The Effects Of Zinc Ion On The Dissolution Extent Of Protein And Starch In Barley Germination Process

In this study, we explored the effect of Zn2+ on protein and starch dissolved when the Zn2+ could effectively reduce the malting loss, and researched some changes such as the protease activity, polyphenol oxidase, β-glucan and reducing sugar etc.In recent years, there are many reports to reduce the methods of malting loss, such as increasing barley layer of CO2 in the air, repeated steeping barley, adding potassium bromate and GA, and so on. Recent studies had shown that, Zn2+ may inhibit the Malate dehydrogenase that was one of the key enzymes of Respiration. So the malting loss could be reduced when adding at a concentration of Zn2+during the last steeping barley. However, this method reduced the malting loss, but also had an adverse effect on the quality of malt, which was a major obstacle to the application.In this research, the Australian barley Gairdner and domestic barley kenpi No.7 were used as test materials, specific studied the effect of Zn2+ on protein and starch dissolved when the Zn2+ could effectively reduce the malting loss. First, added different concentrations of Zn2+ solution when the last steeping, after germination measured respiration losses and malting loss, the best Zn2+ concentrations that can reduce malting loss was selected according to the relevant malt quality. In subsequent experiments, added the concentration of Zn2+ solution at the last steeping, we traced and checked the effect of Zn on the dissolution of protein and starch. Experiment with malt a-amino nitrogen content, KolbachOndex, saccharifying power, and the leaching efficiency as the main reference index, compared with control group was observed to identify the specific affect that the optimal Zn2+ concentration on malt protein and starch dissolved. The final,we combined the quality of the malt industry standards to optimize the application of additives.The test results showed that the 0.3 mmol/L,1.2 mmol/L,2.1 mmol/L Zn2+ in the experimental group,0.3 mmol/L Zn group malting losses increased, in addition to Zn could be reduced malting loss in both groups, and the higher the concentration of Zn2+ the inhibition was the more obvious. Based on this combination of malt quality need to choose to add 1.2 mmol/L Zn2+ and to research the effect of Zn2+ on protein and starch dissolved. The results showed that, Zn2+ had strong inhibition on the protein dissolved in the early germination, and the impact on the starch dissolved was weaker, in the late germination had a certain degree of inhibition on the starch dissolved. Meanwhile some malt quality indicators were compared, adding 1.2 mmol/L Zn2+, the a-amino nitrogen content, KolbachIndex, saccharifying power fairly basic compared with the control group, and the leaching efficiency, malt crispness value were basically the same with the control group. The indicators were able to achieve industry-standard malt. Preliminary results indicated that Zn2+ was indeed able to inhibit the malt dissolved when the malting loss was reduced, especially inhibitd the protein dissolved. But the inhibitory effect within the acceptable range, the study provided a theoretical basis for us that we could continue to study about how to add the Zn2+ to make malt quality better.