冷链条件下气调包装酱卤鸭肉制品货架期预测模型的建立

目的 以气调包装酱卤鸭肉制品为研究对象,在冷链温度范围内建立一套准确、高效的货架期预测模型。方法 利用选择性培养基测定不同温度下产品各微生物数量,确定4~25℃条件下产品优势腐败菌。对乳酸菌数量与感官评定值进行了回归分析确定最小腐败量Ns。分别采用修正的Gompertz方程和平方根方程建立一、二级模型,并通过预测值与实测值对比验证模型的可靠性。结果 确定了4~25℃条件下产品优势腐败菌为乳酸菌,最小腐败量Ns=6.14(lg(cfu /g))。一、二级模型拟合度均良好,三种温度下模型预测值与实际值间的差异均在30％左右,波动幅度在10%以内。结论 实现了对4~25℃内任何时间点产品剩余货架期的预测,为冷链条件下气调包装酱卤鸭肉制品品质的变化提供了理论指导。     

水基(乳液)胶粘剂微生物污染及其罐内防腐效果测试

对广东省部分水基(乳液)胶粘剂生产企业微生物污染的来源和种群进行了调查,建立以微生物攻击挑战性试验来快速判定水基(乳液)胶粘剂罐内防腐效果的评价方法,探索该类胶粘剂微生物污染的有效防治技术。     

迭香精油活性贴对鲜切猪肉保鲜效果的研究

目的 为了提高迷迭香精油(REO)的稳定性,开发出一种安全、便捷的实用型活性包装。方法 以迷迭香精油为活性成分,采用三步法(乳化、包埋、多层复合)制备出精油缓释活性贴,并验证其对鲜切猪肉的保鲜效果。结果 在4 ℃下,不同比例的迷迭香精油活性贴均可在一定程度上抑制鲜切猪肉的腐败变质,最佳处理效果的体积比为4∶6,贮藏至第6天时,猪肉的pH值、挥发性盐基氮(TVB–N)含量、硫代巴比妥酸(TBARS)值较空白对照(CK)分别降低了0.7 mg/g、0.073 1 mg/g、0.63 mg/kg;延缓了猪肉色度、汁液流失率、菌落总数(TVC)、感官品质的变化,可延长鲜切猪肉货架期2 d左右。结论 制备的缓释型活性贴具有稳定性好、操作简单易行的优势。作为绿色、可生物降解的包装材料,在食品保鲜领域具有潜在的应用价值。     

干浆米线的变质微生物及其污染源分析

以某米线生产企业生产的变质干浆米线为研究对象,对其进行变质微生物检测及其污染源分析。研究表明:4份样品的微生物数量非常高,细菌总数在106—108cfu/g,霉菌数量在104cfu/g,酵母为103—104cfu/g。从微生物组成来看,细菌则主要是葡萄球菌属(Staphylococcus spp.),为凝固酶阴性,其可能来自操作人员体表或设备。霉菌主要是拟青霉(Paecilomyces spp.)、毛霉(Mucor spp.)、白地霉(Geotrichum candidum)和交链孢霉(Alternaria spp.);菌相组成与空气中主要的霉菌菌相一致,显示该污染的源头可能是空气。干浆米线虽经干燥,但水分活度不够低,易染菌,保质期短;在保鲜、干燥工艺上还待研究和改进。     

Microbial Diversity of Ground Beef Products in South Korean Retail Market Analyzed by PCR-DGGE and 454 Pyrosequencing

The purpose of this study was to assess the microbial community in ground beef purchased from local stores in the north central area of South Korea. A total of 31 ground beef samples showed 3.77 ± 5.16 × 10⁵ CFU/g on aerobic plate counts, and PCR-based denaturing gradient gel electrophoresis was performed to assess the microbial community, which revealed a diverse profile among the products. Four of these samples were selected for further analyses via 454 pyrosequencing. Pseudomonas was the most frequently identified genus in terms of relative abundance (4.54–73.8%), and other bacteria such as Lactobacillus, Acinetobacter, and Carnobacterium were also identified in the ground beef. The presence of bacteria can affect the spoilage of ground beef products depending on the microbial populations, and understanding these populations may help limit spoilage and/or foodborne illness. This study illustrates the microbial diversity occurring among Korean ground beef products, even within a local region, and provides a molecular approach for potential ground beef microbial quality assessment.     

Susceptibility of Escherichia coli O157 to chitosan‐arginine in beef liquid purge is affected by bacterial cell growth phase

Here, we evaluated the impact of bacterial growth stage on the effect of chitosan‐arginine (Ch‐arg) on Escherichia coli O157:H7 cell numbers and metabolic activity within contaminated beef juice held at room temperature. Using a lux‐marked metabolic reporter strain of E. coli O157:H7, the results showed that Ch‐arg was most bioactive against cells in the lag phase and exponential phase. In comparison, there was a reduced, although still significant, inhibitory effect of Ch‐arg on the viability and metabolic activity of E. coli O157 held in stationary phase. Ch‐arg reduced, but did not eliminate E. coli O157 growth in the meat juice over 48 h. Based on the evidence presented here and elsewhere, we conclude that Ch‐arg can limit the growth and activity of food spoilage bacteria; however, it cannot completely eliminate bacterial contaminants originally present. Ch‐arg should therefore be viewed as a potentially protective measure rather than a biocidal agent that completely eliminates the risk of pathogen transfer in the food chain.     

Spoilage of refrigerated (4 °C) Litopenaeus vannamei: cooperation between Shewanella species and contribution of cyclo‐(L‐Pro‐L‐Leu)‐dependent quorum sensing

The spoilage potential of Shewanella putrefaciens and S. baltica isolated from spoiled refrigerated Litopenaeus vannamei was evaluated by in vitro assays for trimethylamine oxide reduction, extracellular hydrolytic enzymes and biofilm formation, and in vivo inoculation into surface‐sterilised shrimp followed by microbial, biochemical and sensory analyses during storage for 5 days at 4 °C. S. baltica displayed higher spoilage potential than S. putrefaciens both in vitro and in vivo. Shrimp co‐inoculated with them had one‐day shorter shelf life than those mono‐inoculated, based on the results of bacterial density, volatile base nitrogen, trimethylamine, volatile organic compounds and sensory analysis, which strongly suggests cooperation of Shewanella species in shrimp spoilage. Exogenous cyclo‐(L‐Pro‐L‐Leu) boosted bacterial growth, extracellular protease and collagenase activities, and biofilm formation of S. putrefaciens and S. baltica at least before they entered the stationary phase, indicating that cyclo‐(L‐Pro‐L‐Leu)‐dependent quorum sensing, a recently suggested communication mechanism between them, contributes to the cooperation.     

The ability of zinc to inhibit the sporulation and viability of Clostridium sporogenes and growth of other bacteria

The objective of this study was to investigate the influence of zinc on the sporulation and viability of Clostridium sporogenes and on the growth of other bacteria. When 0.5% ZnCl₂ was added to a sporulation medium, it completely inhibited C. sporogenes (PA 3679) sporulation for up to 3 weeks. At concentrations of 0.5% and 1.0%, ZnCl₂ not only completely inactivated the vegetative cell viability (>7.0 Log reduction) but also significantly reduced the spore viability (<2.1 Log reduction) of C. sporogenes. Taken together, it was concluded that zinc blocks C. sporogenes sporulation by damaging (or killing) vegetative cells and probably by interfering with the biosynthesis of spore components. In addition to the inhibitory effect on the sporulation and viability of C. sporogenes, ZnCl₂ was found to have a broad antimicrobial spectrum against all Gram‐positive and Gram‐negative spoilage and pathogenic bacteria tested. The minimal inhibitory concentration for inhibiting the bacteria ranged between 3.7 and 7.4 mm . Therefore, we expect that this compound or a combination thereof has a potential as a surface‐cleaning agent or disinfectant.