Preliminary Research On Fresh Cloudy Wheat Beer Aging

With the rapid development of new technology of beer, the demand for the diversityconsumption was growing, protoplasmic beer got consumers to chase after hold in both handswith its fresh, unique flavor. Fresh cloudy wheat beer was a kind of protoplasmic wheat beer,it has the advantages of both wheat beer and protoplasmic beer: golden color, a typical malty,banana and spicy aroma, white, fine and smooth foam, excellent head retention, high carboncontent, strong taste, an excellent balance of fresh aroma and mellow taste, and theappearance of turbidity. But shorter shelflife became the key constraints factors of its rapiddevelopment. The research on fresh cloudy wheat beer was still in its infancy at home andabroad. In this research, the influences of the storage temperatures, sterilization intensityduring storage on fresh cloudy wheat beer aging were studied based on the determination oforganoleptic investigation, conventional physical and chemical indices, related aging indices,oxidative stability, flavor stability, foam stability. And the reasonable storage condition forfresh cloudy wheat beer was ascertained. The main results were as follow:(1)The aging of fresh cloudy wheat beer proceeded during the storage. Along with thestorage time extension, the organoleptic evaluation changed: an aged aroma and tastecharacter emerged, a sour and bitter taste appeared, foam and head retention declined. Thephysical and chemical indices changed: titratable acid and reducing sugar contents increased,pH value, viscosity and arabinoxylan content decreased. Related aging indices changed: colorand TBA value increased, turbidity decreased. Antioxidant ability decreased. Flavor stabilitychanged:4-VG content decreased after increased, acetaldehyde, higher alcohols contents andthe ratio of alcohols and esters increased, volatile esters content decreased. Foam stabilitychanged: foam retention, activity of protease A and foam protein content decreased, protein Zand lipid-transferred proteins LTP1contents decreased.(2)We compared the effects of four different storage temperatures (5,10,15,20oC) on theorganoleptic investigation, physical and chemical indices, related aging indices, antioxidantability, flavor and foam stability of fresh cloudy wheat beer, and came to a conclusion thathigh storage temperature could accelerate the aging process of fresh cloudy wheat beer. Alongwith the increase of storage temperature, increase of aged aroma and taste, sourness andbitterness quickened significantly, decayed of full-bodied taste and head retention accelerated.pH value and viscosity decreased, color, FRAP value, acetaldehyde and higher alcoholscontents increased. Higher storage temperatures (higher than20oC) would weaken the foam retention and lessen foam protein content. Storage temperature had no effect on araboxylancontent, TBA valu and O2·-radical scavenging activity. Effect on the titratable acid,-AN,reducing sugar and polyphenol contents, DPPH, ABTS radical scavenging activity,4-VG andvolatile esters contents, the ratio of alcohols and esters were relatively unconspicuous. Effecton activity of protease A and foam-positive protein were not clear. It was manifest that freshcloudy wheat beer kept the best sapor and flavor when stored for up to9days at5oC,6daysat10oC.(3)We compared the effects of three different intensity of sterilization (unsterilized,10PUUHT,20PU pasteurization) on the organoleptic investigation, physical and chemical indices,related aging indices, antioxidant ability, flavor and foam stability of fresh cloudy wheat beer,and came to a conclusion that sterilization could accelerate the aging process of fresh cloudywheat beer. Sterilization could increase the sourness, harsh after bitterness and aging flavor,reduce full-bodied taste. Sterilization could decline-AN content, increase titratable acid,acetaldehyde and higher alcohols contents, speed up the decline of4-VG content. Sterilizationhad no effect on pH value, reducing sugar, arabinoxylan, polyphenol, volatile esters contents,the ratio of alcohols and esters, foam retention, foam protein and foam-positive proteincontents. In addition, long with the increase of intensity of sterilization, color and TBA valueincreased, turbidity declined. Higher intensity of sterilization (20PU) had a negative effect onactivity of protease A. Fresh cloudy wheat beer could keep an excellent potableness with nonsterilization.(4)During the aging process of fresh cloudy wheat beer, sensory evaluation, color, turbidity,antioxidant ability (DPPH, FRAP, O2·-method), flavor substances and foam stability could beused for evaluation of aging degree.