姜黄素介导的光动力技术对鲜切马铃薯的杀菌效果

本文运用光动力技术（Photodynamic technology,PDT）对鲜切马铃薯进行非热杀菌,实验选用姜黄素为光敏剂,420 nm LED蓝光为激发光源。探究了光照功率、光照时间、孵育时间以及光敏剂浓度等因素对鲜切马铃薯表面大肠杆菌、金黄色葡萄球菌杀菌效果的影响,并确定最优杀菌条件。结果表明,该技术对大肠杆菌的最优杀菌条件分别为:光照功率40 W、光照时间20 min、孵育时间15 min、姜黄素浓度30 μmol/L;金黄色葡萄球菌的最佳杀菌条件分别为:光照功率40 W、光照时间10 min、孵育时间15 min、姜素浓度30 μmol/L。与对照组相比,光动力技术处理后的大肠杆菌与金黄色葡萄球菌菌落总数分别为降低3.60与5.23 lg CFU/mL。     

超声非热处理因素对细菌杀菌效果的影响

本文以大肠杆菌和金黄色葡萄球菌这两种食品中常见的污染菌为研究对象,考察了超声处理条件、介质、温度对超声非热杀菌效果的影响。结果表明:超声处理对大肠杆菌有较强的杀菌作用,金黄色葡萄球菌则对超声非热处理有很强的抵抗力;超声强度增大、作用时间延长、温度升高都有利于杀菌效果的提高;在培养基介质中的杀菌效果强于蒸馏水介质中的情况。结果分析认为,有利于空化作用提高或使细胞强度变弱的条件都有利于提高杀菌效果。冷藏结果表明,杀菌处理后的细菌没有出现复活生长的迹象。     

一种提高液态食品中金黄色葡萄球菌检出限的方法

目的:研究出一种可以富集液态食品中金黄色葡萄球菌,提高金黄色葡萄球菌检出限的样品处理方法,用于液态食品中金黄色葡萄球菌的快速检测。方法:通过对样品取样量、易起泡样品消泡方法的研究,离心时间的选择、微孔滤膜材质和孔径的选择、滤膜洗脱液的选择、洗脱方式的选择等,确定最佳样品富集处理方法,并将该方法与国标方法进行对比验证试验,确定其有效性和准确性。结果:最佳技术路线为最大取样量500 mL,10 mL消泡剂聚二甲基硅氧烷(PMX)消泡预处理,无菌条件下20℃8000 r/min离心6 min后,用Φ50 mm 0.45μm聚醚PES微孔滤膜抽滤,再用10 mL Hanks平衡盐溶液洗脱浸泡,震荡2 min,所得溶液即为样品待测浓缩液。结论:建立了最佳的富集金黄色葡萄球菌的条件和样品处理方法,使液态食品中金黄色葡萄球菌的检出限和灵敏度显著提高。     

姜黄素介导的光动力冷杀菌技术在食品中的研究进展

姜黄素介导的光动力冷杀菌技术是食品工业中新型杀菌技术之一,由于其高效,安全且能保持食品品质及感官特性,因此在未来食品杀菌领域具有广阔的应用前景。该文介绍了姜黄素介导光动力冷杀菌技术的杀菌机理和影响食品杀菌效果的因素,并与其他冷杀菌技术进行比较。在此基础上,总结了姜黄素介导的光动力冷杀菌技术在食品杀菌中的研究进展,并对其未来应用前景进行了展望。     

光动力杀菌机制及在食品应用中的优势与不足

有害微生物是引起食品安全问题的重要原因之一。广谱抗生素的使用虽然有效地抑制了有害微生物,但耐药性导致其无法得到有效控制,这加重了食品安全隐患,同时造成更严重的经济损失。因此,迫切需要开发其它替代杀菌技术,这也是保护食品安全的重要挑战。光动力杀菌技术是通过光激发光敏剂后,产生的活性氧物质破坏致病菌的形态结构、细胞膜、核酸和蛋白质等,同时触发多种细菌难以抵消的死亡机制,此机制不易造成细菌耐受性。光动力杀菌技术杀菌效果佳,但此杀菌技术对食品营养成分及品质的影响关注较少,限制了其在食品领域中的推广和应用。本文系统综述了光动力杀菌技术的杀菌机制及影响因素,并且介绍了光动力杀菌在食品中的研究应用,就杀菌技术在食品应用中的优势和不足提出新见解,以期为我国光动力杀菌技术的工业化应用提供参考。     

加压CO_2在生理盐水中的杀菌效果研究

<正>CO2是一种天然、安全的杀菌剂,它的临界温度和临界压力分别为31.1℃、7.13MPa,加压CO2杀菌技术是利用高于或接近于临界温度和临界压力的CO2对食品进行杀菌。使用这项技术处理生理盐水中的大肠杆菌、枯草芽孢杆菌和金黄色葡萄球菌。选择不同的压力(1MPa、3MPa、5MPa和7.5MPa)、时间(15min、30min、45min和60min)、温度(25℃、35℃、45℃和55℃),研究影响杀菌效果的因素。结果表明随着压力、时间和温度提高,加压CO2的杀菌效果逐渐提高;加压CO2对3种菌的杀菌效果     

芦荟提取液抑菌效果的研究

对芦荟提取液的抑菌作用进行初步研究,结果表明:芦荟提取液对供试的几种主要危害食品卫生、安全和对临床医学等具有重要影响的大肠杆菌、金黄色葡萄球菌、枯草芽孢杆菌的生长均有一定抑制作用,但在杀菌实验中,芦荟的提取液对上述几种菌均无明显的杀菌效果。在不同浓度的抑菌效果中,30%的芦荟提取液对供试菌种的抑制效果最强,对供试菌种的最低抑菌浓度金黄色葡萄球菌为10%;大肠杆菌为9%;枯草芽孢杆菌为11%。芦荟提取液能耐受高温短时的热处理。     

光动力技术及其在生鲜食品保鲜中的应用研究进展

生鲜食品产量很大,其在贮运过程中极易受到微生物的污染而产生腐败变质,引发食用安全风险并造成经济损失。热杀菌是目前常用的一种杀菌方法,但会影响生鲜食品的风味、色泽和营养,且不适用于热敏感性的食品物料。非热杀菌方法可以在一定程度上弥补这个不足,光动力技术就是其中之一。目前针对光动力技术在生鲜食品中的应用已经开展了一定的研究,基于此,作者概述了光动力技术的定义和杀菌原理,总结了其对不同微生物的杀灭效果和作用机制,并介绍了该技术在水产品、果蔬、乳品和肉制品中的应用及其对这些食品品质的影响,为光动力技术在水产品、果蔬、乳制品、肉制品等生鲜食品保鲜和安全控制中的应用提供一定的借鉴和参考。     

气体二氧化氯对苹果表面细菌杀菌规律研究

本实验研究了气体二氧化氯杀灭金黄色葡萄球菌、大肠杆菌、单核细胞增生李斯特氏菌以及腐生酵母菌四种苹果表面的危险致病菌的杀菌规律.在杀菌时间5min、杀菌温度25℃条件下,金黄色葡萄球菌、大肠杆菌、单核细胞增生李斯特氏菌和腐生酵母菌杀菌达到99.99%的杀菌率,所需的气体二氧化氯的浓度分别为23、21、6和11mg/L.在杀菌气体二氧化氯浓度10mg/L、杀菌温度25℃时,四种菌杀菌时间分别达到7、8、2和6.5min时,杀菌率均超过99.99%.在实验范围内,作用温度对杀菌效果影响不大.     

罗勒叶叶绿素锌钠盐的制备及其稳定性研究

通过正交试验研究罗勒叶中叶绿素浸提的最佳工艺条件,经过皂化、酸化、锌代及其成盐反应制备叶绿素锌钠盐,并对其稳定性进行研究.结果表明,罗勒叶叶绿素的最佳浸提工艺条件为:乙醇浓度100％,浸提时间50 min,料液比为1:10,温度控制在70℃.而其制备的叶绿素锌钠盐水溶性、耐热性、耐氧化还原性、在弱酸、中性及碱性条件下较稳定,但在光照条件下,稳定性差.常用的食品添加剂和一些金属离子对叶绿素锌钠盐的稳定性无影响,Cu2+、Fe3+对叶绿素锌钠盐的稳定性有较大的影响.     

光动力对金黄色葡萄球菌的杀伤作用及其AFM观察

通过细菌菌落计数以及原子力显微镜图像研究了血啉甲醚对金黄色葡萄球菌的光动力杀伤作用。结果表明:HMME在金黄色葡萄球菌菌液中的最强吸收峰为392nm,溴钨灯光源波长范围350～2500nm,能满足HMME所需的波长;HMME浓度为5μg/mL接受溴钨灯光源光照30min能杀死82.2%的金黄色葡萄球菌;原子力显微镜图像显示其灭菌机制是HMME在光照条件下导致菌体破裂,细胞内容物大量外泄;无光照条件下,HMME对金黄色葡萄球菌杀伤效果不显著。     

2015年南宁市动物源性食品中金黄色葡萄球菌污染状况及耐药调查

目的调查2015年南宁市市售的动物源性食品中金黄色葡萄球菌的污染情况以及流行菌株的耐药情况,为食源性疾病监控提供数据支撑。方法随机采集市售的不同种类的动物源性食品383份,按照国标法进行金黄色葡萄球菌分离鉴定,并对分离到的28株金黄色葡萄球菌进行K-B纸片法耐药试验和PCR方法检测耐药基因。结果从383份动物源性食品中分离到28株金黄色葡萄球菌,耐药试验结果发现,其中10株为耐甲氧西林金黄色葡萄球菌,28株分离株对不同的抗菌药物有不同程度的耐药,并检测到了4类耐药基因。结论市售动物源性食品中有金黄色葡萄球菌污染,存在引发食物中毒的风险;分离株的耐药试验结果可以为南宁市金黄色葡萄球菌引起的食物中毒提供用药参考。     

Effects of pulsed electric fields on pathogenic microorganisms of major concern in fluid foods: a review

Pathogenic microorganisms such as Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes, Bacillus cereus, Staphylococcus aureus, Yersinia enterocolitica, and Campylobacter jejuni have been implicated in foodborne diseases and outbreaks worldwide. These bacteria have been associated with the consumption of fresh fruit juices, milk, and dairy products, which are foodstuff, highly demanded by consumers in retails and supermarkets. Nowadays, consumers require high quality, fresh-like, and safe foods. Pulsed electric field (PEF) is a non-thermal preservation method, able to inactivate pathogenic microorganisms without significant loss of the organoleptic and nutritional properties of food. The PEF treatment effectiveness to destroy bacteria such as Listeria innocua, E. coli, Salmonella Typhimurium, E. coli O157:H7 and E. coli 8739 at pasteurization levels (> or = 5.0 log(10) cycles) in some fluid foods was reported. However, data on the inactivation of some microorganisms such as Bacillus cereus, Staphylococcus aureus, Yersinia enterocolitica, and Campylobacter jejuni in fluid foods by PEF processing is very limited. Therefore, future works should be focused toward the inactivation of these pathogenic bacteria in real foods.     

食品中金黄色葡萄球菌平板计数不确定度评定

为更好地评估食品中金黄色葡萄球菌指标。方法 按GB 4789.10—2010方法检验食品中金黄色葡萄球菌,按JJG 196—2006对菌落平板计数结果进行不确定度评定。结果 测量结果的扩展不确定度为U=0.072×lgT(T-食品中金黄色葡萄球菌菌落数),k=2。结论 测量不确定度评定可更为准确地评价食品质量,确保出厂食品的安全。     

2013年云南省市售特色食品中细菌性污染情况调查

调查云南省市售特色食品中细菌污染状况。 方法 采用国家标准规定的检测方法,对2013年云南省4个有代表性的州市市售特色食品进行卫生指标菌和常见食源性致病菌检测,并用SPSS 19.0软件对测定结果进行分析。 结果 在10类食品的288份样品中卫生指标菌不合格率为56.50%,食源性致病菌总检出率为12.15%,均为散装产品;沙门菌主要来自凉拌生猪皮和凉拌食品,检出率分别为8.33%和3.13%;金黄色葡萄球菌检出最高的为凉拌生猪皮,为31.25%,其次为乳扇25.00%;蜡样芽胞杆菌在凉拌食品中检出率低(7.81%);志贺菌和致泻大肠埃希菌在散装食品中未检出。全年4个季度沙门菌和金黄色葡萄球菌的检出率差异无统计学意义(P＞0.05)。 结论 云南省市售特色食品,特别是散装样品,细菌性污染严重。考虑到食品的即食性,原料来源不可控,无熟制过程,存在较大食品安全隐患,应进一步加强相关食品的卫生监管。     

Contribution of wine components to inactivation of food-borne pathogens

ABSTRACT:  Wine is a complex solution containing several components with several likely antimicrobial properties. Low pH (3.0 to 4.0), high organic acid content (titratable acidity ≥6.0 g/L tartaric acid), relatively high ethanol (10% to 15%), and potentially high total sulfur dioxide (0 to 300 ppm) may contribute to inactivation of food-borne pathogens when exposed to wine. The objective was to determine the effect of these 4 parameters on reducing populations of Escherichia coli ( E. coli ) O157:H7 and Staphylococcus aureus . A factorial design was used to test variables (pH, titratable acidity, sulfur dioxide, ethanol) in combinations of low, medium, and high levels. Suspension tests were performed to compare the efficacy of 81 treatments with controlled exposure time of 20 min. Staphylococcus aureus was significantly more resistant to wine treatment than E. coli O157:H7. Stepwise regression analysis of S. aureus inactivation revealed the ordered impact of pH, molecular sulfur dioxide, titratable acidity, and ethanol concentration. Selected analysis of E. coli inactivation revealed the importance of pH and ethanol in predicting inactivation. Total and free sulfur dioxide were not predictive of inactivation of either pathogen. Wine-based solutions may have application as surface disinfectants for food surfaces and food contact equipment. Wine destined to be used as a disinfectant could be enhanced by increasing any of the parameters tested in this study; however, lowering the pH would be the most effective and would likely enhance the efficacy of the other parameters. Additional wine components such as volatile acidity and phenolics were not evaluated but may also contribute to the antimicrobial properties of wine.     

INACTIVATION OF STAPHYLOCOCCUS AUREUS EXPOSED TO DENSE-PHASE CARBON DIOXIDE IN A BATCH SYSTEM

ABSTRACT

The inactivation of Staphylococcus aureus exposed to dense‐phase carbon dioxide (DPCD) was investigated, and the kinetics of come‐up time (CUT) in pressurization was monitored with come‐down time (CDT) and temperature fluctuation in depressurization. CUT was about 2.5, 3.5, 4.0 and 4.0 min; CDT was 3.4, 3.7, 4.5 and 4.5 min; lowest temperature of samples in depressurization was 4, ?1, ?15 and ?22C, corresponding to 10, 20, 30 and 40 MPa at 37C. The inactivation behavior of S. aureus was closely related to the variables of process pressure, holding‐pressure time (HPT), process temperature and process cycling. The log reduction of S. aureus at 40 MPa for 30‐min HPT was significantly greater (P < 0.05), but the inactivation effect at 10, 20 and 30 MPa was similar. The log reduction of S. aureus at 30 and 40 MPa for 60‐min HPT was similar and significantly greater (P < 0.05), while the inactivation effect at 10 and 20 MPa was similar. The inactivation of S. aureus against HPT conformed to a fast–slow biphase kinetics; the two stages were well fitted to a first‐order model with higher regression coefficients R² = 1.000 and 0.9238; their respective D values (decimal reduction time) were 16.52 and 70.42 min. As the process temperature increased, the log reduction of S. aureus increased significantly (P < 0.05); the inactivation kinetics of S. aureus versus process temperature was characterized with a fast inactivation rate from 32 to 45C and a slow inactivation rate from 45 to 55C. As compared to one‐process cycling for a total of 60‐min HPT, four‐process cycling resulted in a significant reduction of S. aureus, and its maximal reduction was near to 5 log cycles, indicating that more process cycling caused more inactivation of S. aureus under identical pressure and temperature with equal HPT. However, the maximal reduction was 0.09 and 0.12 log cycles for two‐ and four‐process cyclings with 0‐min HPT, indicating that pressurization and depressurization had a lesser effect on the inactivation of S. aureus, while HPT was significant in DPCD to inactivate S. aureus.

PRACTICAL APPLICATIONS

Dense‐phase carbon dioxide (DPCD) is a novel technology to achieve cold pasteurization and/or sterilization of liquid and solid materials, and is likely to replace or partially substitute currently and widely applied thermal processes. This study showed that DPCD effectively inactivated Staphylococcus aureus inoculated in 7.5% sodium chloride broth, and the inactivation behavior of S. aureus was closely related to the pressure, holding‐pressure time, temperature and process cycling. Based on this observation, the technology of DPCD can be applied in the pasteurization of foods such as milk and various fruit juices, especially thermal‐sensitive materials.

     

四川省动物性食品中金黄色葡萄球菌的分离鉴定及污染分析

目的：为分析四川省动物性食品源金黄色葡萄球菌(Staphylococcus aureus,简称SA)的耐药性,收集菌株,同时分析动物性食品中SA的污染情况。方法：本实验自2006年12月至2007年9月从四川省各地采集猪源、牛源、鸡源动物性食品样品共2560份,利用选择性培养基和生化实验等常规方法分离鉴定SA。结果：用Baird-Parker平板初步筛出疑似SA 118株,结合国标中规定的涂片染色镜检,溶血现象和血浆凝固酶实验结果,判定SA 有108株,而科玛嘉金黄色葡萄球菌显色平板和TH-16S中的双歧索引鉴定结果均判定SA有 113株;依据TH-16S中的16项生化实验结果,118株疑似SA仅有64%(76株)的菌株鉴定为SA。依据国标判定结果,2560份样品中SA的分离率为4.21%,其中生牛奶中SA的分离率最高(10.54%),其次是猪肉(7.11%),鲜鸡蛋中SA的分离率为零。结论：四川地区动物性食品源SA的生化表型复杂且存在一定差异,常规的表型分析具有一定缺陷。各个地方各类样品中SA污染情况有一定差异,与其他报道相比,四川省生肉、生奶和鲜蛋中SA的分离率较低。     

Predicting heat inactivation of Staphylococcus aureus under nonisothermal treatments at different pH

The aim was to assess whether heat resistance data obtained from isothermal treatments allow the estimation of survivors of Staphylococcus aureus under nonisothermal conditions and to find a model that accurately predicts its heat inactivation at constantly rising heating rates (0.5-9 degrees C/min) in media of different pH (4.0-7.4). S. aureus showed a higher heat resistance under isothermal treatments at pH 4.0 than at pH 5.5-7.4. However, under nonisothermal treatments S. aureus increased its heat resistance at pH 5.5-7.4 and became more thermotolerant than at pH 4.0. Estimations of survival curves under nonisothermal treatments obtained from heat resistance parameters of isothermal treatments did not adequately fit experimental values. Whereas the number of survivors was much higher than estimated at pH 5.5-7.4, that obtained at the slower heating rates at pH 4.0 was lower. An equation based on the Weibullian-like distribution (log10 S(t) = (t/delta)p) accurately described survival curves obtained under nonisothermal conditions. A nonlinear relationship was observed among the scale parameter (delta) and the heating rate which allowed the development of two equations capable of predicting the inactivation rate of S. aureus under nonisothermal treatments. This study might contribute to prevent public health risks in foods requiring long heating lag phases during their processing.     

2018年北京市通州区居民冰箱使用习惯及卫生状况调查

目的 了解北京市通州区居民冰箱储存食物、清洗频率等使用习惯及卫生状况。方法 选取北京市通州区3个社区60户居民, 调查冰箱使用年限、冰箱内部是否定期清洗、水果、鸡蛋和熟食的储存习惯等。对冰箱冷藏室隔板和底部进行涂抹采样, 检测项目为大肠菌群、单核细胞增生李斯特菌、小肠结肠炎耶尔森菌和金黄色葡萄球菌。结果 调查居民60台冰箱, 使用年限<10年的占76.7%, 定期清洗冰箱的占80.0%。有41.6%的居民在冰箱冷藏室存放熟食与其他食物混放, 20.0%的居民将水果不包装放入冰箱, 13.3%的居民将鸡蛋与其他食物混放。采集冰箱内部涂抹样品120件, 大肠菌群检出率为31.7%(38/120), 冷藏室底部大肠菌群检出率高于冷藏室隔板(2=5.546, P=0.019)。未检出单核细胞增生李斯特菌、小肠结肠炎耶尔森菌、金黄色葡萄球菌。结论 居民冰箱储存食物方式及冷藏室卫生状况存在食品安全隐患, 因此应加强宣教和指导, 预防和减少食源性疾病发生。