Study On The Preservation Technology Of Muddy Draught Beer By Ultra-high Pressure Processing

The muddy draught beer unfiltered, undiluted, without thermal sterilization and with characteristics of nutrient-rich, mellow and pure taste, loved by consumers. But its microbial system instability, flavor sensitive and storage difficult. In this paper, the muddy draught beer fermentation liquor as raw material, using the advantage of ultra-high pressure processing technology to carry on the effective sterilization of muddy draught beer while retaining its fresh flavor and good taste, evaluate its quality and to determine the product effective storage period.The main research results are as follows:1) The best flavor preservation technology of ultra-high pressure muddy draught beer is pressure of 300MPa, holding time of 15min, co-temperature of 25℃.The order of primary and secondary factors that ultra-high pressure influence the flavor of the muddy draught beer:pressure> co-temperature> holding time.2) Sterilization has meet the microbial limit requirements in 《green beer》 NY/T273-2012 and 《extraction and preparation of wine》 GB2758-2012 on the pressure of 300MPa, holding time of 15min and co-temperature of 25℃. Under this condition, the total number of colonies<15cfu/mL, E.coil<3MPN/mL, yeast, salmonella and staphylococcus aureus are Ocfu/mL. TBA value of the product is significantly lower than the threshold finished wine flavor; diacetyl and ethyl decanoate content significantly lower than the optimal level of wine threshold, flavor stability is good.3) The protein content of ultra-high pressure muddy draught beer is 7.3g/L, consistent with puree draft beer content and pasteurized turbid beer, than 4.1g/L in filter bacteria draft beer increased by 78%; ultra-high pressure muddy draught beer protein in vitro digestion rate of 89.92% that higher than pasteurized turbidity beer of 87.78% and 79.79% of the puree draft beer. These show that ultra-high pressure muddy draught beer nutrient-rich and ultra-high pressure processing can promote digestion and absorption of protein.4) The muddy draught beer with good preservation effect by the optimal conditions of ultra-high pressure. The value of TBA is 0.285 that lower than puree draft beer of 0.381 and pasteurized turbidity beer of 0.424.This shows that ultra-high pressure processing can inhibit aging beer to a certain extent; the content of diacetyl is 0.084mg/L, close to the puree draft beer of 0.079mg/L, significantly lower than the pasteurized turbidity beer of 0.127mg/L; and ethyl decanoate content of 0.817mg/L, close to the puree draft beer of 0.79mg/L, significantly lower than the pasteurized turbidity beer of 3.76mg/L.These show that the flavor of ultra-high pressure muddy draught beer is close to the fresh beer and significantly better than the pasteurized beer.5) The sensory quality, microbial and flavor of ultra-high pressure muddy draught beer are as examining index. Ultra-high pressure muddy draft beer in 4℃ storage six weeks away from light, the results show that microbial meet the limit requirements, and with good sensory quality and flavor preservation effect. Effectively prolong storage period compared to the untreated fresh beer five weeks, solved the problem of short shelf life of fresh beer to a certain extent.