Zinc Matt And Fermentation Performance Of The Franco-wheat System

Zinc is a vital trace element to human, and barley, which has large ability of trace element- accumulation, is the main stuff of beer brewing. Starting from malting and fermentation, which were two primary biological process in the course of beer production, this article discussed Zn-enrichment and the distribution of organic zinc in barley, the physiology and biochemical character of malt and the brewing quality of product malt. This article also studied the effects of enriched-Zn malt on biological characteristic of beer yeast and beer fermentation. The results were as follows:(l)Malt had powerful ability of accumulating zinc and transforming inorganic-Zn into organic-Zn, and the best conditions were 150mg L^-1 concentration of ZnSO₄, 0.10mg L^-1 concentration of gibberellin GA3 12℃ water temperature and 41.8% malt soaking degree. The content of organic zinc in malt reached to 97.0 and 150.9ug g^-1, it was 20.3 and 2.35 times of the controls, respectively, and the highest velocity of Zn-enrichment was 36.00ug g^-1-day^-1 after 36 hours of germination, the percentage of zinc in protein and polysaccharides was 66% and 23% of overall organic zinc, respectively, and 90% of organic zinc existed in protein and polysaccharides. Most of zinc absorbed by malt combined with protein and polysaccharides. Changes of zinc concentration in protein and polysaccharides were discussed in this paper. The protein and polysaccharides content increased when the malt was treated with lower concentration of ZnSO₄. High concentration GA3 increased the content of protein, and lower concentration did the content of polysaccharides. From 0 to 150mg L^-1, the ZnSO₄ increased respiratory intensity of malt and the activity of α-and β-amylase, protease, peroxidase and polyphenoloxidase and free α-AN in malt. 100²00mg-L^-1 of ZnSO₄ could remarkably improve the quality of malt. Gibberellin GA3 increased the activity of a-and β-amylase in malt. 0.05-0.10mg L^-1 of GA₃ could remarkably improve the quality of malt, too.(2)Beer yeast grew full out when incubated with enriched-Zn malt of 100²50 mg L^-1. Enriched- Zn malt of 0²50mg L^-1 were in favor of the improvement of yeast's fermentation rate. Yeast's rate of flocculation was highest when incubated with enriched-Zn malt of 150mg L^-1, reaching to 0.53, while the control was 0.42. Yeast propagated most quickly when cultivated with enriched-Zn malt of 250mg-L^-1(3)The pH value was under the control when fermented with enriched-Zn malt.Enriched-Zn malt stimulated yeast's growth. Attenuation of 150mg L^-1 and absorption of α-AN of 200mg L^-1 enriched-Zn malt were best, respectively. Total acid of 50 and 150mg L^-1 was beyond the control. Enriched-Zn malt reduced the content of higher alcohols and diacetyl in beer. Enriched-Zn malt of 150²50mg L^-1 enhanced attenuation final degree and alcoholicity. Enriched-Zn malt of 100²50mgL^-1 accelerated the absorption of zinc. The absorptance and absorption number of organic zinc were highest, reaching to 63.8% and 0.94mg L^-1, respectively, when fermented with enriched-Zn malt of 100 mg L^-1 and 150mg L^-1.The researches showed that treatment of ZnSO₄ enhanced organic zinc content in malt, improved the quality of malt and that enriched-Zn malt promoted biological activity of beer yeast and influenced the process of beer brewing. These researches provided a theoretical basis for the production of enriched-Zn malt and the development of enriched-Zn beer.