鲅鱼贮藏过程中的品质变化和货架期预测

将感官、微生物和化学变化作为检测指标,对鲅鱼(Scomberomorus niphonius)在0℃、4℃、15℃、22℃和25℃贮藏过程中的品质变化和货架期进行研究。通过化学分析研究,对菌落总数(TVC)、挥发性盐基氮(TVB-N)、三甲胺(TMA)与感官评价的一致性进行探讨。结果表明,在0℃、4℃、15℃、22℃和25℃贮藏过程中鲅鱼较好品质的时期分别为192h、144h、24h、18h和12h,货架期终点分别为240h、192h、48h、24h和20h。各个温度条件下,鲅鱼贮藏过程中较好品质期和货架期终点的TVB-N平均值分别为(22.88±1.98)mg/100g、(49.40±2.40)mg/100g;TMA均值为(11.67±1.88)mg/100g、(18.88±2.75)mg/100g;菌落总数分别为(4.01±0.49)lg(CFU/g)、(6.17±0.49)lg(CFU/g);产H2S菌数分别为(3.28±0.63)lg(CFU/g)、(5.78±0.65)lg(CFU/g),、假单胞菌数分别为(3.60±0.39)lg(CFU/g)、(6.12±0.50)lg(CFU/g)。可知TVB-N、TMA、菌落总数、产H2S菌、假单胞菌作为鲅鱼贮藏过程中的鲜度指标与感官评价具有一致性。     

臭氧结合超声协同低浓度次氯酸钠复合处理对冰鲜鸡腿的保鲜效果

为降低肉鸡宰后鸡体表面初始菌数,延长冰鲜鸡货架期,探究臭氧水处理（ozone,OZ）、超声协同次氯酸钠处理（ultrasound assisted sodium hypochlorite,SH-US）、臭氧结合超声协同低浓度次氯酸钠复合处理（ultrasound assisted sodium hypochlorite and ozone,SH-US-OZ）3种减菌方式对鸡腿表面减菌效果和对其托盘包装贮藏期间保鲜效果的影响。结果表明,3种减菌处理均可以显著降低冰鲜鸡腿表面初始微生物数量（P<0.05）,其中,SH-US-OZ复合处理减菌效果最好。该处理将初始菌落总数从5.72(lg(CFU/g))降低到4.25(lg(CFU/g)),减菌率为96.6%,有效延缓了微生物在贮藏期间的生长速率、提升了鸡腿贮藏期间的表面亮度值和感官品质、减少了贮藏损失和挥发性盐基氮含量。虽然该复合处理组增加了脂质氧化程度、降低了表面红度值,但未引起感官劣变。因此,SH-US-OZ复合处理在减少次氯酸钠使用的基础上具有显著的减菌和保鲜效果,有效保持鸡腿贮藏期间的品质,将货架期延长至5 d以上。     

养殖尼罗罗非鱼鲜度特征及动力学模型构建

通过感官、化学、微生物学方法对低温(0～10℃)和室温(25℃)贮藏尼罗罗非鱼鲜度特征进行评价,确定产品货架期及货架期终点细菌种群,运用平方根相对腐败速率方程构建货架期预测模型。结果表明:鲜鱼感官品质良好,菌落总数、假单胞菌数、产H2S细菌数和挥发性盐基氮(TVBN)分别为(4.41±1.13)、(3.39±1.09)、(2.01±0.88)(lg(CFU/g))和(8.53±0.73)mg/100g。低温贮藏罗非鱼货架期终点时,菌落总数、假单胞菌、产H2S细菌数和TVBN分别为(7.79±0.35)、(7.24±0.45)、(6.35±0.23)(lg(CFU/g))和(19.90±2.10)mg/100g,确定货架期为5.5～20.1d,优势菌是假单胞菌属,而室温贮藏的罗非鱼货架期为1.3d,优势菌为气单胞菌。0～25℃范围贮藏的罗非鱼品质动力学模型参数Tmin为-8.9℃,并用3、8℃恒温和变温等实际流通条件对货架期预测模型进行了验证,显示货架期预测模型能有效评价0～25℃范围内的罗非鱼品质。     

PCR-DGGE结合生理生化鉴定分析冷藏金枪鱼细菌菌相变化

以感官、色差、质构、挥发性盐基氮(TVB-N)、K值以及菌落总数、嗜冷菌总数为鲜度指标,研究4℃冷藏金枪鱼贮藏期间品质变化;并结合生理生化鉴定和16S rDNA,应用变性梯度凝胶电泳(DGGE)指纹图谱技术,分析冷藏金枪鱼主要微生物的菌相演替变化规律。结果表明:冷藏期间,金枪鱼感官品质劣变明显,亮度值L*、红度值a*和咀嚼性、硬度均呈下降趋势;贮藏第4天,菌落总数自3.60 lg (CFU/g)升至4.66 lg (CFU/g),而嗜冷菌数与菌落总数之间的差异减小;贮藏第6天,TVB-N值与K值分别由初始值9.62 mg/100 g和3.22%上升至25.00 mg/100 g和23.00%;不同冷藏时期的金枪鱼中微生物群落结构具有相似性,样品初始菌相中主要优势菌为噬氢菌、不动杆菌、假单胞菌、解糖假苍白杆菌、Boseaeneae、鞘氨醇单胞菌和油短波单胞菌。随着贮藏时间的延长,微生物多样性降低,至货架期终点第6天,红游动菌、约氏不动杆菌、假单胞菌、解糖假苍白杆菌成为主要优势腐败菌。     

PCR-DGGE研究热鲜肉贮藏过程中的菌相变化

应用传统微生物培养和聚合酶链式反应-变性梯度凝胶电泳(PCR-DGGE)方法研究热鲜肉分别在5、15、25、30℃贮藏过程中的菌相变化。将热鲜肉贮藏于一定温度,每隔适当时间取出,测定菌落总数,并提取细菌DNA,进行PCR-DGGE分析。细菌计数结果表明,热鲜肉贮藏于5、15、25、30℃时,菌落总数分别在约14d、75h、19h和16h达到最小腐败量7.2(lg(CFU/g))。PCR-DGGE结果表明,热鲜肉在不同温度下贮藏时,贮藏末期优势腐败菌并不一致。在贮藏过程中主要优势腐败菌有巨大球菌属、克雷伯氏菌属、假单胞菌属、柠檬酸细菌属、不动杆菌属和埃希氏菌属。     

壳聚糖-普鲁兰多糖复合抗菌保鲜膜对冷鲜牛肉的保鲜效果

开发了一种适用于冷鲜牛肉保鲜的具有抗菌功能的可食性抗菌保鲜膜。将4 mg/mL的ε-聚赖氨酸(ε-PL)添加到壳聚糖-普鲁兰多糖溶液中,制备具抗菌功能的可食性复合抗菌保鲜膜,并验证该保鲜膜具有良好的理化特性和抗菌效果。冷鲜牛肉贮藏过程中优势致病菌(大肠O157:H7,单增李斯特菌和沙门氏菌)和菌落总数等指标检测结果表明,贮藏9天,对照组菌落总数就达到8.09 lg(CFU/g),而处理组增长较缓慢,第13天为5.94lg (CFU/g)。贮藏末期,处理组大肠O157:H7、单增李斯特菌和沙门氏菌较对照组分别减少了5.12,4.47 lg(CFU/cm2)和5.54 lg(CFU/cm2)。通过比较分析冷鲜牛肉贮藏过程中感官、质地、挥发性盐基氮(TVBN)、pH值、色度指标(a*/b*)等指标,表明该膜对于减缓冷鲜牛肉品质劣变具有显著效果。该保鲜膜对于控制牛肉品质劣变、延长货架期具有良好效果。     

超声波协同微酸性电解水对小龙虾净化及品质的影响

为了探究小龙虾（Procambarus clarkii）的净化工艺,采用超声波清洗协同微酸性电解水减菌技术对小龙虾进行活体净化处理。本文以小龙虾的菌落总数、芽孢总数及清洗液浊度为评价指标,以微酸性电解水的有效氯浓度、浸泡时间以及超声波功率为单因素水平,研究了微酸性电解水对小龙虾的减菌效果和超声波对小龙虾的清洗效果。结果表明:微酸性电解水的有效氯质量浓度越高,处理时间越长减菌效果越好。当微酸性电解水有效氯质量浓度60 mg/L,处理小龙虾50 min后菌落总数和芽孢总数分别下降了4.26 lg CFU/g、500 CFU/g,减菌率分别达到了99.99%、92.61%;使用超声波技术对小龙虾进行清洗处理,超声功率50 W处理50 min后小龙虾存活率为100%,清洗液浊度为181 NTU,显著优于对照组（P<0.05）。超声波技术协同微酸性电解水对小龙虾活体净化处理后,小龙虾初始菌由7.17 lg CFU/g降到3.52 lg CFU/g,净化效果显著优于车间气泡清洗工艺（P<0.05）。小龙虾净化前后的营养价值和品质无显著性差异（P>0.05）,该工艺合理有效。     

响应曲面法优化草鱼肉冷杀菌工艺

以微生物菌落总数和减菌率为评价指标,采用单因素试验结合Box-Behnken法,研究ClO2质量浓度、H2O2质量浓度及浸泡处理时间对草鱼肉冷杀菌效果的影响。通过响应曲面分析,草鱼肉减菌预处理工艺最优条件为ClO2质量浓度157mg/L、H2O2质量浓度1.1g/L、浸泡处理时间6.4min,在此条件下草鱼肉经处理后细菌总数由1.36×105CFU/g降为1.50×104CFU/g,减菌率高达89.01%。     

介质阻挡放电低温等离子体在鲐鱼杀菌及组胺含量控制中的作用

为探究介质阻挡放电低温等离子体(atmospheric cold plasma,ACP)处理鲐鱼的杀菌效果以及在控制组胺含量中的作用,分别采用ACP直接处理和间接处理两种方式,分析鲐鱼菌落总数的变化,并通过响应面法中心组合设计优化了ACP杀菌的最佳处理电压和时间;在此基础上,探索ACP对鲐鱼贮藏过程中组胺含量以及与组胺产生有关的假单胞菌、肠杆菌、弧菌的影响。结果表明:直接处理对鲐鱼的杀菌效果更优,菌落总数降低率比间接处理高35.88%;最佳处理条件为处理电压59.9 k V、处理时间71.5 s;在优化条件下,鲐鱼菌落总数为1.83(lg(CFU/g)),与预测值1.86(lg(CFU/g))相差不大,所建模型与实际拟合较好;经ACP处理后的鲐鱼在贮藏期(14 d)内,假单胞菌、肠杆菌、弧菌的生长速率明显低于对照组;贮藏第8天时,假单胞菌、肠杆菌、弧菌的菌落数比对照组分别降低25.89%、46.23%和45.23%;组胺含量在贮藏期内增长较慢,第14天时含量为72.34 mg/100 g,低于国标限量。     

壳寡糖对冷鲜牛肉保鲜效果的影响

以冷鲜牛肉为研究对象,采用不同质量浓度的壳寡糖(0、0.04、0.06、0.08 g/100 m L)对冷鲜牛肉处理后真空包装,在(0~4)℃的条件下贮藏30 d,每隔5 d取样测定牛肉的挥发性盐基氮(TVB-N)值、肉糜脂肪氧化程度(TBARS)值、高铁肌红蛋白值(met Mb%)、色差(L*、a*和b*)、质构(硬度、弹性、黏性)的理化指标以及菌落总数、大肠杆菌的微生物指标。结果表明:冷鲜牛肉的TVB-N值、TBARS值、met Mb%、硬度以及菌落总数和大肠杆菌数都随贮藏时间延长而呈现增加的趋势,L*、a*和b*值、弹性和黏度值一直降低。经壳寡糖处理过的实验组各项指标相对空白对照组变化较为缓慢,且当壳寡糖质量浓度为0.06 g/100 m L时,保鲜效果最佳。在第20天时,0.06 g/100 m L壳寡糖处理的冷鲜牛肉的挥发性盐基氮(TVB-N)值为17.47 mg/100 g、菌落总数的值为5.18 lg(CFU/g)、大肠杆菌的值为5.35 lg(CFU/g),均未超出国家标准,货架期由原来的10 d延长至20 d,而且使牛肉的色泽与营养在更长的保存时间内保持不变。     

Inactivation kinetics of inoculated Escherichia coli O157:H7, Listeria monocytogenes and Salmonella Poona on whole cantaloupe by chlorine dioxide gas

The objectives of this study were to examine inactivation kinetics of inoculated Escherichia coli O157:H7, Listeria monocytogenes and Salmonella Poona inoculated onto whole cantaloupe and treated with ClO(2) gas at different concentrations (0.5, 1.0, 1.5, 3.0 and 5.0 mg l(-1)) for different times (0, 2.0, 4.0, 6.0, 8.0 and 10.0 min). The effect of ClO(2) gas on the quality and shelf life of whole cantaloupe was also evaluated during storage at 22 degrees C for 12 days. A 100 microl inoculation of each targeted organism was spotted onto the surface (5 cm(2)) of cantaloupe rind (approximately 8-9 log CFU 5 cm(-2)) separately, air dried (60 min), and then treated with ClO(2) gas at 22 degrees C and 90-95% relative humidity for 10 min. Surviving bacterial populations on cantaloupe surfaces were determined using a membrane transferring method with a non-selective medium followed by a selective medium. The inactivation kinetics of E. coli O157:H7, L. monocytogenes and S. Poona were determined using nonlinear kinetics (Weibull model). A 3 log CFU reduction of E. coli O157:H7, L. monocytogenes and S. Poona were achieved with 5.0 mg l(-1) ClO(2) gas for 5.5, 4.2 and 1.5 min, respectively. A 5l og CFU reduction of S. Poona was achieved with 5.0 and 3.0 mg l(-1) ClO(2) gas for 6 and 8 min, respectively. A 4.6 and 4.3 log reduction was achieved after treatment with 5.0 mg l(-1) ClO(2) gas at 10 min for E. coli O157:H7 and L. monocytogenes, respectively. Treatment with 5.0 mg l(-1) ClO(2) gas significantly (p<0.05) reduced the initial microflora (mesophilic bacteria, psychrotrophic bacteria, and yeasts and molds) on cantaloupe by more than 2 log CFU cm(-2) and kept them significantly (p<0.05) lower than the untreated control during storage at 22 degrees C for 12 days. Treatment with ClO(2) gas did not significantly (p>0.05) affect the color of whole cantaloupe and extended the shelf life to 9 days compared to 3 days for the untreated control, when stored at ambient temperature (22 degrees C).     

二氧化氯对鲳鱼微冻贮藏品质的影响

用二氧化氯（ClO2）处理鲳鱼块后进行微冻（－3 ℃）贮藏,测定贮藏期间鱼肉的菌落总数、菌相、总挥 发性盐基氮（total volatile basis nitrogen,TVB-N）含量、K值、pH值及肌原纤维储能模量（G’）的变化,考察ClO2 处理对鲳鱼块微冻贮藏品质的影响。结果表明：30 μg/mL ClO2处理（料液比1∶20（m/V）,浸泡10 min）可以使鱼 块的初始菌落总数降低约2 （lg（CFU/g））。贮藏过程中,处理组鱼块的菌落总数始终低于对照组,但贮藏初期 处理组鱼块的细菌生长速率明显高于对照组;2 组鱼块的优势腐败菌均由初期的希瓦氏菌属过渡到末期的假单胞菌 属;根据鱼肉的TVB-N含量,对照组于贮藏第20天变为二级鲜度,而处理组在贮藏的32 d内一直处于一级鲜度; ClO2处理使鱼肉初始pH值下降0.52,贮藏期间处理组鱼肉的pH值始终低于对照组约0.2～0.4;贮藏期间2 组鱼肉 的K值差别不大,对照组和处理组分别于贮藏12、16 d达到40%;处理组鱼肉的肌原纤维蛋白G’峰值始终高于对照 组。上述结果表明,ClO2处理结合微冻贮藏能够有效提升鲳鱼块鲜度、延长其货架期。     

Decontamination of strawberries using batch and continuous chlorine dioxide gas treatments

Efficacy of chlorine dioxide (ClO2) gas in reducing Escherichia coli O157:H7 and Listeria monocytogenes on strawberries was determined using batch and continuous flow ClO2 gas treatment systems. Effects of continuous ClO2 gas treatment on total aerobic plate count, color, and residual ClO2 and chlorite on strawberries were also evaluated. Strawberries were spot inoculated with 7 to 8 log CFU per strawberry of each pathogen (E. coli O157:H7 and L. monocytogenes), stored for 1 day at 4 degrees C, and treated at 22 degrees C and 90 to 95% relative humidity with 0.2 to 4.0 mg/liter ClO2 gas for 15 or 30 min using a batch treatment system or with 0.6, 1.8, and 3.0 mg/liter for 10 min using a continuous treatment system. Surviving microbial populations were determined using a membrane-transfer plating recovery method. Increased ClO2 gas concentrations resulted in increased log reductions of each pathogen for both the batch and continuous systems. A batch treatment of strawberries with 4 mg/liter ClO2 for 30 min and continuous treatment with 3 mg/liter ClO2 for 10 min achieved greater than a 5-log reduction for both E. coli O157:H7 and L. monocytogenes. After continuous exposure to 3.0 mg/liter ClO2 gas for 10 min followed by 1 week of storage at 4 degrees C, no aerobic microorganisms were detected and the color of the strawberry surface did not change significantly (P > 0.05). Residues of ClO2 and chlorite on strawberries after the treatment were 0.19 +/- 0.33 mg ClO2 per kg and 1.17 +/- 2.02 mg Cl2 per kg, respectively, whereas after 1 week of storage no ClO2 residues were detected and residual chlorite levels were down to 0.07 +/- 0.12 mg Cl2 per kg. These results suggest that ClO2 gas treatment is an effective decontamination technique for improving the safety of strawberries while extending shelf life.     

Inactivation kinetics of inoculated Escherichia coli O157:H7 and Salmonella enterica on lettuce by chlorine dioxide gas

The purpose of this investigation was to study inactivation kinetics of inoculated Escherichia coli O157:H7 and Salmonella enterica on lettuce leaves by ClO(2) gas at different concentrations (0.5, 1.0, 1.5, 3.0, and 5.0 mg l(-1)) for 10 min and to determine the effect of ClO(2) gas on the quality and shelf life of lettuce during storage at 4 degrees C for 7 days. One hundred microliters of each targeted organism was separately spot-inoculated onto the surface (5 cm(2)) of lettuce (approximately 8-9 log CFU ml(-1)), air-dried, and treated with ClO(2) gas at 22 degrees C and 90-95% relative humidity for 10 min. Surviving bacterial populations on lettuce were determined using a membrane transferring method, which included a non-selective medium followed by a selective medium. The inactivation kinetics of E. coli O157:H7 and S. enterica was determined using first-order kinetics to establish D-values and z-values. The D-values of E. coli and S. enterica were 2.9+/-0.1 and 3.8+/-0.5 min, respectively, at 5.0 mg l(-1) ClO(2) gas. The z-values of E. coli and S. enterica were 16.2+/-2.4 and 21.4+/-0.5 mg l(-1), respectively. A 5 log CFU reduction (recommended by the United States Food and Drug Administration) for E. coli and S. enterica could be achieved with 5.0 mg l(-1) ClO(2) gas for 14.5 and 19.0 min, respectively. Treatment with ClO(2) gas significantly reduced inherent microflora on lettuce and microbial counts remained significantly (p<0.05) lower than the uninoculated control during storage at 4 degrees C for 7 days. However, treatment with ClO(2) gas had a significantly (p<0.05) negative impact on visual leaf quality. These results showed that treatment with ClO(2) gas significantly reduced selected pathogens and inherent microorganisms on lettuce; however, the processing conditions would likely need to be altered for consumer acceptance.     

高压均质对芒果汁中大肠杆菌的杀菌动力学

为预测高压均质(high pressure homogenization,HPH)对芒果汁中大肠杆菌的杀菌作用,进行了压力40~190 MPa、进料温度20~60℃和均质次数1~5次的HPH实验,并运用Weibull模型对杀菌致死曲线进行动力学分析。研究表明:随压力、进料温度和均质次数的升高,HPH对芒果汁中大肠杆菌的杀菌效果增强。50℃HPH处理芒果汁,压力由40 MPa升高至190 MPa时,大肠杆菌降低量由0.46(lg(CFU/mL))增加至5.16(lg(CFU/mL)),达到美国食品药物管理局规定的非热加工杀菌卫生安全要求;70 MPa HPH处理芒果汁,进料温度由20℃升高至60℃时,大肠杆菌降低量由0.34(lg(CFU/mL))增加至5.02(lg(CFU/mL));20℃、190 MPa HPH处理芒果汁,均质次数由1增加至4时,大肠杆菌降低量由1.73(lg(CFU/mL))增加至5.15(lg(CFU/mL))。通过Weibull模型拟合杀菌致死曲线,并对模型进行简化,发现简化的Weib ull模型在20~50℃、40~190 MPa均质1次和20~40℃、190 MPa均质1~5次时拟合性较好(R~20.92)。简化的Weibull模型可用于预测进料温度-压力和进料温度-均质次数的杀菌效果,可为芒果汁的HPH生产过程中微生物安全性的控制提供理论依据。     

ClO2杀菌复合壳寡糖涂膜对鲜食糯玉米的保鲜效果

分别采用ClO2杀菌处理、壳寡糖（chitosan oligosaccharide,COS）涂膜处理以及ClO2杀菌复合COS涂膜（ClO2-COS）处理鲜食糯玉米,对比不同保鲜处理对鲜食糯玉米贮藏期间的抑菌情况、多酚含量、木质素含量、木质素积累速率、苯丙氨酸解氨酶活力、过氧化物酶活力的影响。结果发现：200 mg/L的ClO2杀菌复合15 mg/mL COS涂膜处理表现出良好的抑菌能力,贮藏35 d时霉菌和酵母菌总数为（2.30±0.12）（lg（CFU/g））,显著低于ClO2杀菌处理组（（3.78±0.16）（lg（CFU/g）））和COS涂膜处理组（（4.18±0.09）（lg（CFU/g）））（P＜0.05）;ClO2-COS处理能够降低木质素积累速率,降低多酚含量并使其基本保持较低水平;ClO2-COS处理可以抑制苯丙氨酸解氨酶活力过快上升,降低苯丙烷代谢水平,还能降低过氧化物酶活力,使其在贮藏期间一直保持较低水平,从而减少木质素积累。     

解冻猪肉中优势腐败菌致腐能力研究

将解冻猪肉中的优势腐败菌(假单胞菌属、热死环丝菌和肠杆菌科)接种到灭菌肉上研究其在不同温度贮藏过程中腐败的特点。在贮藏期间每天进行感官评价,测定各腐败菌的菌落数(CFU)、挥发性盐基氮(TVB-N)、脂肪氧化值,并以产生腐臭味时的TVB-N产量因子Y(TVB-N/CFU)作为各优势腐败菌腐败能力的定量指标。研究结果表明：至贮藏期第5天时解冻猪肉已产生强烈的腐臭味,热死环丝菌菌数在4、0℃和－5℃贮藏时分别达11.28lg(CFU/g)、9.63lg(CFU/g)和6.62lg(CFU/g),而相应的TVB-N值分别达14.92、14.50mg/100g和9.10mg/100g;与之类似,假单胞菌属菌数4、0℃和－5℃贮藏时分别达9.46lg(CFU/g)、8.87lg(CFU/g)和5.37lg(CFU/g),TVB-N值分别达21.59、14.49mg/100g和8.97mg/100g。研究表明热死环丝菌和假单胞菌属导致解冻猪肉腐败能力较强。     

Efficacy of chlorine dioxide gas as a sanitizer of lettuce leaves

Aqueous solutions of sodium hypochlorite or hypochlorous acid are typically used to sanitize fresh fruits and vegetables. However, pathogenic organisms occasionally survive aqueous sanitization in sufficient numbers to cause disease outbreaks. Chlorine dioxide (ClO2) gas generated by a dry chemical sachet was tested against foodborne pathogens on lettuce leaves. Lettuce leaves were inoculated with cocktail of three strains each of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium and treated with CLO2 gas for 30 min, 1 h, and 3 h in a model gas cabinet at room temperature (22 +/- 2 degrees C). After treatment, surviving cells, including injured cells, were enumerated on appropriate selective agar or using the overlay agar method, respectively. Total ClO2, generated by the gas packs was 4.3, 6.7, and 8.7 mg after 30 min, 1 h, and 3 h of treatment, respectively. Inoculated lettuce leaves exposed to ClO2 gas for 30 min experienced a 3.4-log reduction in E. coli, a 4.3-log reduction in Salmonella Typhimurium, and a 5.0-log reduction in L. monocytogenes when compared with the control. After 1 h. the three pathogens were reduced in number of CFU by 4.4. 5.3, and 5.2 log, respectively. After 3 h, the reductions were 6.9, 5.4, and 5.4 log, respectively. A similar pattern emerged when injured cells were enumerated. The ClO2, gas sachet was effective at killing pathogens on lettuce without deteriorating visual quality. Therefore, this product can be used during storage and transport of lettuce to improve its microbial safety.     

Comparison of chemical treatments to eliminate enterohemorrhagic Escherichia coli O157:H7 on alfalfa seeds.

The focus of this study was to determine the efficacy of various chemicals in eliminating 2.04 to 3.23 log10 CFU/g of Escherichia coli O157:H7 from alfalfa seeds and to determine the survivability of the pathogen on seeds stored for prolonged periods at three temperatures. Significant (P < or = 0.05) reductions in populations of E. coli O157:H7 on inoculated seeds were observed after treatments with 500 and 1,000 ppm of active chlorine (as Ca[OCl]2) for 3 but not 10 min and with > or =2,000 ppm of Ca(OCl)2 regardless of pretreatment with a surfactant. Treatment with 20,000 ppm of active chlorine failed to kill 2.68 log10 CFU/g of seeds. Acidified NaClO2 (500 ppm) was effective in reducing populations of the pathogen by >2 logs per g. Acidified ClO2 significantly reduced populations of E. coli O157:H7 on seeds at concentrations > or =100 ppm, and 500 ppm of ClO2 reduced the pathogen from 2.7 log10 CFU/g to <0.5 CFU/g. Chlorine (as NaOCl) was not effective at concentrations < or =1,000 ppm; significant reduction was achieved only after treatment with 2,000 ppm for 3 or 10 min. Notable reduction in populations was observed after treatment with 30 or 70% C2H3OH, but there was a dramatic decrease in germination percentage. Treatment with 0.2% H2O2 significantly reduced populations, and the organism was not detected by direct plating after treatment with > or =1% H2O2. Significant reduction in population of E. coli O157:H7 occurred after treatment with 1% trisodium phosphate, 40 ppm of Tsunami and Vortexx, and 1% Vegi-Clean. A significant decrease in the number of E. coli O157:H7 on dry seeds was observed within 1 week of storage at 25 and 37 degrees C, but not at 5 degrees C. Between 1 and 38 weeks, populations on seeds stored at 5 degrees C remained relatively constant. The pathogen was recovered from alfalfa seeds initially containing 3.04 log 10 CFU/g after storage at 25 or 37 degrees C for 38 weeks but not 54 weeks.     

固体二氧化氯保鲜剂对夏黑葡萄保鲜效果的影响

目的：探讨固体二氧化氯保鲜剂对夏黑葡萄采后保鲜效果。方法：以不同用量(2.5、5、10g/kg)的固体二氧化氯保鲜剂处理夏黑葡萄,将处理后的夏黑葡萄贮藏于(1±1)℃、相对湿度80%～85%冷库中,研究不同处理对其生理生化品质的影响。结果：3种二氧化氯保鲜剂用量处理均能降低贮藏中葡萄果实的腐烂,减缓好果率的下降,10g/kg保鲜剂处理组好果率保持最高;但5g/kg和2.5g/kg保鲜剂处理比10g/kg处理能较好抑制褐变度、丙二醛含量、呼吸强度的上升和花色苷、可溶性固形物、可滴定酸的下降。结论：5g/kg二氧化氯保鲜剂处理效果最好,能显著延缓葡萄的衰老氧化进程。