperature of the culture medium, the number of yeasts, the yeast tooth rate, the sugar content of the expansion liquid, the fermentation degree, the alcohol content and other parameters are monitored in real time, and corresponding adjustments are made according to the monitoring results. The equipment of each factory varies in size, and the specific expansion inoculation amount and expansion process temperature control can be adjusted in combination with the equipment of the factory and the characteristics of the yeast strain to adjust the process parameters.

[0044] Example 2

[0045] Dongguan Zhujiang Beer adopted the expansion method of Example 1 to expand the culture of beer yeast.

[0046] 1. The actual parameter changes of the first expansion tank (numbered YPT01#), the second expansion tank (numbered YPT02#), and the third expansion tank (numbered YPT03#) during the expansion process are shown in the following table.

[0047] Table 1 Parameter changes of expansion tank (No. YPT01#)

[0048]

[0049] Table 2 Parameter changes of the second expansion tank (No. YPT02#)

[0050]

[0051] Table 3 Parameter changes of the third expansion tank (No. YPT03#)

[0052]

[0053]

[0054] 2. Monitoring of yeast fermentation data during the expansion process.

[0055] Expansion results: The yeast growth trend is good. The specific yeast count and yeast performance of each expansion tank are as follows: Figure 1 , Figure 2 , Figure 3 shown.

[0056] Table 4 - Yeast number and performance monitoring of expansion tank (No. YPT01#)

[0057]

[0058] Table 5 Number of yeasts cultured and performance monitoring in the second expansion tank (No. YPT02#)

[0059]

[0060] Table 6 Number of yeasts cultured and performance monitoring in three expansion tanks (No. YPT03#)

[0061]

[0062]

[0063] From the above table and Figure 1-3 It can be seen that during the incremental oxygenation period in each expansion tank, the yeast count increased steadily, and the expansion time was controlled at 24 hours, which met the process requirements.

[0064] Example 3

[0065] 1. The same type of brewing yeast was cultured using the expansion method of Example 1 (the oxygenation flow rate and valve opening parameters in each expansion tank were the same as those in Example 2) and conventional fixed intermittent oxygenation, and the fermentation performance of the final expanded yeast was compared. The results are shown in the following table. The fermentation process and yeast performance and flavor of the incremental oxygenation process are better than those of the conventional fixed intermittent process.

[0066] Conventional fixed intermittent oxygenation means: the oxygenation flow rate is fixed to a value between 25-30NL / min, oxygenation for 2 minutes, stop for 2 minutes, and repeat. The total time is 24 hours.

[0067] In this embodiment, the oxygenation flow rate is selected to be 28NL / min, oxygenation is performed for 2 minutes, and then stopped for 2 minutes, and the process is repeated, with a total time of 24 hours.

[0068] Table 7 Comparison of yeast fermentation performance obtained by the expansion method of Example 1 and conventional fixed intermittent oxygenation expansion

[0069]

[0070]

[0071] Table 8 Comparison of yeast fermentation performance obtained by the expansion method of Example 1 and conventional fixed intermittent oxygenation expansion

[0072]

[0073] 2. It can be found from the data in the above table that by using the expansion method of Example 1, the yeast mortality rate at each stage of yeast expansion is basically controlled within 1%, and the effect is good. The fermentation process using incremental intermittent oxygenation is normal, the sugar reduction rate is 2.7 / day, and the diacetyl reduction time is better controlled at about 7 days. The recovery concentration of 0-degree yeast using incremental intermittent oxygenation does not change much, and the recovery yeast activity is better than the result obtained by expansion by fixed intermittent oxygenation, which can be increased by up to about 1.5%. Compared with the previous conventional expansion method (i.e., expansion by fixed intermittent oxygenation), the number of suspended yeast at 0 degrees is lower. The flavor substances, acetaldehyde and total alcohol of the same variety of wine are lower than those of the fixed intermittent oxygenation process.

[0074] Example 4

[0075] Experiments were performed with different initial oxygenation rates.

[0076] 1. Test 1: The initial oxygenation rate is low.

[0077] 1. The specific parameters of the three-stage expansion training are as follows:

[0078] YPT01#: The expansion time is set to 24 hours, the initial flow rate is 1NL / min, and the final flow rate is 25NL / min;

[0079] YPT02#: The expansion time is set to 24 hours, the initial flow rate is 5NL / min, and the final flow rate is 29NL / min;

[0080] YPT03#: The expansion time is set to 24 hours, the initial flow rate is 10NL / min, and the final flow rate is 34NL / min.

[0081] 2. Result: It does not meet the process requirements of 24-hour expansion (the number of yeast transferred to each expansion tank is required to be ≥80*10 6 The expansion time required for the final yeast count to reach the standard and the yeast count achieved are shown in the following table.

[0082] Table 9 Yeast quantity of each expansion tank

[0083]

[0084]

[0085] Experiment 1: The yeast was slow to initiate in the early stage of each expansion tank, and only started to grow and reproduce normally after 6-8 hours, resulting in a long expansion time that did not meet the overall expansion process requirements. Insufficient oxygen supply to the yeast in the early stage of expansion led to slow initiation.

[0086] 2. Test 2: Start the test with the oxygen flow rate at a high level.

[0087] 1. The specific parameters of the three-stage expansion training are as follows:

[0088] YPT01#: The expansion time is set to 24 hours, the initial flow rate is 10NL / min, and the final flow rate is 34NL / min.

[0089] YPT02#: The expansion time is set to 24 hours, the initial flow rate is 15NL / min, and the final flow rate is 39NL / min

[0090] YPT03#: The expansion time is set to 24 hours, the initial flow rate is 20NL / min, and the final flow rate is 44NL / min.

[0091] 2. Result: It does not meet the process requirements of 24-hour expansion (the number of yeast transferred to each expansion tank is required to be ≥80*10 6 / ml, expansion time 24 hours), as shown in the following table.

[0092] Table 10 Yeast quantity of each expansion tank

[0093] Expansion tank number Expansion time H <![CDATA[Final yeast count (10 6 cells / ml)]]> YPT01 18 120.4 YPT02 17 118.5 YPT03 18 123.2

[0094] Experiment 2: The overall expansion time was too short, the yeast growth rate was too fast, the expansion time was short and the yeast count in each expansion tank exceeded 100*10 at the end of the expansion 6 If the oxygen supply is above 100%, it means that the amount of oxygen is too large, resulting in a high yeast count and excessive yeast proliferation, which will produce too many flavor substances that are not conducive to beer, and increase the oxidation of the wine body and yeast.

[0095] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0096] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for propagating brewer's yeast, characterized in that: The following steps are involved: The first stage of expansion culture: adding the culture medium inoculated with beer yeast to the expansion wort, performing the first gradient oxygenation expansion culture, and obtaining the first expansion culture solution; The second stage of expansion: adding the first expansion liquid to the expansion wort, performing a second gradient oxygenation expansion to obtain a second expansion liquid; The third stage of expansion: adding the second expansion liquid to the expansion wort, performing a third gradient oxygenation expansion to obtain a third expansion liquid, and the third expansion liquid is used for fermentation.

2. The method for expanding the culture according to claim 1, characterized in that: The first gradient oxygenation expansion training includes: an initial oxygenation rate of 3-7 NL / min, a terminal oxygenation rate of 28-32 NL / min, and an oxygenation speed of 0.8-1.2 NL / min per hour.

3. The method for expanding the culture according to claim 2, characterized in that: The first gradient oxygenation expansion training includes: an initial oxygenation rate of 5-6NL / min, a terminal oxygenation rate of 29-30NL / min, an oxygenation speed of 1NL / min per hour; and intermittent oxygenation per hour.

4. The method for expanding the culture according to claim 1, characterized in that: The second gradient oxygenation expansion training includes: an initial oxygenation rate of 8-12 NL / min, a terminal oxygenation rate of 33-38 NL / min, and an oxygenation speed of 0.8-1.2 NL / min per hour.

5. The method for expanding the culture according to claim 4, characterized in that: The second gradient oxygenation expansion training includes: an initial oxygenation rate of 10-11 NL / min, a terminal oxygenation rate of 34-35 NL / min, an oxygenation speed of 1 NL / min per hour; and intermittent oxygenation per hour.

6. The method for expanding the culture according to claim 1, characterized in that: The third gradient oxygenation expansion training includes: an initial oxygenation rate of 13-17 NL / min, a terminal oxygenation rate of 38-42 NL / min, and an oxygenation speed of 0.8-1.2 NL / min per hour.

7. The method for expanding the culture according to claim 6, characterized in that: The third gradient oxygenation expansion training includes: an initial oxygenation rate of 15-16NL / min, a terminal oxygenation rate of 39-40NL / min, an oxygenation speed of 1NL / min per hour; and intermittent oxygenation per hour.

8. The method for expanding the culture according to any one of claims 1 to 7, characterized in that: The time of the first gradient oxygenation expansion training is 22-26 hours, the time of the second gradient oxygenation expansion training is 22-26 hours, and the time of the third gradient oxygenation expansion training is 22-26 hours.

9. Application of the culture expansion method according to any one of claims 1 to 8 in beer brewing.

10. A method for brewing beer, characterized in that: The method comprises saccharification, fermentation and sake filtration, wherein the fermentation step adopts the expansion method according to any one of claims 1 to 8 to expand the brewer's yeast.

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