染整工艺变量pH和ORP的在线测控

论述了染整、工艺变量酸碱值pH及双氧水氧化还源电位差法测定氧化值所涉及的仪表、系统的组成、机理。列举了有关应用例案,     

用ORP监控鲜切果蔬臭氧水消毒的实验研究

研究了用氧化还原电位(ORP)监控臭氧水对鲜切果蔬的消毒灭菌过程,通过不同ORP的臭氧水消毒实验发现,将鲜切果蔬浸入ORP超过800mV的臭氧水中超过30s可以使细菌总数下降约2个数量级。通过改变臭氧浓度和水温的方法研究了臭氧水ORP的影响因素,得出了提高臭氧气体浓度和低温制冷有利于制取高ORP臭氧水的结论。结果表明,利用ORP监测臭氧水的消毒能力是可行的。      

用ORP监控鲜切果蔬臭氧水消毒的实验研究

研究了用氧化还原电位(ORP)监控臭氧水对鲜切果蔬的消毒灭菌过程,通过不同ORP的臭氧水消毒实验发现,将鲜切果蔬浸入ORP超过800mV的臭氧水中超过30s可以使细菌总数下降约2个数量级。通过改变臭氧浓度和水温的方法研究了臭氧水ORP的影响因素,得出了提高臭氧气体浓度和低温制冷有利于制取高ORP臭氧水的结论。结果表明,利用ORP监测臭氧水的消毒能力是可行的。     

烤烟水溶液pH值分析方法研究

由于目前烟草行业尚没有测试烟叶pH值的标准方法,同一种烟叶样品,测试方法不同,其pH值的测定结果就可能不同,这就给客观评价烟叶质量带来较多困难。为了确定测定烟叶pH值的适宜条件,通过2d跟踪测试烤烟水浸液pH值的变化,考察了蒸馏水pH值、存放气氛、实验室温度和测试时间对烟叶pH值测试结果的影响。结果显示,蒸馏水的pH值和存放气氛对烟叶pH值的测试结果无显著性影响,实验室温度对烟叶pH值的测试结果影响较大。温度较高时,影响较显著,25℃下烤烟pH值在初始测试的1h内降低了5.2%,第二天测试pH值的下降速度变缓,且与测试时间呈良好的线性关系,其线性相关系数的平方(R2)等于0.9961;12℃下,除在0～10min内pH值略有升高外,总体上是pH值随着测试时间的延长呈极为缓慢的降低趋势。此外,还采用实验确定的适宜条件即普通蒸馏水浸提、敞口存放、第二天读数的方法测定了我国一些主要烤烟产区2种复烤叶片———B2F和C3F的pH值。     

食用盐水溶液pH值的测定

为了消除碘缺乏病 ,使加入食用盐中的碘更加稳定 ,让全国人民吃到合格的碘盐 ,有些生产厂采取加入碱性物质使盐 ｐＨ值控制在一定范围。本方法探讨了食用盐水溶液ｐＨ值的测定 ,更好地指导生产。1　试验方法1 1　原理用电位法测定食用盐水溶液 ｐＨ值 ,是以玻璃电极作指示电剂 ,饱和甘汞电极作参比电报。1 2　仪器、设备1 2 1　ＰＨＳ - 3Ｃ型酸度计或其它型号的酸度计 ,测量范围 0～ 14ｐＨ ,分度值为 0 1ｐＨ单位。1 2 2　指示电极 :玻璃电极。1 2 3　参比电极 :饱和甘汞电极。1 2 4　实验用玻璃水银温度计。1 3　试剂和溶液本方法所…     

瓶、桶装水工业的O3技术

迅速发展的瓶,桶装水工业,促进了Ｏ３工艺的发展,本文对Ｏ３即臭氧的特性,Ｏ３工艺以及Ｏ３在饮用水中运用进行阐述,从而生产出高质量的产品。     

瓶、桶装水工业的0_3技术

迅速发展的瓶、桶装水工业,促进了０_３工艺的发展。本文对Ｏ_３即臭氧的特性、Ｏ_３工艺以及Ｏ_３在饮用水中运用进行阐述,从而生产出高质量的产品。     

黑曲霉耐臭氧能力的研究

霉菌是果蔬保鲜过程中,特别是在湿冷系统中常见的一种致腐烂性微生物。本文以黑曲霉为研究对象,在黑曲霉菌液中通入臭氧,观察黑曲霉耐臭氧的能力。      

黑曲霉耐臭氧能力的研究

霉菌是果蔬保鲜过程中,特别是在湿冷系统中常见的一种致腐烂性微生物。本文以黑曲霉为研究对象,在黑曲霉菌液中通入臭氧,观察黑曲霉耐臭氧的能力。     

臭氧漂的选择性及其改善

臭氧漂白的最大缺陷在于其选择性差,而这很大程度是由于漂白过程中产生了选择性差的HO·自由基。本文介绍了臭氧漂白过程中自由基的产生及如何加以控制以达到改善、提高臭氧漂白选择性的目的。     

pH值对大肠杆菌发酵异亮氨酸的影响

以L-异亮氨酸生产菌E.coli TRFP为出发菌株,考察不同pH值对发酵过程中重组酶酶活、菌体生物量、L-异亮氨酸产量和葡萄糖消耗速率以及副产物积累等方面的影响。研究表明:与恒定pH 7.2控制策略相比,采用分段控制pH值的工艺可使最大生物量和异亮氨酸产量分别提高了6.1%和9.2%,乙酸及NH4+浓度分别减少7.8%和11.6%;同时,采用NaOH和氨水混合碱调节pH值能够有效降低NH4+对菌体的抑制作用,减缓菌体衰退。     

Effectiveness of ozone for inactivation of Escherichia coli and Bacillus cereus in pistachios

The effectiveness of ozone for the decontamination of Escherichia coli and Bacillus cereus in kernels, shelled and ground pistachios was investigated. Pistachios were inoculated with known concentrations of E. coli and B. cereus. Pistachio samples were exposed to gaseous ozone in a chamber at three different concentrations (0.1, 0.5 and 1.0 ppm) for various times (0–360 min) at 20 °C and 70% relative humidity. The effectiveness of ozone against E. coli and B. cereus increased with increasing exposure time and ozone concentration. The physico‐chemical properties including: pH, free fatty acids and peroxide values, colour and fatty acid composition of pistachios did not change significantly after the ozonation treatments, except for the peroxide value of ground pistachios ozonized at 1.0 ppm for 360 min. Ozone concentration of 1.0 ppm was effective in reducing E. coli and B. cereus counts in kernels and shelled pistachios, while ozone concentrations <1.0 ppm were found to be appropriate in reducing the number of both bacteria in ground pistachios without having any change in their physico‐chemical properties.     

随瓶,桶装水工业发展而发展的O3工艺

介绍了臭氧的特性及适合于瓶,桶装水的臭氧工艺,对Ｏ３在饮用水生产中的控制形式进行了阐述,以期生产出口感好,贮期长的产品。     

酱油等调味品中大肠杆菌存活与分析

分析大肠杆菌在酱油中的存活特性,为酱油等调味品的卫生控制和检测提供技术指导。将购置的标准大肠杆菌菌株和从酱料中分离的野生型大肠杆菌人工接到大肠杆菌阴性的不同品种和厂家的瓶装酱油中,采用国家标准方法定期检测大肠杆菌的个数,计算大肠杆菌的存活时间,对大肠杆菌在不同品种和不同厂家酱油中的时间的存活率进行了研究。结果表明,不同种类大肠杆菌在酱油中存活时间不同,同种大肠杆菌在老抽系列酱油中的存活时间长于在生抽酱油的存活时间,时间长2 d~4 d,而在生抽中存活时间为1 d,存活时间短于以前的报道。同时普查了大肠杆菌在国内其他厂家酱油中的存活时间,发现存活时间多为1 d~2 d,并且不同种类存活时间存在差异。大肠杆菌在酱油中致死现象和机制有待进一步分析,该研究为当前控制酱油中大肠杆菌的污染问题提出了新的证据和启示。     

荧光光度法快速定量大肠杆菌的实验方法研究

研究比较了菌体渗透处理方式与培养方式对大肠杆菌荧光光度法检测效果的影响,以及考察了培养条件对荧光强度的影响,结果表明仅采用渗透处理方式处理菌液会造成荧光检测值偏小,灵敏度偏低;但经LST-MUG（pH7.0）培养液44℃培养7h后的荧光值能对100.9～106.8cells/mL范围内的大肠杆菌进行定量,结果与国标方法无显著性差异。该法进一步缩短了大肠杆菌的检测时间至8h左右,且重现性良好,适合于大肠杆菌的定量检测。     

Detection of Escherichia coli O157 in bovine meat products in northern Italy

Tests for Escherichia coli and E. coli O157 were carried out on meat samples collected from randomly chosen stores throughout the city of Bologna and suburban areas. The samples consisted of 25 g of loose minced beef, sometimes already shaped into meatballs or hamburgers, some of which were mixed with vegetables. The meat was purchased from retail outlets, open market stalls, and supermarket chains during 25 sampling visits from October 2000 to December 2001. For E. coli detection, Tryptone soya broth (TSB) supplemented with novobiocin and C-EC agar were used. Immunomagnetic separation with SMAC-BCIG-CT agar and chromogenic E. coli O 157 agar, API 20E system and agglutination latex test were used to detect E. coli O157; Vero cell assay and polymerase chain reaction (PCR) were used to assess toxin production and the presence of virulence genes.

E. coli were detected in 45 (30.2%) of the 149 samples examined, mainly in the hamburger samples mixed with vegetables and in the loose minced beef. E. coli O157 was found in one sample of hamburger and two samples of hamburger mixed with vegetables (2%) collected from three different butcher's stores between July and October. All the strains of E. coli O157 and most cases of E. coli were found in meat from small retailers.

The three strains of E. coli O157 were positive for verocytotoxin production. PCR analysis revealed genes coding for vt2 and one strain possessed the gene for eae A. Chromogenic E. coli O157 agar was found to be more selective and differential, allowing easier identification of suspected colonies with mixed flora and producing less false-positive colonies.     

The epidemiology,detection and control of Escherichia coli O157

Numbers of cases of human infections caused by Escherichia coli O157 have increased over the last decade in many countries. As well as the typical symptoms of gastrointestinal illness, the organism can cause more life-threatening diseases such as haemorrhagic colitis and haemolytic uraemic syndrome (HUS). Although the incidence remains relatively low compared with the other foodborne pathogens such as Campylobacter and Salmonella, the mortality rate associated with infection is much higher. Cattle are thought to be the main environmental source of this organism, and most cases have been associated with consumption of beef and beef products. However, other food vehicles have been identified, such as apple cider and raw or unpasteurised milk and milk products. Cross-contamination has been shown to be an important factor in outbreaks, which, together with the fact that the infectious dose is low (as few as 10 cells), means that robust hygienic procedures are essential at all stages of the food chain to reduce risk of infection. Person-to-person spread is a common source of illness, and several laboratory-acquired cases have also occurred. Efficient detection, isolation and confirmation techniques are required to establish the reservoirs of this organism in the environment and its spread into, and within, the food chain. This article reviews the epidemiology of E coli O157 and discusses detection and preventative methods, both developed and developing. © 1999 Society of Chemical Industry     

固定化重组大肠杆菌产1,3-丙二醇发酵条件的研究

利用海藻酸钙将重组大肠杆菌JM109(pHsh-dhaB-dhaG-dhaF-yqhD)固定化,并对影响重组菌固定化细胞发酵的营养因子进行研究。实验结果表明,该重组菌固定化细胞发酵的适宜培养基组成为:甘油80 g/L、酵母膏5.0 g/L、VB120.05 g/L以及KH2PO47.5 g/L;在此培养条件下,1,3-丙二醇产量、转化率及生产能力分别可达61.5 g/L、76.8%和2.57 g(L.h),与游离细胞相比,重组菌固定化细胞对底物甘油和产物1,3-丙二醇的耐受力明显提高,且1,3-丙二醇产量明显提高。     

高强脉冲电场对食品中大肠埃希氏菌基因水平传递的影响

目的:探讨高强脉冲电场对大肠埃希氏菌的基因获得及水平传递中的作用。方法:采用接合转移试验,研究了PEF强电场作用对大肠埃希氏菌基因水平传递的影响,并以未经处理的标准菌株为对照,通过PCR方法进行基因检测分析。结果:所有经PEF处理的菌株均由正常的接合转移率42.4%～68.5%上升到100%。PCR检测结果显示,所得接合子中int基因的扩增产物大小仍为923bp,与正常未处理int基因大小一致。结论:PEF处理使得细菌接合转移率明显提高,PEF处理对传递到接合子中的基因未能产生影响。     

食品中大肠杆菌的快速检测方法

大肠杆菌是人及各种动物肠道中的正常寄居菌,食物或水中大肠杆菌的检出意味着直接或间接的近期粪便污染。大肠杆菌作为饮水、食品等的粪源性污染卫生细菌学指标;而且他在外界存活时间与一些主要肠道病原菌相近,它的出现也可能预示某些肠道病原菌（如沙门氏菌、志贺氏菌）的存在。大肠杆菌是国际上公认的卫生监测指示菌,因此大肠杆菌的检测技术显得十分重要,相应出现了大量的大肠杆菌的各种检测方法。