Influence Of Post Disposal Methods On Beer Staling Level

Pasteurized beer is always sterilized at low temperature for long time or high temperaturefor short time, while the non-pasteurized draft beer is sterilized by physical filtering method toreach non-biological stability. Because of ‘low energy’ and retaining the original nutrition andflavor, non-pasteurized draft beer is widely favored by consumers. So, the market ofnon-pasteurized draft beer shows us a broad prospect. On the other hand, the high productioncost and poor stability of non-pasteurized draft beer make it a conundrum whether it’s good ornot. Therefore, the influences of membrane filtration and pasteurization on oxidation andanti-oxidation level of beer were studied in this study. The main research results are shown asfollows:Researches on the influence of heat process showed that TBA values raised as the heataction of beer went on. After heating at62℃for60min, the TBA value increased by12.17%mainly because of the increased of aging aldehydes by48.50%. During the heatingprocess, the content of SO₂decreased by73.33%after pasteurized for60min. The content oftotal polyphenols decreased and leaded the drop of DPPH clearance rate after the thermaleffect. At the same time, the increasing thermal temperature showed the similar effect onoxidation and anti-oxidation level as prolonged the pasteurization time. Beer sterilized at hightemperature for short time was better than that sterilized at low temperature for long time.Researches on the influence of micro-filtrition showed that the content of agingsubstances-aldehydes and the TBA value decreased by5.22%and2.13%after coarse andfine filtration in the closed environment respectively. The aging level of beer decreased andthe lag time extended after micro-filtrition. Compared to diatomite filtration, the process ofmicrofiltration would not introduce transition state metal ions. The anti-oxidation substanceSO₂mainly influenced the lag time of OH with R2=0.9369. Meanwhile, anti-oxidationsubstance polyphenols could slow down the OH generation rate, but made no contribution onlag time. The polyphenols could be retained during the membrane filtration process with theDPPH clearance rate dropped by5.70%. So, free radical generation rate of beer increased andthe anti-oxidation level of beer decreased.In this study, the index of aging and anti-aging levels in beer filtrated through0.45μmmembrane and that pasteurized at60℃for30minutes were compared. In all three samples,the content of aging precursors deceased by4.68%,16.53%, and7.03%after filtrationrespectively. Also, the content of aldehydes decreased. On the other hand, the content of agingprecursors deceased slightly after pasteurization. The staling compounds generated and thecontent of aldehydes increased by30.83%. The OH signal intensity in fresh pasteurized beerwas5times as much as that in non-pasteurized draft beer, while the stale flavor organoleptictaste grade of fresh pasteurized beer was equivalent to non-pasteurized beer that had alreadystored for one month.From the research results of oxidation level in non-pasteurized beer and pasteurized beer,it can be inferred that the tastes of draft beer and non-pasteurized draft beer with low hotbottle temperature were only better than pasteurized beer in one month. After storage for about one month, the tastes of draft beer and non-pasteurized draft beer with low hot bottletemperature were the worst. While, the taste of non-pasteurized beer with high hot bottletemperature was the best. The content of aging precursors made greater influence on beeraging rate compared to the content of antioxidants. During beer production peak seasons, thetechnique of low hot bottle temperature should be chosen. Moreover, the high hot bottletemperature should be chosen when off-season.