Studies On The Barley Carbohydrases And Their Activity In The Malt Production

In this study, diffient barley varieties were used as experimental materials, including the domestic barley and imported barley. The study was conducted on the activity ofα-amylase,β-amylase and limit dextrinase during barley malt production, including the dynamic changes of enzyme activity, the methods to improve activity, and the purification and character of limit dextrinase. This study not only provide the theoretical basis for malt selection and Preparation, but also provides the materials and technology to study the quality of domestic barley and carbohydrases.Research on the dynamic changes of three enzyme activity malt production revealed that,β-amylase activity was already very high in ungerminated barley seeds while the activity ofα-amylase and limit dextrinase were very poor. The activity of the carbohydrases depressed during Steeping course, but rise rapid in the barley germination.The limit dextrinase have three distinct forms in barley germination: free limit dextrinase, latent limit dextrinase and bound limit dextrinase. The total activity of limit dextrinase developed slowly in the early germination, whice is lagger thanα-amylase andβ-amylase.It reached the highest activity when germinated for 4 or 5 days.By the reason of diffient thermal stability, the activity of limit dextrinase andβ-amylase depressed significantly, whileα-amylase's was littlt effected. The study also shows that, the activity ofα-amylase,β-amylase and limit dextrinase were different from varieties.The study was conducted on the dynamic changes ofα-amylase,β-amylase and limit dextrinase during the barley sprouting course by adding different materials (metal ions and GA₃), and compared differences of three carbohydrases to get the optimum amount of additives. The results indicated that adding different materials (metal ions and GA3) could effect the activity ofα-amylase,β-amylase and limit dextrinase and shorten the time for malt production, especially composite using metal ions and GA3.According to experiments, the optimum amount are as follows: Mg²⁺ 50mg/kg, Ca²⁺50mg/kg, Zn²⁺ 20mg/kg, K⁺ 80mg/kg, Na⁺ 80mg/kg, GA₃ 0.5mg/kg.As the most importance enzyme impacting the degree of wort fermentation, limit dextrinase came hot in the barley amylase research.In this experience, pure limit dextrinase was abtained with simpler purification method. The activity is 14.4 mU/mg, 20.8 times than the crude enzyme, with the recovery was 17.5%. The enzyme had high specific activity, was homogeneous, and gave single bands of protein when examined by SDS-PAGE(-98kDa). The pH valueand temperature for optimum catalysis of crude enzyme was 5.5 and 40℃, respectively. The thermal stability and pH stability was poor.