Streptomyces olivaceovirdis E-86木聚糖酶在玉米芯成分上吸附特性的研究

研究了在4℃条件下,由橄榄灰绿链霉菌(StreptomycesolivaceovirdisE-86简称sp.E-86)产木聚糖酶分别在木质纤维玉米芯成分:纤维素、木聚糖、木质素、全纤维素和玉米芯粉上的吸附动力学以及吸附90min时的吸附等温线。结果表明,该木聚糖酶在这些木质纤维上很快达到平衡,除木聚糖在1h达到平衡外,其它都不超过30min;吸附等温线都符合两阶段非均匀表面吸附模型;在所有吸附等温线中,玉米芯吸附量最大,纤维素最小;在三种纤维中,全纤维素吸附量最大、木聚糖次之、纤维素最小。     

Keeping quality of tomato fruit by high electrostatic field pretreatment during storage

BACKGROUND: High electrostatic field, as a feasible and non‐chemical technique, applied to food preservation is a new area of study. The present article intensively investigated this new preservation method, together with its effects on post‐harvest physiology and quality of tomato. RESULTS: Green mature tomatoes were exposed to negative (or positive) high electrostatic field for 2 h at 20 °C and then stored for 30 days at 13 ± 1 °C, 85–90% RH. Our results indicated that negative high electrostatic field (?2 kV cm^?1) could delay the decline of firmness and the change in color, total soluble sugar and titratable acidity of tomato fruit during storage. The peak of respiration and ethylene production of tomato fruit during storage were delayed by negative high electrostatic field treatment for 6 days and 3 days, respectively. Increases of malondialdehyde content and electrical conductivity in tomato fruit were inhibited significantly by negative high electrostatic field treatment during storage (P < 0.05). CONCLUSION: A high electrostatic field of ? 2 kV cm^?1 can be used to keep the qualities and extend the shelf‐life of tomato fruit. Further research should be highly recommended to understand the mechanisms improving the storability of tomato fruit by negative high electrostatic field. Copyright © 2007 Society of Chemical Industry     

预测微生物学的研究进展

预测微生物学是基于微生物的数量对于环境的响应是可以重现的 ,通过有关环境因素的信息就可以从过去的观测中预测目前食品中微生物的数量。预测微生物学的研究对食品微生物学具有重要应用价值。国际上对此产生浓厚的兴趣 ,欧盟自 1989年将其列入相关的研究计划并持续进行。文章中回顾了预测微生物学的发展历程 ,介绍了目前的发展状况、主要研究内容、方法、用途以及今后的发展方向。尽管许多食品体系具有复杂性 ,但预测模型能够简化问题 ,从而做出有用的预测分析     

方便鲜米粉加工技术的研究

本文对方便鲜米粉的加工技术进行了试验研究。为了生产方便性好的米粉,对方便鲜米粉的加工技术进行了探讨。通过大量试验,确定了方便鲜米粉的加工方法、使用原料和老化条件。     

2种蛋白酶的大豆蛋白水解物对血管紧张素转换酶的抑制作用

报道了 2种工业化酶ProteaseA和OrientaseB的大豆蛋白水解物的高活性ACEI肽的筛选工作 ,并且对所得到的活性较高的水解物进行了感官评价。这 2种酶的水解物的ACE抑制活性均随着水解时间的增加呈指数归律增加。其中OrientaseB水解大豆蛋白 1 0h ,其产物的ACE抑制活性最高达到 95 %,ProteaseA的最高也可达到 91 33%。ProteaseA水解 4～ 1 0h的产物以及Ori entaseB水解 6～ 1 0h的产物 ,是由 2～ 5个氨基酸组成的寡肽 ,ACE的抑制活性高 ,且苦味轻微或没有。这些肽因其天然、安全、作用温和而有望作为良好的降压成分进入人们的日常膳食。     

乳酸菌发酵改善米粉食用品质的机理

以早籼稻为原料 ,研究了以乳酸菌发酵改善大米淀粉凝胶食用品质的机理 ,揭示了大米淀粉的功能性与结构之间的关系。GPC结果表明 ,淀粉颗粒经过凝胶柱被分成 2部分(FrⅠ ,FrⅡ ) ,FrⅠ区为支链淀粉 ,FrⅡ区为直链淀粉。乳酸菌发酵使大米中的支链淀粉的平均聚合度由 12 6 76 3GLU降低到 115 0 0 4GLU ,而直链淀粉的平均聚合度由 2 975 3GLU增加到 35 6 3 2GLU ;支链淀粉的平均链长由 6 1 2GLU下降到 4 5 0GLU ,直链淀粉的平均链长由 2 3 7GLU增加到 2 8 4GLU ;直链淀粉的含量由 12 33%增加到 17 37% ;蛋白质含量由6 89%下降到 4 2 0 %。拉伸试验证明 ,乳酸菌发酵使米粉的最大破短应力显著增强 ( p <0 0 1) ,伸展率 /断面收缩率及最大破短应变显著增加 ( p <0 0 1) ,杨氏模量显著下降 (p <0 0 1) ,经感官评定 ,米粉筋道柔韧。     

后发酵过程中乙醇对豆豉抗氧化能力的影响

以黄豆为原材料,接种米曲霉制作豆豉,在豆豉后发酵过程中设定了不同乙醇添加量,测定了不同乙醇添加量的豆豉样品清除DPPH(2,2-diphenyl-1-picrylhydrazyl hydrate)及ABTS[2,2-’azinobis-(3-ethylbenzthia-zoline-6-sulfonic acid)]自由基能力、Fe2+螯合能力、还原能力,评价了乙醇对豆豉抗氧化能力的影响。后发酵过程中,豆豉的抗氧化能力持续增大,醇对豆豉的抗氧化能力有影响,发酵相同时间的豆豉,抗氧化能力随乙醇含量的增大而下降。     

密封式谐波齿轮减速器柔轮的实验应力分析

对密封式谐波齿轮减速器的柔轮进行实验应力分析。得出了柔轮在装配状态及不同工作扭矩T作用下，沿轴向各截面的应力分布情况，确定了危险截面的位置，为密封式柔轮的结构参数和尺寸的确定提供了有价值的实验数据。     

Physicochemical Properties, Firmness, and Nanostructures of Sodium Carbonate-Soluble Pectin of 2 Chinese Cherry Cultivars at 2 Ripening Stages

ABSTRACT:  Firmness and physicochemical properties of 2 Chinese cherry ( Prunus pseudocerasus L.) cultivars (soft cultivar "Caode" and crisp cultivar "Bende") at unripe and ripe stages were investigated, and the qualitative and quantitative information about sodium carbonate-soluble pectin (SSP) nanostructures was determined by atomic force microscopy (AFM). The lengths and widths of the cherry SSPs are very regular: almost all of the widths and lengths of SSP single molecules are composed of several basic units. The widths of the SSP chains are 37, 47, 55, and 61 nm, and the lengths are 123, 202, and 380 nm in both cultivars. The results show that the firmer cherry groups (crisp fruit) contain more percentages of wide and short SSP chains than soft fruit, and the unripe groups contain more percentages of wide and long SSP chains than corresponding ripe groups. They indicate that those nanostructural characteristics of SSP are closely related with firmness of the Chinese cherries in each cultivar.