辐照对真空包装鲫鱼的保藏作用及对鲫鱼中沙门氏菌属和志贺氏菌属的杀灭作用

为研究辐照对真空包装鲫鱼的保藏作用进行本试验.发现30℃条件下不适于辐照鲫鱼的保藏.在4℃条件下,2.5 kGy的辐照可明显延长鲫鱼的保存期,随着辐照剂量的增加,保存期不断延长.对辐照后鲫鱼进行微生物分析发现,辐照可明显地降低鲫鱼试样中菌落总数和大肠菌群数,1.0 kGy的辐照剂量可使鲫鱼中大肠菌群的MPN值小于30/100 g.1.0 kGy的辐照剂量可有效地杀灭鲫鱼中人工污染的志贺氏菌,1.5 kGy的辐照剂量可有效地杀灭鲫鱼中人工污染的沙门氏菌.     

TaqMan探针双重荧光PCR技术检测食源性沙门氏菌和志贺氏菌

目的 建立TaqMan探针双重荧光聚合酶链式反应(polymerase chain reaction,PCR)技术检测食源性沙门氏菌和志贺氏菌的方法。方法 通过比对沙门氏菌和志贺氏菌的基因组序列,选择同源性高、保守性好的区域设计特异性引物和探针,经过引探筛选、浓度调试等一系列优化,建立了食源性沙门氏菌和志贺氏菌双重荧光PCR核酸检测方法,并对其特异性、质粒最低检出限、菌液敏感性、重复性、稳定性以及实际样品进行了验证。结果 该方法与大部分食源性致病菌无交叉反应,特异性强;沙门氏菌和志贺氏菌质粒的最低检出限可达5 copies/μL,沙门氏菌菌液敏感性为1.0×102 cfu/mL,志贺氏菌菌液敏感性10 cfu/mL;质粒和菌液核酸梯度的批内和批间变异系数均在0.177%~1.958%之间,小于5.0%,具有较强的稳定性;标准曲线相关系数(R2)均大于0.999。结论 本研究成功建立了一种TaqMan探针双重荧光PCR技术同时检测食源性沙门氏菌和志贺氏菌的方法,该方法扩增时间短,只需要30min即可,而且特异性强、稳定性好,可用于疑似沙门氏菌和志贺氏菌污染样品的检测,为食品安全的快速检测提供技术支撑。     

基于免疫磁分离-双重荧光定量PCR的鲜猪肉中沙门氏菌和志贺氏菌的检测

目的使用免疫磁分离-双重荧光定量PCR方法实现对鲜猪肉中金黄色葡萄球菌和志贺氏菌的同时、快速检测。方法在37℃的条件下,利用特异性免疫磁球从250 m L循环体系中快速、有效地捕获目标菌。再通过特异性的引物与探针,对沙门氏菌和志贺氏菌进行双重荧光定量PCR检测。结果本研究方法针对鲜猪肉中沙门氏菌和志贺氏菌的检测限分别达到3.4 cfu/g和9.4 cfu/g。方法总体灵敏度、特异性和准确度均达到100%。此外,通过对30组实际样品的检测,该方法与传统标准方法的结果保持一致。结论本研究建立的免疫磁分离-双重荧光定量PCR方法比国标方法更快速和高效,适用于鲜猪肉中沙门氏菌和志贺氏菌的快速检测。     

食品中志贺氏菌检测技术研究进展

志贺氏菌是主要的食源性致病菌之一,其低感染剂量和严重危害性受到人们广泛关注。因此,探究出快速、灵敏、高效的志贺氏菌的检测方法,对于保障食品质量安全是至关重要的。志贺氏菌的检测方法可分为三大类:传统培养方法、免疫学方法和分子生物学方法,许多研究为使其在样品检测中更加实用,进行了不同程度的改进。本文综述近年检测志贺氏菌的技术,包括改良的传统方法、免疫学方法和分子生物学方法以及新兴检测方法。重点阐述这些方法的应用范畴和应用进展,为志贺氏菌检测方法的选择提供参考。     

牛奶中志贺氏菌PCR检测方法的建立

根据Genbank志贺氏菌侵袭性质粒抗原H (ipaH)基因序列, 自行设计引物, 扩增特异的326 bp核酸片段, 经过优化PCR扩增条件, 建立了志贺氏菌特异、敏感、快速的PCR检测方法, 并对牛奶中的志贺氏菌进行了检测.特异性试验结果表明, 志贺氏菌参考菌株均能扩增出特异的核酸片段, 大肠杆菌、巴氏杆菌、金黄色葡萄球菌、沙门氏菌、蜡样芽孢杆菌、变形杆菌、绿脓杆菌的扩增结果均为阴性.敏感性试验结果表明, 采用试剂盒提取基因组, 该方法的敏感性可达到1.75×102 cfu/mL.人工污染牛奶的模拟检测结果表明, PCR方法的检测限为1.75×103 cfu/mL.     

志贺氏菌噬菌体空间杀菌效力的研究

将福氏志贺氏菌噬菌体SF-2A、痢疾志贺氏菌噬菌体SD-11及宋氏志贺氏菌噬菌体SS-92以等比例混合后进行气雾喷洒分析其在空间的杀菌效力,以期在食品生产和加工中控制食源性志贺氏菌的污染。首先在空间分析不同噬菌体气雾喷洒后的杀菌活性和最佳作用浓度,其次将福氏、痢疾及宋氏志贺氏菌以等量进行混合,以3×105cfu/mL的终浓度进行人工喷洒污染,并以3×108cfu/mL的噬菌体混合物进行气雾喷洒,分别在喷洒后1 h,2 h和3 h检测宿主菌的数量。结果显示,噬菌体SF-2A、SD-11及SS-92均能在空间有效灭活其相应宿主菌,其混合溶液作用3 h后已检测不到志贺氏菌。由此可见,混合噬菌体能够有效控制志贺氏菌的污染,这为食品生产及加工中环境中的病原菌的污染控制提供了新途径。     

肉制品中志贺氏菌DNA的快速提取方法

肉制品中致病菌DNA的提取对PCR检测具有重要意义。以污染志贺氏菌的猪肉为材料,比较了沸水浴法、裂解液煮沸法、CTAB/SDS法、改良的碱性异硫氰酸胍法4种提取方法对志贺氏菌DNA的提取效果,并以提取的DNA为模板进行PCR检测。结果表明:改良的碱性异硫氰酸胍法提取志贺氏菌DNA的效果较好,猪肉中志贺氏菌的PCR最低检出限为5×100CFU/g,整个检测时间<8h。经改良的碱性异硫氰酸胍法操作简便、经济省时,可用于肉类的PCR检测。     

抗志贺氏菌IgY的提纯及建立间接ELISA检测志贺氏菌

采用水稀释法提纯抗志贺氏菌IgY,检测10mg/mL纯化抗志贺氏菌IgY的效价为1∶320,并以此IgY为基础建立间接ELISA检测志贺氏菌,测定志贺氏菌纯培养液的检出限为105～106cfu/mL。对蜡样芽孢杆菌等10株不同菌株的检测结果表明,该方法对志贺氏菌有明显的检测特异性,对所测定的其它菌株无交叉反应。     

乳中志贺氏菌的荧光定量PCR检测方法的建立

为了快速、有效的检测乳中的志贺氏菌,建立一种特异性强、灵敏度高的荧光定量PCR方法。根据GenBank公布的志贺氏菌ipaH基因的保守序列设计特异性引物,对提取的志贺氏菌DNA模板进行PCR扩增,对目的基因进行克隆和测序,然后利用荧光定量PCR方法,对志贺氏菌进行检测,确定其扩增条件。建立的方法特异性强,检测的灵敏度可达到10-6 ng/μL。利用建立的方法可检测乳中2.84 cfu/mL的志贺氏菌。该方法为快速、准确检测乳中的志贺氏菌提供了参考。     

志贺氏菌实时荧光PCR检测试剂的研制

根据志贺氏菌ipaH基因序列设计了特异引物和探针,并对Taq 酶、Mg2 和引物探度等反应条件进行了优化.结果表明用实时荧光PCR法检测志贺氏茵具有特异性强、灵敏度高等突出的优点,可应用于进出口检验检疫、食品安全检测、疾病控制等领域.     

辐照与真空包装联合作用对即食食品货架期的影响

为确定辐照与真空包装联合作用对室温条件下即食食品货架期的影响,并确定杀灭食品中腐败微生物和某些非芽孢致病微生物（乙型副伤寒沙门氏菌、痢疾志贺氏菌）的最低剂量进行本研究。采用的辐照剂量分别为２．５、５、１０、２０ｋＧｙ。实验结果表明,大多数经过辐照的即食食品在室温下均可保存２年,而且一些即食食品的试样在一年后变得非常干硬。杀灭即食食品腐败微生物的最低辐照剂量为２．５ｋＧｙ。用１．０×１０２～１．０×１０４／ｇ乙型副伤寒沙门氏菌人工污染真空包装条件下的即食食品,经过５ｋＧｙ的剂量照射后,可以有效地杀灭该致病菌,并在室温条件下存放２年仍未检出沙门氏菌。在相同条件下杀灭痢疾志贺氏菌的最低辐照剂量为２．５ｋＧｙ。辐照与真空包装联合作用可有效地延长室温条件下即食食品的货架期。     

Effect of water activity (aw) and irradiation on the shelf-life of fresh noodles

In this work, the effect of water activity (a_w), irradiation and their combination on the preservation of fresh noodles was studied. Microbial growth, pH and sensory characteristics were investigated during 16 days' storage time under 37 °C. The combination of glycerol (3%), propylene glycol (2%), compound phosphate (0.4%) and salt (3%) was proved to be the most effective group which could reduce a_w from 0.979 (control) to 0.900. Under this condition, the shelf-life of fresh noodles could be extended for more than 7 times. Moreover, a synergism between humectants and irradiation treatment was observed in relation to microorganism inhibition and shelf-life extension. For all the irradiated noodles, TPC (total plate count) did never exceed the selected deterioration threshold limit (10⁶ CFU/g) during the entire observation period. When the irradiation dose was 4 kGy or higher, scarcely any bacteria proliferation was observed. Noodle samples irradiated at 4 kGy showed the best pH and sensory stability as the storage time increased.

Industrial relevance

This paper presents an effective and low-cost method to prolong the shelf-life of fresh noodles, which can largely extend the store time of fresh noodles at room temperature, and does not produce any negative changes in sensory attributes. This method will be a new system for food preservation with lots of possible industrial applications. The results of this research also have implications for dumpling skins and other noodle types.     

串珠镰刀菌辐照效应的研究

为研究γ射线在常温下对生理盐水和玉米中不同浓度串珠镰刀菌（Fusarium momiliforme）孢子的辐照杀灭效果，用不同剂量的^60Co γ射线对生理盐水和玉米中高、低2种浓度串珠镰刀菌孢子进行辐照，采用PDA培养基平板稀释法计数孢子数。γ射线辐照剂量与存活串珠镰刀菌数有明显的剂量-反应关系，生理盐水中高、低浓度串珠镰刀菌孢子试样中D10值为0．57、0．60kGy，最小杀灭剂量为4．0、3．0kGy；玉米中高、低浓度串珠镰刀菌孢子试样中D10值为0．66、0．81kGy，最小杀灭剂量为4．0、3．0kGy。γ射线对串珠镰刀菌孢子有明显的杀灭作用，4．0kGy可全部杀灭实验浓度的串珠镰刀菌孢子。     

Effect of gamma irradiation on the stability of anthocyanins and shelf-life of various pomegranate juices

Food irradiation is a process which exposing food to ionizing radiations and it can improve the safety of food. The pomegranate juice contained considerable anthocyanins and has become a new functional food available for dieting and health. In the present study, the effects of gamma irradiation (0–10 kGy) on the stability of anthocyanins and inhibition of microbial growth in pomegranate juice during storage were investigated. Results indicated that the irradiation at all applied doses, significantly reduced total and individual anthocyanins. Moreover, irradiation with higher dosages (3.5–10 kGy) had undesirable effect on the total content of anthocyanins. However, irradiation at 2.0 kGy had effectively diminished the total bacteria and fungi count and retarding microbial growth during storage. Based on adverse effect of gamma irradiation on ACs content of studied juices, it is not recommended to irradiate pomegranate juice with dosage higher than 2.0 kGy.     

辐照技术在食品工业中的应用及其发展

阐述了食品辐照技术的原理、优点及其在商业化上的应用;同时对辐照技术的发展作了展望。     

Effects of irradiation and sodium hypochlorite on the micro-organisms attached to a commercial food container

Biofilm formation on various surfaces is a well-known phenomenon and it has caused pollution, health, and safety hazards, and a substantial economic loss. The present study was to evaluate the bactericidal effects of sodium hypochlorite and gamma irradiation on Psudomonas aeruginosa, Listeria innocua, and Escherichia coli biofilm formed on polypropylene (PP), polyethylene (PET), and polycarbonate (PC), which are widely used as food container materials. The bacterial counts of all the micro-organisms tested in the bacterial suspension were decreased linearly by a gamma irradiation and 3 kGy of irradiation decreased the bacterial counts to below the detection limit (<10(1)cfu/ml). In sodium hypochlorite treated bacterial suspension only a 1 decimal point reduction in bacterial counts was observed until 100 ppm, beyond 100-400 ppm all micro-organisms tested were undetected. The microbial biofilms attached to PP, PE, and PC were very resistant to sodium hypochlorite, showing only 1-3 decimal point reductions even at 400 ppm of the total available chlorine level. In contrast, 3 kGy of gamma irradiation eliminated the micro-organisms attached to PP, PET, and PC with minor exceptions (P. aeruginosa attached to PE and Escherichia coli attached to PC). In conclusion, gamma irradiation was effective for reducing both the bacterial counts in the suspension and biofilms on PP, PET, and PC, while sodium hypochlorite was unable to eliminate the bacterial cells attached to PP, PET, and PC.     

辐照食品的卫生安全性研究和管理现状

为促进食品辐照技术的商业化应用，给我国食品辐照管理部门提供借鉴，综述了食品辐照的目的、经电离辐照加工后食品的变化、食品辐照加工的优势、食品辐照技术的历史回顾。介绍了美国、加拿大、欧盟等世界主要贸易国对辐照食品的管理和应用及其辐照方法的发展前景。辐照方法加工食品是一种安全、卫生、经济的新型技术。食品辐照技术既保护环境，又以很少的能量防止了粮食等食物的损失，还可保证食品的安全卫生。     

Changes in the colour and the acidity number of egg yolk upon irradiation

Eggs from laying hens were irradiated using radioactive Co-60 at a dose of 1 kGy, 2.5 kGy, and 5 kGy, with a dose input of 3.21 kGy h^–1. Parameters describing the colour of egg yolk such as L*, a*, and b*, were determined spectrophotometrically using the CIELAB system with the help of the portable spectrophotometer Superchroma S-Spex without gloss. The levels of all three parameters dropped upon ionizing radiation. While at a dose of 1 kGy the difference in the parameters was not statistically conclusive, after irradiation using doses of 2.5 kGy and 5 kGy, the levels of the parameters L*, a*, and b* showed a statistically conclusive decrease which was also accompanied with changes in sensorial properties such as decolouration and decreased colour. The colour of the yolk was evaluated according to the Roche scale, showing that more significant changes occurred upon irradiation at doses of 2.5 and 5 kGy (the value decreased from 6 to 5). The number of acidity estimated in egg yolk (mg KOH/g of fat) increased with the increasing dose, being conclusively higher only for doses of 2.5 kGy and 5 kGy.     

辐照对肉品微生物及牛羊肉品质的影响

研究了不同温度、不同包装形式下辐照处理对牛羊肉货架期和营养品质的影响。结果表明,产品经真空包装后,2~4.0KGy低温辐照,产品贮藏在2±1℃环境下,牛羊肉的货架期可达到60d。