Studies On Changing Trends Of Amylases And The Effects Of Amylases And Proteases Activity On Saccharifying Products In The Process Of Beer Production

In this study, barleys and malts from Qingdao beer malt plant are used as studyobject. This study is conducted on the changing trends of α-amylase, β-amylase andlimit dextrinase activity during barely malt production, and the effects of amylasesand proteases activity on saccharifying products during mashing. This study not onlyprovides the theoretical basis for malt selection and preparation, but also provide thetheoretical guidance for controlling the fermentation degree and protein hydrolysisdegree in the process of mashing.Research on the changing trends of three amylases’ activity during maltproduction reveal that the malt sources have great effects on the amylases activity, andthe proportion of three kinds of amylase is different then commonly is:β-amylase>α-amylase>limit dextrinase. Therefore, the change of total amylaseactivity is mainly affected by the β-amylase activity. β-amylase activity is higher inthe raw, steeping the barley and the early of germination than the late of steeping. Incontrast, α-amylase and limit dextrinase activity are low in the raw, steeping thebarley and the early of germination, then mainly formation in barley germination. It isalso found that the thermal stability of α-amylase is better than β-amylase and limitdextrinase.In order to research the effects of amylases on saccharifying products, firstly,experimental designs for two enzymes (α-amylase, β-amylase) starch mashesconcludes that for given level of fermentable sugars, decreasing the activity of oneamylase enzyme could be compensated for by increasing the other’s activity.Secondly, experimental designs for three enzymes (α-amylase, β-amylase and limitdextrinase) starch mashes concludes that addition of limit dextrinase to the mashesresulte in a substantial increase in levels of fermentable sugars. And in starch hydrolysed to fermentable sugars as the index, the application of the SAS softwareacquired regression equation:Y2=51.18+0.85X1-1.06X2+6.17X3+1.34X12+0.017X1X2-0.97X1X3+1.91X22-0.53X2X3-0.43X32whereY2=starch hydrolysed to fermentable sugars(%)；X1=lg (units alpha-amylase activity)；X2=lg (units beta-amylase activity)；X3=lg (units limit dextrinase activity).In the research of the effects of proteases on protein hydrolysis degree, themethods of adding specific protease inhibitors had been uesd to determine theenzymes activity of metallopeptidase, serine peptidase, aspartic peptidase andcysteine peptidase. It is found that four kinds of protease inhibitors’ contributingconcentration respectively are: EDTA20mmol/L, PMSF5mmol/L, Peptide5umol/Land Iodine ethyl amide2mmol/L. In different malts total protease activity are almostequal while all kinds of proteases activity are different.In the process of germination, it is found that with the increasing of germinatingdays the changing trends of total protease, serine peptidase, metallopeptidase andcystsine peptidase are alomst firstly up then down, but the days when the enzymeactivity respectively reaching the highest are different. And the changing trend ofaspartate peptidase activity is not outstanding with the increasing of germinating, justhaving a little increasing in the ninth day.The method of adding papain and adjusting saccharifying condtions are used tofurther research the effects protease on degree of protein hydrolysis on the basis ofprotease contained in the barley. According to the single factor experiment,Box-Behnken combination experiment and application of the SAS software, it isconcludes regression equation and stable point which is the adding enzyme additivesfor139.4U/g, protein hydrolysis time56.78mins, protein hydrolysis temperature49.28℃.Y=18.36-0.00146X1+0.019X2-0.44X3-0.000051X12+0.000058X1X2+0.000249X1X3-0.000269X22+0.000067X2X3+0.004083X32 Where Y=degree of protein hydrolysis(%)；X1=the adding enzyme additives (U/g)；X2=protein hydrolysis time (min)；X3=protein hydrolysis temperature (℃).