Biochemical Characteristics Of Brewing Barley Proteins

The extract process of albumins from barley seeds was studied by using quadraticorthogonal and rotary combination design method. The mathematic model was found Thebest factor is 9.1％the density of materials, 20℃lixiviation temperature and 3 hoursin lixiviation.Four species barleys were used to study the change in content of albumin duringgermination. Experimental results are showed as follows, the change of content of albumin indifferent barley seeds demonstrates more obvious regularity during germination, the contentof albumin is more time from 1.4 to 2.3 in malts germinated six days than in barley seeds.SDS-PAGE analysis showed that albumin in barley seeds was deficient in HMW proteincomponents, but rich in MMW and LMW protein subunits, and albumin subunits exists in thedistrict between 10 to 66 kilodalton. More spectral bands appeared in molecular weight of25～45 kilodalton separation than others during germination.Content changes for protein components, such as albumin, globulin, prolamin and glutenin,in germinating barley seeds were studied by using successive extraction and analysis ofprotein fractions. The albumin level was low in the barley seeds, when seeds germinated, thealbumins increased fast from 3％～5％to 10％, and its content was highest in the fourth dayafter germination while its level slightly decreased after baking in green malt. Content ofglobulins reached the peak 2 days after germination, from 3％to 6％. The prolamin contentdecreased gradually after germination, but increased slightly in the glutenin content.Two species barleys, Hordeum vulgare L. Kenpi No.8 and Hordeum vulgate L. Harringtowere used to study changes in contents of hordein, free amino acids and endopeptidaseactivity during germination. Results showed that the content of hordein in Kenpi 8 was higherthan that of Harrington, but decreased faster. The same tendency of free amino acids andendopeptidase activity in the two species barleys during germination. It implied that,compared with Harrington, the procedures of hordein break down and transfer to transportablenitrogen in Kenpi 8 was higher and faster during germination, and this maybe a importantreason of Kenpi 8 has potential to make high-quailty malt. Proteins in unmalted and malted barley and in BSG obtained after mashing werefractionated on the basis of their differential extractability in different media and characterisedby SDS-PAGE. Under non-reducing conditions, monomeric C hordeins and some B hordeinswere extracted from unmalted barley, whereas most if not all B, C and D hordeins wereextracted under reducing conditions. During malting, disulfide bonds are reduced and B and Dhordeins are broken down by proteolysis. No D hordeins were extracted from malt and nearlythe same levels of malt B hordeins were extracted both under nonreducing and reducingconditions. B hordeins present in BSG proteins were only extractable under reducingconditions. Whereas most of the C hordeins were extracted from BSG under non-reducingconditions, more C hordeins were extracted under reducing conditions. Mashing probablyinduced disulfide bond formation resulting in aggregation. Although earlier literaturesuggested the formation of an aggregate composed of B and D hordein (and glutelin) duringmashing, the present work suggests the formation of an aggregate composed of B hordeins inwhich C hordeins are entrapped.