Influence And Action Mechanism Of Different Concentration Zinc Ion In Malting System

There are9%～14%loss in malting process.It not only reduces the barley dry weight,but also increase the malting cost.Therefore we should reduce the malting loss to raise the economic benefit of malting industry in condition of ensuring the malt quality.During the respiration of barley active part,partial carbohyrate of barley are metabolized to CO2, H2O and enegy needed by vital movement in the tricarboxylic acid cycle.This partial consumption of barley is main source of respiration loss and malting loss.If we can find an enzyme in the tricarboxylic acid cycle which can be inhibited,the malting loss and respiration loss would be reduced.Malate dehydrogenase(MDH) which catalysis the transformation between oxaloacetic acid and MDH is a key enzyme in TCA cycle.Studies have shown that Zn2+have inhibitional effect to MDH.In this research,Sebastian barley,Schooner barley,Metcalfe barley and Chinese barley were used as test samples for malting,we added different concentrations of Zn2+in the last steeping and used blank group as control group.For finding out the best concentration which can reduce the activity of MDH and malting loss,and have no ngetive effect on the malt qualities,we determined the effect of different concentrations Zn2+on the activity of MDH, respiration loss, malting loss and the malt quality in the end of malting.We analyzed the inhibtion type of metal ion by kinetic of enzyme-catalyzed reaction.Finally,for finding the mechanism of action of Zn2+in barley, we determined dynamic distribution of Zn2+during barley germination.The result showed that the addition of zinc ion was found to restrain the activity of MDH in some quantity. Through that way, respiration of malt and the consume of sugar has been reduced, and the loss of malting has been brought down consequently. Adding0.3mmol/L Zn2+does not decrease breathing loss but instead promoting role,adding1.2mmol/L and2.1mmol/L Zn2+all can reduce loss of malting system,and the higher concentration the more obvious inhibition. Meanwhile, the influence on some significant quality of malt of the addition of zinc ion has been considered. We found that protein solubility and diastatic power would be reduced slightly and leaching efficiency increased with adding zinc ion appropriately. The content of Zn2+in main sprouting position within Sebastian and Schooner barley has been detected by colorimetric of dithizone. The influence of adding Zn2+in soaking barley has been taking into consideration as well. The result shows that, the motions of control group and experimental group, transport diffusion from endosperm and bran to the centre of embryo substantially, are generally identical.