Biochemical Characteristics And Influencing Factors Of Heat-stable Protein In Barley Seeds

Components and content of heat-stable protein (HSPs) in barley are essential for thequality of malt and beer. These proteins also have potential commercial value forextraordinary thermal resistance. A rapid and simple method was developed for extractingHSPs from barley, green malt and malt, and the extracts including malt-derived foam-activeproteins were subsequently analyzed, quantified and partial characterized by Bradford Methodand SDS-PAGE. It is notable that heat-stable proteins were involved fluctuations of quantityand resistant to endoproteolysis. In Sephadex G75elution, the HSPs extracts were separatedinto two major apex fractions with molecular weight approximate40kDa and12kDa.Intriguingly, the extracts and its40kDa fraction inhibited trypsin activity. All of this suggestedHSPs may play an important physiological role in germinating barley. These works laid thegroundwork for further research on structural and functional properties as well as its potentialcommercial value of the heat-stable proteins.HSPs was extracted from three barley cultivars grown in different geographic regions,which were subsequently quantified and analyzed by previous method. It is discovered thatcontent of HSPs was subject to decrease at germination, and significant differences werebetween varieties. Comparing the Australian cultivar, it is notable that HSPs of two Chinesecultivars was involved in more remarkable quantity fluctuations, and being higher amountlevel of LTP1rather than Protein Z. These results partially explained quality differencesbetween domestic and imported barley. It is anticipated that protein composition of domesticbarley should be optimized for brewing.PH is one of important environmental factors in malting. To determine the effect of pHon HSPs and malt-derived foam-active protein, content of the HSPs and relative amount ofProtein Z of barley and malt germinating at three different pH conditions were analyzed andquantified. It is discovered that pH3.0malting environment resulted on shrill decrease ofHSPs at steep stage, due to rapid phytase activation. Similarly, pH4.0increase Protein Z laterwith high amylase and proteinase activities on account of the tissue pH close to the optimum pH of endoenzymes.The procedure that extracting, analyzing and quantifing HSPs was stable and reliable topredict quality of malt and beer foam. It is anticipated that the methods could be applied toselect, manipulate and develop high-quality barley cultivars for breeders, as well asmanipulating malt for the brewing industries to improve beer foam stability.