Proteomic analysis of responses of a new probiotic bacterium Lactobacillus casei Zhang to low acid stress

Tolerance to acid is an important feature for probiotic bacteria during transition through the gastrointestinal tract. Proteomics analysis of a new probiotic bacterium, Lactobacillus casei Zhang, was performed upon 30-min exposure to low acid stress (pH 2.5 vs. pH 6.4) using two-dimensional electrophoresis. Out of 33 protein spots that showed changes of expression between the two pHs, 22 showed 1.5-fold higher expression at pH 2.5 than at pH 6.4, whereas five spots had expression decreased by 1.5-fold at pH 2.5. There were also six protein spots that were exclusively present on different pH maps. Further analysis showed that eight of the enhanced proteins, NagA, NagB, PGM, GlmM, LacC, TDP, GALM and PtsI, were involved in carbohydrate catabolism. Moreover, quantitative RT-PCR showed that the mRNA expression levels of dnaK, nagB, galm, estC, tuf and luxS were consistent with changes in protein expression. We postulate that there might be some relationship between differentially expressed proteins and acid tolerance in L. casei Zhang.     

冷却牛肉贮藏过程中的品质变化

分析冷却牛肉贮藏过程中各品质指标的变化,确定理化指标和微生物指标的相关性,为提高牛肉的品质提供依据。文中测定了4℃贮藏的冷却牛肉在0、2、4、6、8、10、12、14 d的菌落总数、嗜冷菌总数、pH值、挥发性盐基氮、失水率、色差值,确定了各指标随保存时间的变化规律及其相关性。结果表明:在贮藏过程中,pH值呈现先下降后上升的趋势;挥发性盐基氮呈上升趋势;系水力逐渐下降;肉色a值、DE(d ifference error)值不断降低。在品质变化的各指标中,微生物菌落总数、嗜冷菌总数与pH值呈正相关,且差异显著(P<0.05);菌落总数与系水力、a值呈负相关性,差异显著(P<0.05)。其中菌落总数与挥发性盐基氮、a值的相关性较大且极显著相关(P<0.01)。由此可知,微生物的活动能引起牛肉理化指标的变化,通过测定挥发性盐基氮和a值可以客观反映冷却牛肉的微生物污染状况。     

瓜拉纳抗疲劳功效的研究

雄性昆明小鼠按体重随机分为3组(I-瓜拉纳、II-西洋参液、III-纯水对照)。每组小鼠每日分别一次性灌服剂量20mL/kg,连续灌胃35d后,进行耗竭性游泳实验,测定小鼠游泳时间,运动后全血乳酸水平、血清尿素氮水平及肝糖原含量。结果表明:与纯水相比,瓜拉纳、西洋参可显著降低雄性小鼠体内的血乳酸水平,其中瓜拉纳还能显著提高雄性小鼠体内的肝糖原储备。     

红枣醋醋酸发酵工艺条件的优化

以北京郎家园枣为原料,结合现代发酵技术进行酿醋。首先对发酵方式进行选择,试验发现摇床发酵结果好于静置发酵。针对摇床发酵过程中摇床的转速、醋酸菌的接种量、发酵温度和初始酒精含量对发酵结果有影响,故采用单因素试验和响应面试验,寻找发酵最佳工艺条件,通过matlab软件对数据进行分析,研究得出最佳条件为:初始酒精含量6%、接种量5%、摇床转速160 r/min、发酵温度32℃。     

贮藏过程中冷却牛肉微生物模型的建立

冷却牛肉贮藏过程中易受微生物的污染,通过建立微生物数学模型,可以预测冷却牛肉的污染情况。实验以自然污染下的冷却牛肉为介质,对0、4、7、10、15、20℃恒温条件下的菌落总数进行计数,利用SAS软件拟合Modified Compertz方程,并对比生长率和时间拟合了平方根二级模型,最后在波动温度下对模型进行了验证。结果显示,Modified Compertz方程能很好地反映冷却牛肉中菌落总数的污染情况,恒定温度下的模型拟合度都在0.95以上,对波动温度条件下的菌落总数的预测值与实测值进行比较,偏差度为0.90,准确度为1.12,表明菌落总数生长模型可以可靠地预测冷却牛肉的微生物污染情况。     

乳清分离蛋白-可溶性淀粉接枝物的制备及其理化性质

研究了干热法处理条件下乳清分离蛋白-可溶性淀粉接枝物的制备及其二级结构分析,为蛋白质-淀粉接枝物的研究提供参考。A294、褐变、游离氨基含量变化、电泳图谱等证实乳清分离蛋白与可溶性淀粉在干热处理下确实发生了以美拉德反应为基础的接枝反应,且反应天数的延长能够显著促进乳清分离蛋白-可溶性淀粉接枝物的生成。由于大分子淀粉的共价接入,乳清分离蛋白的二级结构遭到破坏;蛋白质表面疏水性指数降低。     

Effects of phytase,cellulase and dehulling treatments on zinc in vitro solubility in faba bean (Vicia faba L.) flour and seed fractions

Simulations of gastro‐intestinal digestion was used to try to identify the nature of the complexes between antinutritional factors and zinc in faba bean fractions. In the hull fraction, the action of phytases and the simultaneous action of cellulase and phytase allowed about 7% and 35% additional zinc to be solubilised, respectively. Single enzymatic degradation of phytates from dehulled faba bean allowed solubilisation from 65% to 93% of zinc depending upon the treatment. The zinc of faba bean flour was mainly linked to phytates and the greater the degree of phytate degradation before in vitro digestion, the greater the quantity of zinc released. In dehulled faba bean zinc was almost exclusively chelated by phytates. In the hull of faba bean, the majority of zinc was chelated in complexes between phytates and fibres.     

喷淋淀粉混合物改善双层纸板的层间结合强度

工厂将天然淀粉液喷淋到成形的湿纸幅上以改善多层纸板的层间结合强度。文中研究了回收针叶木硫酸盐浆手抄片湿纸幅干度、淀粉液喷淋量及干燥温度对双层纸板层间结合强度的影响。淀粉喷淋到湿纸幅上可以大幅度提高湿纸板的层间结合强度。湿纸幅干度在10％-11％左右时,强度达到最大。针对高温快速干燥影响淀粉的胶凝化作用,降低纸板的层间结合强度,提出了一种高干燥速率下提高纸板层间结合强度的方法,实现淀粉逐步胶凝化,大大提高纸板层间结合强度。     

驴肉主要营养成分及与其它畜禽肉的分析比较

本文测定了驴肉的水分、灰分、蛋白质、粗脂肪、脂肪酸、矿物元素、氨基酸的含量,并将驴肉与其他畜禽肉的营养成分作对比分析。结果表明:驴肉蛋白质含量比羊肉、牛肉、猪肉高,而脂肪含量比羊肉、牛肉、猪肉低。驴肉的氨基酸和脂肪酸组成是比较理想的,矿物元素中Fe含量明显高于其它畜禽肉。从营养学角度看,驴肉是比较理想的动物性食品原料。