Bacterial community composition shifts in sediments influenced by fish feeds

This study investigated the influence of fish feed deposition on the microbial community of sediments in a coastal lake. Microcosms were designed to simulate the addition of fish feeds to the sediment, and physicochemical factors as well as composition of microbial assemblages were analysed. Although total organic carbon and total organic nitrogen did not significantly increase, redox potential and total sulphides showed a transition of sediment environments into anaerobic condition due to the addition of fish feeds. The bacterial community composition shifted with fish feed deposition as revealed by the band profiles of denaturing gradient gel electrophoresis, Sørensen's similarity indices and cell numbers of sulphate‐reducing bacteria. Occurrence of anaerobic bacteria (sulphate and nitrate reducers) and disappearance of strictly aerobic bacteria were observed with fish feed inputs. The results clarify the succession of the microbial flora and suggest negative impact of uneaten fish feeds on the microbial community in sediment and resultant environmental deterioration of fish‐farming areas.     

微量沉淀值和麦谷蛋白亚基组成对面包烘烤品质的效应

为快速高效地改良中国小麦品种的面包烘烤品质,将72份冬小麦品种(系)于2000～2001年度分别种植于河南郑州和山东济南,分析了它们的蛋白质品质和面包烘烤品质,评价了蛋白质含量、微量沉淀值及高、低分子量麦谷蛋白亚基组成对面包烘烤品质的作用.结果表明,总体上中国冬小麦品种的蛋白质含量和微量沉淀值中等偏高,面包烘烤品质则较差,品种间差别较大.高、低分子量麦谷蛋白亚基的等位变异与面包烘烤品质密切相关,Glu-Dl位点具有5 10亚基和Glu-B3位点具有h亚基的品种,其面包各烘烤品质参数均显著优于具有其他亚基的品种,而Glu-B3j亚基(即1B/1R易位)对微量沉淀值、比沉淀值和面包体积、颈高、外观、质地、结构、色泽、评分等品质参数均具有较大的负向作用.沉淀值对非1B/1R易位系面包体积和评分的作用远大于蛋白质含量的贡献,而单位蛋白质含量的沉淀值即比沉淀值对1B/1R易位系的面包体积和评分更重要.在育种中应针对非1B/1R易位系和1B/1R易位系采用不同的品质改良策略,对非1B/1R易位系可考虑通过提高沉淀值,对1B/1R易位系则应考虑通过提高比沉淀值来改良面包烘烤品质.     

酸奶饮品稳定性影响因素研究

[目的]为了保证货架期内酸奶饮品的产品稳定性。[方法]以市面上畅销的酸奶饮品的平均离心沉淀率作为对照,研究生产工艺中重点因素对酸奶饮品稳定性的影响。[结果]在灭菌型酸奶饮品工业生产中,对产品稳定性影响最大的两个因素是稳定剂化料温度和均质工艺,提高化料温度并在基料奶发酵结束后增加1 次均质,可以极显著提高产品的稳定性。[结论]该结果将为乳品企业提高酸奶饮品稳定性提供有力的技术指导。