Decay Problems Of Draft Beer Foam Stability And Its Optimization

Draft beer refers that is not pasteurized after packaged or ultra hign temperature short time (UHT) before packing. More and more consumers focus on draft beer, because it can keep the original fresh flavor and nutrition. Compared with pasteurized beer, draft beer has obvious defects in the foam stability. With the extension of shelf life, the foam of draft beer decay seriously at the ambient temperature. Researches on the problem of draft beer foam stability have been a very long time. Raw materials, production process, the foam-positive proteins and proteinase A are responsible for products’foam quality. This paper mainly studies the decay of draft beer foam, as well as some optimization measures. The main research findings are summarized as follows:1Two batches of draft beer were placed at5℃, ambient temperature,40℃,50℃, storaged for six months. Different storage temperature has different effects on foam stability. Among them, pasteurized beer has the best foam stability. Its foam stability reaches180s in six month. The effect is much better than draft beer samples stored at other temperatures. Beer storaged at5℃and50℃conditions have better foam stability. Beer which were storaged at50℃use413-688minutes achieve the production’s sterilization requirements. At ambient temperature and40℃storage conditions, foam satbility of draft beer have much more serious decline. The foam attenuation-models of ambient temperature and40℃are as follows:The formula of foam decay model at ambient temperature storage conditions is:The formula of foam decay model at40℃storage conditions is:According to formulas of beer attenuation model, we can calculate the foam of draft beer at ambient temperature and40℃in any time of the six months. Provide valuable references for studying and improving draft beer foam stability.2Tracking four fermenters in large-scale production, we can get changes of proteinase A activity and high molecular protein content during fermentation. The main conclusions are summarized as follows:Yeast generated proteinase A. Proteinase A activity increased slowly prior to yeast harvesting with the highest levels of18.27-30.13U/mL. Subsequently, proteinase A activity reduced gradually. The results showed that the trends of high molecular weight protein and proteinase A activity had obvious difference between different fermentation vessels owing to their various fermentation parameters. High molecular weight protein decreased slowly during fermentation. From wort to finished beer, high molecular weight protein decreased from134-190mg/L. The high molecular weight protein was significant positive correlation with beer foam stability (r=0.794, P<0.01). There was no collection with proteinase A. In one month, draft beer foam stability has a huge decline about13-51s.3The research of process parameters on draft beer wort mashing:If the single factor was used for the response surface optimized combination, the model showed the higher significance, r=0.9926. The C (pH) in linear item had the significant influence on the high molecular weight protein content (P<0.01). The next was B (protein rest mode time)(P <0.01), but the A(protein rest mode temperature)had no influence(P>0.05). But the square and interactive items were very significant (P<0.01). The central combination design result showed that protein rest mode temperature was4℃, protein rest mode time was40.6min, and the pH value was5.3. In this condition, the high molecular weight protein content was up to605.94mg/L. The test was used to verify the technological parameter, and the result showed that the real high molecular weight protein content was607.24mg/L. Compared to prediction theory (605.94mg/L), the relative error was about0.21%.4Three different amounts of foam stabilizer (Tetra Iso-Extract, Hexa Iso-Extract, Alpha foam) added to draft beer, respectively. Tracking its foam stability, conclusions are as follows:(1) Three foam stabilizers improved draft beer foam stability significantly. The more addition added to the draft beer, the obviously enhance of foam stability. Adding1.92mg/L of Tetra Iso-Extract, after standing24h, beer foam increased25s.(2) In shelf life, draft beer foam stability has decreased significantly. By adding three kinds of foam stabilizers, beer foam stability decay solwly. The effects of three foam stabilizers are far from each other.(3) Adding beer foam stabilizers do not affect turbidity. Alpha Foam can increase slight bitterness of beer. Tetra Iso-Extract and Hexa Iso-Extract do not have a significant effect on the bitterness value.(4) The tasting results showed that there were no significant difference between beer and blanks. Scoring nine samples using comprehensive taste scoring method, part of the test beer’s scores are higher than blanks.There were no obvious differences in taste, bitterness, turbidity and other aspects between beer and blanks. After cost considerations, the amount of1.92mg/L Tetra Iso-Extract was selected as the most suitable addition for draft beer.