Research On The Decline Of Draft Beer Foam Stability And Its Prevention Measures

Draft beer refers to the one with certain biological stability, which adopts the method of physical filter with no Pasteurization or instant high temperature sterilization. As a result, it remains the flavor and nutrients of fresh beer and thus is popular with consumers both at home and abroad. However, great defects have been seen in draft beer, that is, with the increase of shelf life, the foam stability fades away. The recession has already been the significant obstacle for the development of draft beer industry and troubled the manufacturers. Due to its unique technique, draft beer foam stability has been affected be several factors. Therefore, how to improve the draft beer foam stability has become a complicated subject.Draft beer is relatively a product in China and there is little systematic research on it. Focusing on draft beer foam stability, the paper puts much attention to the deciding factors, decline principle and control technology.l.Upgrade the technique for wheat selection, gluttonous, fermentation, storage and so forth and increase the content of foam-friendly materials, decrease harmful ones. In this way, foam stability has been greatly improved, the figure for finished products rises as high as more than 290s.2.There exists certain law for the decline. During early shelf life, it is mainly caused by active PrA; in the latter part, it is often cased by precursors. When the content of PrA is above 10-4TU, the stability will be affected to a high degree. Extraction of proteniase inhibitors from magic fungus through hot water and alcohol precipitation proves to be effective in inhibiting the PrA and its precursors in draft beer. Under certain circumstances, the inhibiting rate can be as high as 75%. The research indicates that the inhibitor works well in control the decline of foam stability for draft beer.3.The yeast activity exerts a great influence on the generation of PrA and its precursors. The lower activity, the more generation we see. Select the active yeasts as the seeding ones and limit them to acceptable generations and quantity. Recycle them within 1-2 generations, the utmost cells must be less than 1.3 107 /mL In the ferment process, make it early to recycle and discharge the yeasts thus to keep them active and prevent their death, aging and self-solution. In this way, the generation of PrA and its precursors will be effectively controlled.4.1n packaging stage, the finished beer will be processed with hot bottle method (60, 2.5 mins), which will damage the activity of PrA while preserve the activity of glucoamylase above 35%. As a result, the fresh draft beer is obtained while the foam stability is sustained as well.5.During the period between the initial filter and the ultimate one, addition of 35mg PGA/L to the draft beer will greatly increase the foam stability. It is found in experiments that beer with addition of PGA sees increase of 36.7% in foam stability after 5 minutes.