Study on the technology of producing wheat beer by secondary fermentation

Secondary fermented wheat beer is a beer produced by using the upper fermentation yeast No.354 and the lower fermentation yeast No.308 as production strains, using wheat malt and special malt as raw materials, through the main fermentation of the upper fermentation and the post-fermentation of the lower fermentation. . It is favored by consumers for its pure taste, elegance and softness, unique ester fragrance, rich mellow fragrance, white and delicate foam, and strong killing power. In particular, the characteristic aroma produced by the fermentation yeast above is more fragrant, pleasant and refreshing. We have made a beneficial attempt on the secondary fermentation wheat beer process by using the one-pot method.

Raw materials and requirements for secondary fermentation of wheat beer

Yeast

Special yeast for secondary fermentation wheat beer production: upper fermentation yeast No.354 and lower fermentation yeast No.308.

Malt

Barley Malt, Wheat Malt and Specialty Malts.

Hops

Bitter granules are type 90 and fragrant granules are type 45.

Brewing water

Complies with the brewing water with a temporary hardness of 0.358 to 0.537 mmol/L and a total hardness of 0.895 to 1.79 mmol/L.

The production process of secondary fermented wheat beer

1. Wort preparation

(1) Saccharification process

The barley malt, wheat malt and caramel malt were weighed according to the mass percentage required by the saccharification process, and saccharified. For example, the saccharification process can be set to: 37℃～44℃～48℃～53℃～65℃～75℃～78℃ (the specific temperature and time setting should refer to the raw material parameters used for specific setting).

(2) Wort filtration

The following points need to be paid attention to in wort filtration: First, use hot water at 75°C to 78°C to spread water on the bottom of the sieve plate to discharge the air in the middle, and preheat the sieve plate to prevent the sudden cooling of the wheat mash from affecting the filtration. After the saccharified mash enters the filter tank, let it stand for 10 minutes, and the mash naturally settles to form a filter layer, which is extremely important for forming a filter layer with good permeability and high uniformity. Furthermore, the wort reflux speed should not be too fast to prevent the wort from being sucked to death and affecting the filtration speed and quality. The temperature of the dregs water has been maintained at 76~78℃.

(3) Boil the wort and add hops

The addition of hops adopts the secondary addition process. For the first time, add 90-type bitter-type granular hops 10 minutes after boiling; for the second time, add 45-type aroma-type granular hops 10 minutes before the end of boiling.

(4) Wort post-processing

After the hot wort is beaten, it enters the rotary sedimentation tank. The wort was left to stand for 30min in the gyratory sedimentation tank. Then, the wort is cooled by a thin-plate cooler, and oxygen is supplied in an amount of 8-10 mg/L.

2. Expanded culture of secondary fermentation wheat brewer's yeast

Including the expansion of two strains of the upper fermentation yeast No.354 and the lower fermentation yeast No.308.

(1) Yeast expansion culture

Inclined surface → plate marking → liquid test tube → 200mL conical flask → 1000 mL conical flask → 5000 mL conical flask → 100L yeast expansion tank → 1000L fermentation tank

(2) Hygiene

Containers, valves, inoculation ports, and pipes during expansion should be thoroughly cleaned and sterilized.

(3) Changes in yeast quantity, germination rate and sugar content

Pay attention to detecting the number of yeast cells and germination rate. When the number of yeast is 40-50×106/ml, it is connected to the fermenter.

3. Fermentation process

Due to the use of different strains, the fermentation process of secondary fermented wheat beer is different from that of ordinary beer.

(1) Primary fermentation

The main fermentation uses the upper fermentation yeast No. 354, and the purpose is mainly to obtain the characteristic flavor substances of the upper fermentation beer. Drop the yeast at 12°C into the first pot of wort. After the yeast proliferates in the fermenter for 8-10 hours, it is pumped into the second pot of wort to continue fermentation. Diacetyl is an important indicator of whether the beer is mature or not, so it should be closely watched for changes.

(2) Post fermentation

The post-fermentation uses the following fermentation yeast No.308, the main purpose is to saturate the CO2 in the beer and make the beer taste more plump. After the upper fermenting yeast is discharged, an appropriate percentage of 11°P wort and the lower fermenting yeast are added to the fermentation tank for post-fermentation. Fermented at 5℃ for 5d, then cooled to 0℃, and entered the stage of post-fermentation wine storage.

(3) After storage

The temperature of the post-storage wine is -1±0.5℃, the yeast is discharged every 3d during the wine storage period, the post-storage tank pressure is maintained at 0.13~0.15MPa, and the whole fermentation period is 28d.

4. Filtration and filling

(1) Filter

The protein content of secondary fermented wheat beer is higher, the suspension of yeast is stronger, and it is slightly more difficult to filter than ordinary beer, so it should be paid enough attention. Drain the yeast one more time before filtering.

(2) Filling

Pay attention to the adjustment of the filling pressure, and the bottle neck air should be as low as possible.

Quality of finished beer

1. Sensory quality

The appearance is clear, transparent and shiny; the foam is white and delicate, and it can be hung for a long time; Has the typical taste profile of secondary fermented wheat beers.

2. Physical and chemical indicators

Alcohol content 5.2%, original wort concentration 11°P, true fermentation degree 68.6%, diacetyl 0.07mg/L, total acid ml/100ml, chroma 25EBC, turbidity 0.6EBC, bubble retention 291s, carbon dioxide 5.5mg /L, bitter quality 26BU.

Conclusion

The physical and chemical and hygienic indicators of the product meet the national standards; the appearance quality is good, the taste is good, the physical and chemical indicators are in line with the standard, and it has the typical taste characteristics of secondary fermented wheat beer.