Effectiveness of Sanitizing Agents in Inactivating Escherichia coli in Golden Delicious Apples

Research was undertaken to develop improved methods of sanitizing apples contaminated with Escherichia coli. Unwaxed Golden Delicious apples, inoculated with non pathogenic E. coli, were washed with 200 ppm Cl₂, commercial washing formulations, 5% H₂O₂, or combinations of H₂O₂ with commercial formulations at ca. 20°C or 50°C. Heated commercial formulations achieved a 2.5 log reduction in E. coli load, compared to a 2 log reduction for 200 ppm Cl₂. However, heated combinations of H₂O₂ with acidic surfactants achieved a 3–4 log reduction. Residual H₂O₂ in treated apples dissipated within several hours. These results demonstrate the efficacy of H₂O₂ in decontaminating apples containing E. coli.     

大肠杆菌转录调控因子oxyR与抗氧化基因ahpCF、katEG的协同作用

目的探讨大肠杆菌转录调控因子oxyR与抗氧化基因ahpCF、katEG在调控内源过氧化氢(H_2O_2)水平及生长繁殖中的作用。方法荧光法检测大肠杆菌内源H_2O_2,采用以氯化铈做特异染色剂的透射电子显微镜法和AR做染料的荧光分光光度法检测内源H_2O_2的数量变化。结果突变体菌株JI374中ahpCF基因的缺失导致内源H_2O_2积累减少,其生长速度显著提高。与此相反的是,katEG基因缺失的突变体菌株JI372和ahpCF、oxyR基因双突变菌株LC74中,内源H_2O_2水平上升,抑制了细菌的生长速率。结论 oxyR调控下的抗氧化体系相关基因不仅能够调控细菌内源H_2O_2水平,ahpCF、katEG与转录调控因子oxyR之间具有协同作用,共同调控细菌的生长代谢与繁殖。同时,在ahp基因缺失条件下,kat基因起主导作用;在oxyR、ahpCF、katEG基因的协同作用中,oxyR应起决定性的作用。     

净菜加工中常用的消毒杀菌剂

综述了净菜常用的消毒杀菌剂如卤素及卤素化合物、离子化合物质、有机酸、活性氧化合物等各自的优缺点。     

大肠杆菌抗氧化基因突变对内源过氧化氢的影响

为了阐明大肠杆菌(E.coli)抗氧化基因(ahp C/F、kat E/G、oxyR ahp C/F、sod A/B)对细菌内源过氧化氢(H2O2)调控中的协同作用,本研究以E.coli抗氧化基因突变株及其野生型菌株为研究对象,通过紫外分光光度法分析过氧化氢酶活性变化,荧光法检测内源H2O2浓度变化,组织化学法对细胞内H2O2进行定量和定位分析,光密度法分析菌株生长规律。结果表明,与野生型菌株相比,突变体JI367、JI370和AS240生长过程中过氧化氢酶活性总体升高,整个生长周期内H2O2浓度降低,而LC74过氧化氢酶活性降低,整个生长周期中内源H2O2浓度升高;组织化学染色法表明各菌株内源H2O2有显著差异(p<0.05),LC74内源H2O2累积量最多;JI367、JI370和AS240生长迟缓,LC74对数期后期生长速度较野生型快。结果说明,当H2O2浓度累积到高于大约5.4μmol/L时促进E.coli生长,不同的抗氧化基因之间受调控子蛋白OxyR调控存在补偿性表达作用,抗氧化酶Ahp C/F在降解内源H2O2方面起主要作用。本实验为细菌内源H2O2的调控机制的系统研究提供了新的证据。      

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.     

活性染色的氧化清洗工艺

采用尿素/H₂O₂活化体系对纤维表面的活性染料浮色进行氧化清洗,探讨尿素/H₂O₂配比、氧化清洗温度、时间、pH值等条件对活性染料氧化清洗效果的影响。结果表明,活化体系采用尿素3.84g/L,27%H₂O₂ 2.25mL/L,pH值9,氧化清洗温度85℃,时间8min,具有较好的清洗效果,各项牢度指标与常规皂洗工艺相当,且氧化清洗减少了水洗次数,降低了能耗。     

Microbiological Decontamination of Poultry Feed—Evaluation of Steam Conditioners

The microbial decontamination of chicken feed, obtained from a commercial pellet mill, was evaluated using a direct-fired steam conditioner (DFSC; APC System^™). The standard plate count of the feeds before (mash) and after (pellets) conditioning ranged from 65×10⁴ to 83×10⁵ colony forming units (CFU) g⁻¹ and from 91×10¹ to 92×10³ CFU g⁻¹, respectively. The incidence of Escherichia coli , Salmonella and Listeria in the feeds before conditioning was 61·7, 8·3 and 27·1%, respectively. Following conditioning these levels were reduced to 1·7, 1·7 and 0%, respectively. Species of Listeria and Salmonella identified included L monocytogenes , L innocua and S agona , S ohio , S heidelberg , S senftenberg , S tallahasse and S braenderup , respectively. Compared with a conventional, indirect-fired boiler-generated-steam conditioner (IFSC) the direct-fired steam conditioner proved superior in regards to pathogen decontamination; no E coli , Salmonella or Listeria were recovered from mash lots positive for these microorganisms. However, with the IFSC system, both E coli and L monocytogens were recovered at levels of 11·1 and 5·6%, respectively.     

Effect of gaseous ozone on microbial inactivation and sensory of flaked red peppers

Flaked red peppers inoculated with Escherichia coli , Bacillus cereus and B. cereus spores were exposed to gaseous ozone at 20 °C and 70% relative humidity (RH). Ozone concentrations of 0.1, 0.5 and 1.0 ppm up to 360 min were used to reduce E. coli and B. cereus, whereas 1.0, 5.0, 7.0 and 9.0 ppm ozone concentrations for 360 min were used to treat B. cereus spores. When flaked red peppers were treated with 1.0 ppm ozone concentration for 360 min, B. cereus and E. coli counts were decreased by 1.5 and 2.0 log numbers, respectively. Bacillus cereus spores were reduced by 1.5 log numbers at ozone concentrations of 7.0 ppm or above for 360 min. There were slight changes in flavour, appearance and overall palatability of flaked red peppers treated with ozone between 5.0 and 9.0 ppm. Ozone concentration (1.0 ppm) for 360 min can be used to decrease E. coli and B. cereus, whereas ozone concentrations ≥5.0 ppm can be used to reduce B. cereus spores.     

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.     

废油脂生物柴油的脱硫处理研究

液体燃料的硫排放是环境污染的一个重要来源。废油脂制得的生物柴油硫含量往往超出国家标准。在相同条件下,采用活性炭、阴离子交换树脂、活性白土3种吸附剂对地沟油生物柴油进行脱硫试验。结果表明:活性炭脱硫效果较好,在活性炭用量为地沟油生物柴油质量的3%、吸附温度65℃、吸附时间30 min条件下,生物柴油脱硫率为11.7%。试验发现地沟油生物柴油采用双氧水洗涤后再进行二次负压蒸馏能达到显著的脱硫效果,生物柴油脱硫率达77.8%;高含硫地沟油、棕榈酸化油制备的生物柴油最佳的脱硫工艺为原料油经双氧水洗涤、生物柴油粗品二次负压蒸馏,生物柴油成品脱硫率分别达到95.6%、93.3%,硫含量分别为6.7、8.9 mg/kg,满足国Ⅵ柴油排放标准(GB 19147—2016)的硫含量小于等于10 mg/kg要求。     

Assessing the effects of incorporating bubbles into the water used for cleaning operations relevant to the food industry

These studies examined the effects of incorporating bubbles of air in the water used for cleaning surfaces. Small (<50 μm) or large (millimetre) bubbles were used, and these could aid cleaning by a scrubbing action, energy release or free radical production. Small or large bubbles improved the removal of biofilm from steel surfaces by 1.0 log₁₀ or 1.6 log₁₀, respectively. Biofilm removal from a polypropylene pipe wall was improved by 0.9 log₁₀ by incorporating bubbles into the cleaning water. Further trials showed increased removal of carbohydrate, fat and protein deposits from stainless steel by incorporating bubbles into the water. These results suggest that the use of air bubbles in water could provide small improvements in cleaning or potentially similar contamination removal using less water.