壳聚糖对细菌细胞膜的影响

研究了壳聚糖对大肠杆菌和金黄色葡萄球菌的抑菌性能。运用透射电子显微镜观察了壳聚糖作用前后大肠杆菌和金黄色葡萄球菌超微结构的变化;通过测定壳聚糖作用后菌液中OD260nm的变化,研究了壳聚糖对细菌细胞膜完整性的影响;通过测定壳聚糖作用后,菌悬液的上清液中所含壳聚糖残余量、乳酸脱氢酶和谷氨酰转移酶的内酶活性,考察了壳聚糖对细菌细胞外膜和内膜渗透性的影响。采用红外吸收光谱,对壳聚糖和模拟细胞膜卵磷脂间的反应产物进行表征。结果表明,壳聚糖可改变细胞内、外膜的渗透性而使细胞膜破坏,并伴随大量内溶物(DNA和mRNA)的溢出。壳聚糖与细胞膜间的作用主要是壳聚糖中的－NH3和卵磷脂中－C＝O、－P＝O形成了新的化合物引起的。     

Development and Evaluation of Whole-Cell Yeast Lactase for Use in Dairy Processing

A low-cost industrial grade lactase was developed for one-time use in dairy products. The preparation contained the entire biomass of a selected hyperproducing strain of the yeast Kluyveromyces fragilis. Intracellular lactase was made freely accessible to its substrate by permeabilization of the cell membrane with food compatible reagents. In 0.1M phosphate plus 0.4% methyl paraben, permeabilization was complete in 0.5–1 hr at 50°C, with 90% activity recovery from 180 g/L of cells. Whole-cell lactase contained no viable cells and was free of proteolytic activity. Its pH optimum of 5.6–6.0 proved suitable for lactose hydrolysis concurrent with cottage cheese fermentation. Hydrolyzed whey was used in ice cream and bakers' yeast production.     

Formation and Degradation of Beta-casomorphins in Dairy Processing

Milk proteins including casein are sources of peptides with bioactivity. One of these peptides is beta-casomorphin (BCM) which belongs to a group of opioid peptides formed from β-casein variants. Beta-casomorphin 7 (BCM7) has been demonstrated to be enzymatically released from the A1 or B β-casein variant. Epidemiological evidence suggests the peptide BCM 7 is a risk factor for development of human diseases, including increased risk of type 1 diabetes and cardiovascular diseases but this has not been thoroughly substantiated by research studies. High performance liquid chromatography coupled to UV-Vis and mass spectrometry detection as well as enzyme–linked immunosorbent assay (ELISA) has been used to analyze BCMs in dairy products. BCMs have been detected in raw cow's milk and human milk and a variety of commercial cheeses, but their presence has yet to be confirmed in commercial yoghurts. The finding that BCMs are present in cheese suggests they could also form in yoghurt, but be degraded during yoghurt processing. Whether BCMs do form in yoghurt and the amount of BCM forming or degrading at different processing steps needs further investigation and possibly will depend on the heat treatment and fermentation process used, but it remains an intriguing unknown.     

紫外技术在乳品加工中的应用

本文对紫外技术在乳品加工方面的应用进行了一些探讨,发现牛乳经紫外灯短暂照射后,可将杂菌总数由原来的1.2×10~7个/ml降至9.2×10~3个/ml,大肠菌群从9300个/100ml降至70个/100ml,牛乳中的维生素D从1.80 I·U/100ml提高到50.70 I·U/100ml,同时与热处理乳相比,其凝乳性状得到了提高。因此紫外照射技术在消毒乳,干酪等制品的加工中完全可替代传统的杀菌工艺,并得以广泛应用。另外也可以作为强化维生素D的一种新方法。     

乳品加工中的清洗消毒与保鲜技术

主要介绍了乳品加工企业每班必遇的原料乳保鲜、产前消毒、班后清洗与工作环境的杀菌消毒等技术措施。同时,还详细介绍了两种新型高效环保型的消毒剂在乳品加工业中的应用。     

不同干燥方式对细菌纤维素物理性能的影响

本文考察不同干燥方式对细菌纤维素的物理性能的影响。采取3种不同干燥的方法分别对细菌纤维素膜进行干燥,分别为:60℃烘箱中干燥(BC-DHT);在-20℃冷冻结实后冷冻干燥(BC-FDF);在液氮中迅速冷冻结实,然后冷冻干燥(BC-FDN)。通过扫描电子显微镜观察,BC-FDN的内部结构比BC-FDF和BC-DHT更松散。在吸水性能方面,BC-DHT、BC-FDF、BC-FDN每克纤维素吸水量分别为2.38 g、6.22 g、58.24 g。在透湿率方面,BC-FDN的透湿性能最好,其次为BC-FDF,而BC-DHT透湿性能最差。对BC-DHT、BC-FDF、BC-FDN进行X射线衍射分析,从其衍射图谱分析所得结晶指数分别为78.5%、64.2%、47.5%。热重分析结果分析所得,BC-DHT的热稳定性较好,其次为BC-FDF,而BC-FDN的热稳定性最差。由此可见,通过不同的干燥方法能改变细菌纤维素的物理性质。     

乳制品加工过程中热处理对营养成分的影响

乳制品生产过程中,热处理是一种经常用到的一种处理方法.不同的热处理温度,加热时间长短的不同均对乳中的营养成分有较大的影响.本文就乳制品生产中常见的热处理方式、不同热处理工艺对乳中营养成分的影响进行了综述,为乳制品的加工工艺的改进,提供一些有用的信息.     

Ultra-High Temperature Processing and Aseptic Packaging of Dairy Products

This status summary was prepared for participants in a National Workshop on Research Opportunities for the Dairy Foods Industry held in Berkeley, CA, November 1986. It presents brief discussions of regulations that influence progress in commercial manufacture of UHT products, equipment, and processes used in the US and elsewhere, changes in products during UHT processing and storage, some economic and consumer-related considerations, quality assurance for UHT products, and suggestions for future research.     

细菌纤维素/聚己内酯微米纤维复合膜的制备及性能

为制备模拟细胞外基质结构的微纳尺度复合材料,利用静电纺丝技术制备了聚己内酯(Polycaprolactone,PCL)微米纤维膜,通过与纳米尺度的细菌纤维素(Bacterial Cellulose,BC)原位复合,制备了BC/PCL复合纤维支架。采用扫描电镜、红外光谱分析、X射线衍射分析对材料的形貌、结构进行了表征。通过单轴力学测试对复合材料力学性能进行了研究,并利用成纤维细胞对复合材料的生物相容性进行评价。结果表明:通过静电纺丝法制备的PCL微米纤维的平均直径,随聚合物纺丝液质量分数的增加有增加的趋势,BC与PCL微米纤维复合后,BC纳米纤维渗透入微米纤维膜内部,实现微纳米纤维较好的复合。红外光谱分析和X射线衍射分析进一步证明BC和PCL微米纤维成功复合。PCL微米纤维膜复合BC膜后,相比PCL微米纤维膜增加了其断裂强度,同时复合支架无明显细胞毒性,可应用于生物医学领域。     

An Ecological Perspective of Listeria monocytogenes Biofilms in Food Processing Facilities

Listeria monocytogenes can enter the food chain at virtually any point. However, food processing environments seem to be of particular importance. From an ecological point of view, food processing facilities are microbial habitats that are constantly disturbed by cleaning and sanitizing procedures. Although L. monocytogenes is considered ubiquitous in nature, it is important to recognize that not all L. monocytogenes strains appear to be equally distributed; the distribution of the organism seems to be related to certain habitats. Currently, no direct evidence exists that L. monocytogenes-associated biofilms have played a role in food contamination or foodborne outbreaks, likely because biofilm isolation and identification are not part of an outbreak investigation, or the definition of biofilm is unclear. Because L. monocytogenes is known to colonize surfaces, we suggest that contamination patterns may be studied in the context of how biofilm formation is influenced by the environment within food processing facilities. In this review, direct and indirect epidemiological and phenotypic evidence of lineage-related biofilm formation capacity to specific ecological niches will be discussed. A critical view on the development of the biofilm concept, focused on the practical implications, strengths, and weaknesses of the current definitions also is discussed. The idea that biofilm formation may be an alternative surrogate for microbial fitness is proposed. Furthermore, current research on the influence of environmental factors on biofilm formation is discussed.     

乳制品消费与癌症风险控制

乳制品是营养价值很高的食物,但近年来对于乳制品的健康意义有了质疑之声。本文综述了乳制品与结肠癌、乳腺癌、前列腺癌、卵巢癌4种癌症发生风险关系的营养流行病学研究,对近年"牛奶致癌论"作出客观评价。证据表明,乳制品与前列腺癌和卵巢癌可能有一定的正相关性,但研究结果并不一致;乳制品对结肠癌的预防具有益处,对乳腺癌的影响未有定论;尚无证据表明每日摄入200g以下会显著增加癌症的风险。     

我国奶业区域发展研究

改革开放以来,我国奶业快速发展,其区域生产格局发生显著变化。本文分析了奶业区域布局演变,从品种、饲草饲料资源、经济条件等3方面分析影响奶业区域布局的形成,研究不同区域奶业发展重点,并提出相应的区域发展战略。     

白水回收及深处理自动控制系统的开发与研究

介绍了针对造纸白水回收的生产特点而研制的自动控制系统,其实际运行获得满意的控制效果。     

Effect of High-pressure CO2 Processing on Bacterial Spores

High-pressure CO₂ (HPCD) is a nonthermal technology that can effectively inactivate the vegetative forms of pathogenic and spoilage bacteria, yeasts, and molds at pressures less than 30 MPa and temperatures in the range of 20°C to 40°C. However, HPCD alone at moderate temperatures (20–40°C) is often insufficient to obtain a substantial reduction in bacterial spore counts because their structures are more complex than those of vegetative cells. In this review, we first thoroughly summarized and discussed the inactivation effect of HPCD treatment on bacterial spores. We then presented and discussed the kinetics by which bacterial spores are inactivated by HPCD treatment. We also summarized hypotheses drawn by different researchers to explain the mechanisms of spore inactivation by HPCD treatment. We then summarized the current research status and future challenges of spore inactivation by HPCD treatment.     

肉鸡屠宰加工中减菌处理前后细菌菌相分析

基于16S rDNA V6～V8可变区的聚合酶链式反应-变性梯度凝胶电泳（polymerase chain reaction-denaturinggradient gel electrophoresis,PCR-DGGE）技术分析肉鸡屠宰加工过程中减菌处理前后胴体或产品细菌多样性。在预冷环节前采用50 ℃、1.5%乳酸溶液对肉鸡胴体冲淋15 s进行减菌处理,采集屠宰加工环节中减菌处理前后的胴体或分割产品表面样品,提取样品中的细菌总DNA,通过16S rDNA V6～V8可变区的PCR扩增,变性梯度凝胶电泳,对PCR扩增片段割胶回收、克隆测序分析减菌前后细菌菌相变化。结果表明,减菌前,胴体清洗环节DGGE条带的数量最多、亮度最强,细菌污染最严重,其次是分割环节,而预冷环节细菌种类及数量最少,污染程度最低;减菌后,各屠宰加工环节细菌种类与数量较减菌前均有所减少,其中胴体清洗环节与分割环节细菌的种类与数量减少量最多,预冷环节细菌的种类及数量最少,不同屠宰加工环节细菌种类并不完全一致;乳杆菌属细菌在整个肉鸡屠宰加工过程中均有出现,与肠杆菌科和假单胞菌属细菌为肉鸡屠宰加工过程中的优势腐败菌。     

Genetic Control of Dairy Cattle Behavior

Past efforts to understand the genetics of behavior in cattle, and livestock in general, have emphasized changes related to the domestication process. Especially in intensive systems, domestic cattle may not express the full range of innate behavior when they are provided with food, shelter, and protection from predators. When provision of these necessities is inadequate or curtailed, a larger range of behaviors may occur. The goal of this paper is to explore the prospects of enhancing behavior genetically to better adapt dairy cattle to current and future dairy production systems. In dairy cattle, behavioral traits have been categorized as feeding, reproductive, maternal, social, learning, and human-animal interaction. Temperament, when scored subjectively and retrospectively by the human handler, is a measure of human-animal interaction. It is the most evaluated behavior trait in cattle, and is related to ease of handling, milking efficiency, and handler safety. Recent estimates of heritability for temperament range from 0.08 to 0.25, with differences observed among breeds. Thus, temperament may have potential for inclusion in breeding objectives. Traits that affect feeding behavior, such as time spent grazing and aggressiveness at the feed bunk in confinement systems, may prove to have great economic value. However, little is known about the genetic control of their expression. Duration and intensity of estrus behavior may be genetically influenced and is becoming increasingly important as labor for estrus detection becomes less available and more expensive. In the past, routine collection of behavior measurements has been difficult or impossible on a large scale. Future progeny-test programs or genetic improvement schemes, such as nucleus breeding herds using Multiple Ovulation and Embryo Transfer (MOET), that focus intensive data collection on a small number of large herds may foster recording of economically important behavioral traits like temperament, estrus expression, and measures of feeding behavior.     

功能性食品与功能性乳制品的开发

概述了功能性食品的定义,功能性食品的产生和发展,功能性食品的原料,并就中老年和婴幼儿功能性乳制品开发提出了指导性意见。     

细菌生物被膜检测与清除方法研究进展

开展食源性致病菌的防控研究以保障食品安全,具有显著的实践意义。作为细菌为适应不良环境所表现出的一种自我保护机制,食源性致病菌在食品生产加工过程中,可以黏附在食品原材料表面以及各种食品加工器械表面形成生物被膜,增大了消毒清洗的难度,给食品安全带来了严重的隐患和危害。因此,如何有效地清除细菌生物被膜成为食品安全领域的研究热点。结合细菌生物被膜形成过程和调控机制,本研究系统分析总结了细菌生物被膜的检测与清除方法的现状,为实现细菌生物被膜的有效控制,消除由生物被膜造成的食品安全隐患提供了综合性的认识,可为研究人员解决细菌生物被膜带来的食源性微生物污染提供参考,对保障食品安全有重要意义。     

生物有机肥对烟草青枯病的防效及对土壤细菌群落的影响

烟草青枯病是一种危害严重的土传性病害,为了防治烟草青枯病,筛选了3株拮抗青枯雷尔氏菌的芽孢杆菌（甲基营养型芽孢杆菌JK3、枯草芽孢杆菌JK4和解淀粉芽孢杆菌JK10）,将其发酵液添加到有机肥中,经二次发酵后获得生物有机肥（SF2、SF4）,施入烟田。结果表明,生物有机肥能较好地防治烟草青枯病,同时促进烟株的生长,SF2、SF4处理的防效分别为82.18%、68.82%。同时,采用高通量测序技术分析了土壤细菌的群落结构,发现生物有机肥显著影响了土壤细菌的群落结构,促进了土壤中有益菌（如鞘氨醇单胞菌属、类芽孢杆菌属、耐热芽孢杆菌、梭菌属等）的增殖。芽孢杆菌和链霉菌的数量也明显增加,推测链霉菌和芽孢杆菌可抑制青枯雷尔氏菌的繁殖,进而控制烟草青枯病的发生。施用添加拮抗芽孢杆菌的生物有机肥是防治烟草青枯病的一项有效措施。     

乳制品与糖尿病的饮食防控

本文综述了乳制品与糖尿病之间关系的研究进展。流行病学研究表明,乳制品对糖尿病的发生风险无不良影响,甚至有一定降低风险的作用。乳制品中的乳糖不会快速升高血糖,其反式脂肪成分并不是糖尿病的风险因子,而其中的乳清蛋白对于糖尿病患者是有利的。因此,乳制品是糖尿病患者饮食的有益组成。