Control of Listeria monocytogenes in ready-to-eat meats containing sodium levulinate, sodium lactate, or a combination of sodium lactate and sodium diacetate

ABSTRACT:  This study investigated the use of sodium levulinate to prevent outgrowth of Listeria monocytogenes in refrigerated ready-to-eat (RTE) meat products. Turkey breast roll and bologna were formulated to contain 1%, 2%, or 3% (w/w) sodium levulinate, 2% sodium lactate, a 2% combination of sodium lactate and sodium diacetate (1.875% sodium lactate and 0.125% sodium diacetate), or no antimicrobial (control). Samples of the RTE products were sliced, inoculated with 10² to 10³ CFU/cm² of a 5-strain cocktail of L. monocytogenes , vacuum packaged, and stored at refrigeration temperature for 0 to 12 wk. Counts reached 10⁸ CFU/cm² on control turkey roll product after 8 wk, and over 10⁷ CFU/cm² on control bologna after 12 wk. Addition of 2% or more sodium levulinate to turkey roll and 1% or more sodium levulinate to bologna completely prevented growth of L. monocytogenes during 12 wk of refrigerated storage. A consumer taste panel with pathogen-free samples found no differences in the overall liking among the preparations of turkey roll or among preparations of bologna. These results show that sodium levulinate is at least as effective at inhibiting outgrowth of L. monocytogenes in RTE meat products as the current industry standards of lactate or lactate and diacetate, and levulinate addition does not alter the overall liking of the RTE meat products.     

Survival of Listeria monocytogenes, Listeria innocua, and Lactic Acid Bacteria in Chill Brines

ABSTRACT:  Listeria monocytogenes is the pathogen of concern in ready-to-eat (RTE) meat products. Salt brines are used to chill processed meats. L. monocytogenes and lactic acid bacteria (LAB) can grow under saline conditions, and may compete with each other for nutrients. The objective of this study was to determine the effect of lactic acid bacteria ( Enterococcus faecalis , Carnobacterium gallinarum , and Lactobacillus plantarum ) on the survival of L. monocytogenes and Listeria innocua in brines stored under low temperatures for 10 d. Sterile tap water (STW) and 2 brine solutions (7.9% and 13.2% NaCl) were inoculated with 1 of 5 cocktails ( L. monocytogenes , L. innocua , LAB, L. monocytogenes + LAB, or L. innocua + LAB) at initial concentrations of 7 log CFU/mL. Brines were stored for 10 d at 4 or 12 °C. Three replications of each brine concentration/cocktail/temperature combination were completed. No significant reductions of L. monocytogenes occurred in 7.9%[w/v] or 13.2%[w/v] brines when LAB were present; however, there were significant reductions after 10 d of L. monocytogenes in the STW solution when LAB were present (1.43 log CFU/mL at 4 °C and 3.02 log CFU/mL at 12 °C). L. innocua was significantly less resilient to environmental stresses of the brines than L. monocytogenes , both with and without LAB present ( P ≤ 0.05). These strains of lactic acid bacteria are not effective at reducing L. monocytogenes in brines at low temperatures. Furthermore, use of L. innocua as a model for L. monocytogenes is not appropriate under these environmental conditions.     

食品中单核增生性李斯特菌的PCR快速检测研究

为提高食品中单增李斯特菌的检测水平,针对单增李斯特菌中多个稳定的特异性基因hlyA、plcB、prfA、iap,设计并筛选出7对引物组成多重-巢式PCR联合检测体系,并结合高灵敏性的聚丙烯酰胺凝胶电泳,对单增李斯特菌进行快速检测,多重PCR的灵敏度达到1×102CFU ml,巢式PCR的灵敏度达到1×10CFU ml。结果表明该检测体系具有快速可靠、灵敏准确及特异性好的特点,而且有效缩短了检验周期,从传统的7～14d缩短到1～2d。     

Inhibition of Listeria monocytogenes by exposure to a combination of nisin and cold-pressed terpeneless Valencia oil

Listeria monocytogenes is an important foodborne pathogen and its control in foods is a significant challenge. This study evaluated the effectiveness of nisin and cold-pressed terpeneless Valencia oil (CPTVO) on limiting L. monocytogenes growth. Disk diffusion assays were performed to determine the effects of CPTVO and nisin individually and in combination. Together, these antimicrobials produced a zone of inhibition that was significantly larger (P < 0.05) than zones correlating to CPTVO or nisin individually. Furthermore, L. monocytogenesΔsigB had an increased sensitivity to the combination treatment. Growth experiments performed in brain heart infusion (BHI) broth revealed the effects of nisin and CPTVO, individually and in combination on L. monocytogenes growth rate. When L. monocytogenes was grown in BHI containing 0.025% CPTVO and 26 IU/mL nisin, no growth inhibition was observed relative to the control. However, exposure to CPTVO at 0 h followed by the introduction of nisin at 15 h resulted in a statistically significant (P < 0.05) reduction in growth. This approach to inhibiting L. monocytogenes has potential as an all-natural, generally-recognized-as-safe multiple hurdle intervention that may be applicable for ready-to-eat products in which L. monocytogenes is likely to cause foodborne illness.     

肉中单核细胞增生李斯特菌PCR快速检测方法建立

目的:建立单核细胞增生李斯特菌(Listeria monocytogenes,LM)快速、敏感、特异的PCR诊断方法。方法:采用聚合酶链式反应技术(PCR)特异性扩增单核细胞增生李斯特菌内化素基因(ivlA),并评价该方法的特异性与敏感性。结果:在445bp处出现inlA基因的目的片断,只有单增李斯特菌的目的片段获得扩增,其他菌种扩增均呈阴性;该方法可以检测到DNA的检测限。结论:PCR方法比传统细菌检测方法更特异、快速、灵敏和简便;为肉中单增李斯特菌的快速检测提供了新的手段。     

单核细胞增生李斯特氏菌食品分离株协同 溶血现象研究

目的对从食品中分离的88株单核细胞增生李斯特氏菌(Listeria monocytogenes)进行协同溶血(christie,atkins and munch-petersen,c AMP)测试。方法根据食品安全国家标准食品微生物学检验单核细胞增生李斯特氏菌检验GB 4789.30-2010的方法进行c AMP测试。结果所测试的88株单核细胞增生李斯特氏菌分离株与GB 4789.30中描述的结果一致,即在靠近金黄色葡萄球菌(Staphylococcus aureus)的接种端溶血增强,78株靠近马红球菌一端呈阴性反应。同时,发现10株分离株c AMP测试结果与传统的测试结果不同,在靠近马红球菌(Rhodococcus equi)的接种端溶血增强。结论对88株单核细胞增生李斯特氏菌分离株c AMP测试结果表明,有大约11%的菌株在靠近马红球菌的接种端溶血增强。     

Inhibition of Listeria monocytogenes and Salmonella by Combinations of Oriental Mustard,Malic Acid,and EDTA

The antimicrobial activities of oriental mustard extract alone or combined with malic acid and EDTA were investigated against Salmonella spp. or Listeria monocytogenes at different temperatures. Five strain Salmonella or L. monocytogenes cocktails were separately inoculated in Brain Heart Infusion broth containing 0.5% (w/v) aqueous oriental mustard extract and incubated at 4 °C to 21 °C for 21 d. For inhibitor combination tests, Salmonella Typhimurium 02:8423 and L. monocytogenes 2–243 were individually inoculated in Mueller Hinton broth containing the mustard extract with either or both 0.2% (w/v) malic acid and 0.2% (w/v) EDTA and incubated at 10 °C or 21 °C for 10 to 14 d. Mustard extract inhibited growth of the L. monocytogenes cocktail at 4 °C up to 21 d (2.3 log₁₀ CFU/mL inhibition) or at 10 °C for 7 d (2.4 log₁₀ CFU/mL inhibition). Salmonella spp. viability was slightly, but significantly reduced by mustard extract at 4 °C by 21 d. Although hydrolysis of sinigrin in mustard extract by both pathogens was 2 to 6 times higher at 21 °C than at 4 °C to 10 °C, mustard was not inhibitory at 21 °C, perhaps because of the instability of its hydrolysis product (allyl isothiocyanate). At 21 °C, additive inhibitory effects of mustard extract with EDTA or malic acid led to undetectable levels of S. Typhimurium and L. monocytogenes by 7 d and 10 d, respectively. At 10 °C, S. Typhimurium was similarly susceptible, but combinations of antimicrobials were not more inhibitory to L. monocytogenes than the individual agents.     

熟肉制品中单核细胞增生李斯特氏菌耐药及致病的遗传分析

目的 获得中国不同省份熟肉制品中的33株单核细胞增生李斯特氏菌(单增李斯特菌)的抗生素敏感性特征图谱,并运用全基因组测序对菌株进行耐药和致病的基因遗传分析.方法 采用微量肉汤稀释法对33株熟肉制品中的单增李斯特菌进行药敏测定,同时进行高精度框架图测序,基因组序列经组装后通过相应的生物信息学流程进行数据分析.结果 33株...     

食品中单核细胞增生李斯特氏菌检测能力验证

目的通过能力验证提升食品中单核细胞增生李斯特氏菌检测能力和实验室质量管理水平。方法依据GB 4789.30-2010《食品安全国家标准食品微生物学检验单核细胞增生李斯特氏菌检验》进行检测,利用BAX system Q7全自动病原微生物检测系统对能力验证中的3个样品进行快速筛查,采用VITEK2COMPACT全自动细菌鉴定系统、基质辅助激光解析电离飞行时间质谱(matrix-assisted laser desorption ionization time-of-flight mass spectrometry,MALDI-TOF-MS)和溶血素O基因(hlyA)序列比对分析鉴定可疑菌株。结果编号CODE1和CODE3的样品检出单核细胞增生李斯特氏菌,编号CODE2的样品未检出。结论本实验室参加了中国食品药品检定研究院组织的食品中单核细胞增生李斯特氏菌检测能力验证测试,取得了满意的实验结果。     

2010~2016年云南省熟肉制品和餐饮食品中单增李斯特菌污染情况调查分析

目的 了解2010～2016年云南省市售熟肉制品和餐饮食品中单增李斯特菌污染情况调查分析。方法 在全省16个州市县中选取超市、农贸市场、零售及餐饮环节等为采样点, 随机采取熟肉制品1465份和餐饮食品3674份, 按照GB 4789.30-2010《食品安全国家标准 食品微生物学检验 单核细胞增生李斯特氏菌检验》及《全国食源性致病菌监测工作手册》进行检测和鉴定。结果 1465份熟肉制品中单增李斯特菌检出率为2.18%(32/1465), 3674份餐饮食品中单增李斯特菌阳性率为1.44%(53/3674)。在不同流通环节中, 熟肉制品和餐饮制品中检出率最高的分别为便利店和超市, 分别为9.09%(5/55)和1.67%(3/180)。在不同的监测地区, 熟肉制品和餐饮制品检出率最高均为昭通地区, 分别为7.8%(11/141)和7.17%(18/251)。结论 单增李斯特菌在熟肉制品及餐饮食品中均有检出, 说明云南省的食品中存在一定的单增李斯特菌污染, 对消费者的安全有潜在风险, 相关监管部门应持续加强监管, 预防食源性疾病的发生。     

食品中单增李斯特菌快速检测技术研究进展

单核细胞增生性李斯特氏菌(简称单增李斯特菌)是一种广泛存在于自然界中可导致人畜共患病的病原菌, 同时也是一种常见的食源性致病菌。目前, 食品中单增李斯特菌的检测主要采用国标法, 传统检验方法虽然可操作性高, 但检验流程耗时过长。随着生活水平不断提高, 人们在饮食中摄入受单增李斯特菌污染的食品的风险增大, 如遇到食品安全突发事件, 传统检测不能及时得到检测结果, 无法保障人们的饮食安全。本文概述了基于分子生物学和免疫学发展起来的快速检测方法, 包括PCR法、实时荧光定量PCR法、环介导等温扩增法、酶联免疫吸附法、免疫层析试纸条, 其中环介导等温扩增法已经应用于食品致病菌的检测。通过分析对比以上快速检测方法, 为探索更灵敏高效且适用于基层食品检验的检测方法提供参考。     

D and z Values of Salmonella, Listeria innocua, and Listeria monocytogenes in Fully Cooked Poultry Products

: The D and z values of Salmonella, Listeria innocua, and Listeria monocytogenes were obtained for different ready‐to‐eat poultry products, including chicken, turkey, and duck. The D values of Salmonella, L. innocua, and L. monocytogenes were 151.5 to 0.1 min at 55 to 70°C, and the z values of Salmonella, L. innocua, and L. monocytogenes were 4.9 to 7.0 °C. Significant differences were found for the heat resistance of Salmonella, L. innocua, and L. monocytogenes among turkey, duck, and chicken products, indicating that the kinetic values of a certain pathogen in a specific product should be used for determining process lethality in fully cooked and vacuum‐packaged poultry products during post‐cook heat treatments.     

即食食品中单增李斯特菌的半定量风险评估

开展某市即食食品中单增李斯特菌的半定量风险评估,参照微生物风险评估程序,对单增李斯特菌开展了危害识别、危害特征描述、暴露评估和风险特征描述。通过剂量反应关系推测易感人群和非易感人群由于摄入即食食品导致单增李斯特菌病的每年发病概率分别为3.71×10-7和3.39×10-9。基于2008~2011年监测各类生食蔬菜、生食水产品、菜肴(沙拉)等即食食品942组数据,构建了即食食品中单增李斯特菌的风险矩阵,由风险可能性和风险损失度计算得到易感人群通过摄入即食食品感染单增李斯特菌的风险等级属于五级风险等级中较小的一级,表明当地居民通过摄入即食食品感染单增李斯特菌病的风险较小。本文可为构建完整单增李斯特菌风险评估体系提供理论参考。     

实时定量荧光PCR快速鉴定食品中单核细胞增生李斯特氏菌

目的建立实时定量荧光PCR法(real-time PCR)快速鉴定食品中的单核细胞增生李斯特氏菌(Listeria monocytogenes,LM)。方法选取2016年国家食品风险监测样本134例与模拟灭活LM样本10例,采用GB/T4789.30-2010与real-time PCR方法同步检测单核细胞增生李斯特菌。结果共检测食品134份,包括肉制品、水产品、快餐和即食食品等。共检出8株LM,检出率为5.97%。以GB/T4789.30-2010为金标准判断,real-time PCR方法检测样本中LM的灵敏度与特异度均达到100%。模拟灭活LM样本real-time PCR方法检出率为100%,标准法检出率为0%。结论本方法可以简化实验程序,减少工作量,节约检测试剂,为可能发生的食物中毒尽早提供实验依据。     

即食食品中单增李斯特氏菌快速检测技术的研究进展

单核细胞增生李斯特氏菌引发的食品安全事件被广泛关注,它不仅会导致疾病的发生,严重时甚至还会引起感染者死亡,所以即食食品中单增李斯特菌的快速检测技术显得至关重要。本文阐述了不同地区的即食食品中单增李斯特菌的污染率,并综合分析了分子生物学方法、免疫学检测方法、生物传感器检测方法、光谱学检测方法等优缺点以及发展现状,为研发新型快检技术提供新思路。     

肽核酸荧光原位杂交技术快速检测食品中的李斯特菌属及单增李斯特菌

目的建立利用肽核酸荧光原位杂交技术(PNA-FISH)快速检测食品中李斯特菌属及单增李斯特菌的方法。方法针对李斯特菌属、单增李斯特菌分别设计合成2份PNA探针lis-16S-1、lm-16S-2,并建立荧光原位杂交技术,优化杂交条件,对选取的13株李斯特菌和其他9株非李斯特菌进行检测,验证探针的特异性和灵敏度,并对118份食品样品用LB肉汤2次增菌培养后进行PNA-FISH检测。结果探针灵敏度和特异性均为100%,从118份食品中检出14株李斯特菌和8株单增李斯特菌,结果与API方法和VITEK方法鉴定结果一致。结论 PNA-FISH方法可靠易行,对从食品中检测致病性单增李斯特菌有较高的实用性。     

绿色魏斯氏菌发酵液对单核细胞增生李斯特菌的抑制及其在冷却猪肉保鲜中的应用

采用微量肉汤稀释法测定绿色魏斯氏菌(Weissella viridescens)发酵液对单核细胞增生李斯特菌(Listeria monocytogenes,Lm)的最小抑菌浓度,微孔板法结合显微镜观察检测绿色魏斯氏菌发酵液对Lm生物被膜形成的影响,最后通过测定冷藏过程中冷却猪肉的菌落总数、Lm总数、感官指标和理化指标评...     

Gamma irradiation as a means to eliminate Listeria monocytogenes from frozen chicken meat

Cells of Listeria monocytogenes ATCC 35152 were sensitive to gamma irradiation in phosphate buffer, pH 7.00 (D₁₀, dose required for 10% survival—0.15 kGy) at 0–5°C. The cells showed higher radiation survival when irradiated under frozen condition, with a D₁₀ of 0.3 kGy. The protection offered by shrimp/chicken/kheema homogenates (100 g litre^?1) was evidenced by even higher D₁₀ values (0.5 kGy) at both 0–5°C and cryogenic temperature. Boneless chicken meat samples were artificially inoculated with L monocytogenes ATCC 35152 cells at low (5 × 10³) colony-forming unit (cfu) g^?1 and high (5 × 10⁶ cfu g^?1) concentrations and irradiated at 1, 3, 4, 6 kGy doses under cryogenic conditions. The efficacy of the radiation process was evaluated by detecting L monocytogenes during storage at 2–4°C in the irradiated samples. These studies, when repeated with three other serotypes of L monocytogenes, clearly suggested the need for a dose of 3 kGy for elimination of 10³ cfu cells of L monocytogenes g^?1 from air-packed frozen chicken meat.     

温度及乳酸链球菌素对单增李斯特菌的抑制作用

通过Matlab软件拟合Gompertz生长模型,研究了温度对单增李斯特菌(Listeria.monocytogenes,LM)的影响;同时,研究了不同浓度(5、10、50、100、150μg/m L)、p H(1、3、5、7、9)、温度(45、75、95、115、121℃)条件下的乳酸链球菌素对LM杀菌活性的影响,旨在为LM的监控技术发展提供理论依据。结果表明:低温的抑制效果明显,最大细胞密度减少了4.3455 lg cfu/m L;乳酸链球菌素浓度低于5μg/m L时能促进LM的生长,高于10μg/m L时,对LM有一定的杀菌作用,高于150μg/m L时,48 h之内几乎可以杀死营养肉汤中的所有LM;乳酸链球菌素对酸性有协同效应;并有较好的热稳定性。