Secondary fermented wheat beer is produced by using upper fermentation yeast No.354 and lower fermentation yeast No.308 as production strains, and using wheat malt and specialty malt as raw materials. It undergoes both upper fermentation and lower fermentation to achieve its distinctive characteristics. Consumers appreciate its pure taste, elegance, softness, unique ester fragrance, rich mellow aroma, white and delicate foam, and strong drinkability. The aroma produced by the upper fermentation yeast is particularly fragrant, pleasant, and refreshing. We have successfully explored the one-pot method for the production of secondary fermented wheat beer.
Raw Materials and Requirements for Secondary Fermentation of Wheat Beer
The special yeasts used for the production of secondary fermented wheat beer are upper fermentation yeast No.354 and lower fermentation yeast No.308.
The malt varieties used include barley malt, wheat malt, and specialty malts.
Bitter hops (type 90) and aromatic hops (type 45) are used.
The brewing water should have a temporary hardness of 0.358-0.537 mmol/L and a total hardness of 0.895-1.79 mmol/L.
Production Process of Secondary Fermented Wheat Beer
1. Wort Preparation
(1) Saccharification Process
Weigh the barley malt, wheat malt, and caramel malt according to the required mass percentage for the saccharification process. The saccharification process may involve temperature steps such as 37℃ → 44℃ → 48℃ → 53℃ → 65℃ → 75℃ → 78℃ (specific temperature and time settings should be determined based on the raw material parameters).
(2) Wort Filtration
During wort filtration, it is important to use hot water at 75°C to 78°C to wet the sieve plate and remove air bubbles. The filter tank should be allowed to stand for 10 minutes after the saccharified mash is transferred, allowing the mash to settle and form a permeable and uniform filter layer. The speed of wort reflux should not be too fast to ensure the quality and efficiency of filtration. The temperature of the spent grains water should be maintained at 76-78℃.
(3) Wort Boiling and Hops Addition
Hops are added in two stages. Type 90 bitter hops are added 10 minutes after boiling begins, followed by type 45 aromatic hops added 10 minutes before the end of boiling.
(4) Post-processing of Wort
The hot wort is transferred to a rotary sedimentation tank and allowed to stand for 30 minutes. It is then cooled using a plate cooler, with oxygen supplied at a rate of 8-10 mg/L.
2. Expansion Culture of Secondary Fermentation Yeast
This involves the expansion culture of both upper fermentation yeast No.354 and lower fermentation yeast No.308.
(1) Yeast Expansion Culture
The expansion process starts from an inclined surface, followed by plate marking, liquid test tube, 200mL conical flask, 1000mL conical flask, 5000mL conical flask, 100L yeast expansion tank, and finally a 1000L fermentation tank.
Containers, valves, inoculation ports, and pipes used during expansion should be thoroughly cleaned and sterilized.
(3) Monitoring Yeast Quantity, Viability, and Sugar Content
The yeast cell count and viability should be monitored. Yeast is connected to the fermenter when the cell count reaches 40-50×106/ml.
3. Fermentation Process
The fermentation process of secondary fermented wheat beer differs from that of regular beer due to the use of different strains.
(1) Primary Fermentation
The main fermentation uses upper fermentation yeast No.354 to obtain the characteristic flavor of upper fermentation beer. The yeast is added to the first batch of wort at 12℃. After 8-10 hours of yeast propagation in the fermenter, it is transferred to the second batch of wort for continued fermentation. Diacetyl levels should be monitored as an indicator of beer maturity.
(2) Secondary Fermentation
Secondary fermentation utilizes lower fermentation yeast No.308 to saturate the beer with CO2 and enhance its fullness. After the upper fermentation yeast is removed, a certain percentage of 11°P wort and the lower fermentation yeast are added to the fermentation tank for secondary fermentation. Fermentation is carried out at 5℃ for 5 days, followed by cooling to 0℃ for further post-fermentation aging.
The post-fermentation aging temperature should be maintained at -1±0.5℃. Yeast should be discharged every 3 days, and the pressure in the storage tank should be maintained at 0.13-0.15 MPa. The entire fermentation period lasts 28 days.
4. Filtration and Bottling
Due to the higher protein content and stronger yeast suspension in secondary fermented wheat beer, filtration may be slightly more challenging compared to regular beer. It is important to discharge the yeast once more before filtration.
The filling pressure should be carefully adjusted, and the bottle neck should contain as little air as possible.
Quality of the Finished Beer
1. Sensory Quality
The beer should have a clear, transparent, and shiny appearance. The foam should be white, delicate, and long-lasting. It should possess the typical flavor profile of secondary fermented wheat beers.
2. Physical and Chemical Indicators
The alcohol content should be 5.2%, original wort concentration 11°P, true fermentation degree 68.6%, diacetyl content 0.07mg/L, total acidity ml/100ml, color intensity 25EBC, turbidity 0.6EBC, bubble retention 291s, carbon dioxide 5.5mg/L, and bitterness 26BU.
The physical, chemical, and hygienic indicators of the product meet national standards. The beer has good appearance quality, pleasant taste, and its physical and chemical indicators are within the standard range. It possesses the typical flavor characteristics of secondary fermented wheat beer.