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Microbiota of cocoa powder with particular reference to aerobic thermoresistant spore-formers

机译:可可粉的微生物群,特别是有氧耐热芽孢形成物

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The microbiological criteria of commercial cocoa powder are defined in guidelines instituted by the cocoa industry. Twenty-five commercial samples were collected with the aim of assessing the compliance with the microbiological quality guidelines and investigating the occurrence and properties of aerobic Thermoresistant Spores (ThrS). Seventeen samples complied with the guidelines, but one was positive for Salmonella, five for Enterobacteriaceae and two had mould levels just exceeding the maximum admissible level. The treatment of the cocoa powder suspensions from 100 ℃ to 170 ℃ for 10 min, revealed the presence of ThrS in 36% of the samples. In total 61 ThrS strains were isolated, of which the majority belonged to the Bacillus subtilis complex (65.6%). Strains resporulation and spore crops inactivation at 110 ℃ for 5 min showed a wide diversity of heat- resistance capacities. Amplified fragment length polymorphism analysis revealed not only a large intraspecies diversity, but also different clusters of heat-resistant spore-forming strains. The heat-resistance of spores of six B. subtilis complex strains was further examined by determination of their D and z-values. We concluded that B. subtilis complex spores, in particular those from strain M112, were the most heat-resistant and these may survive subsequent preservation treatments, being potentially problematic in food products, such as chocolate milk.
机译:商业可可粉的微生物标准在可可工业制定的指南中定义。收集了25个商业样品,目的是评估其对微生物质量指南的依从性,并调查好氧耐热芽孢(ThrS)的发生和性质。十七份样本符合指南,但沙门氏菌呈阳性,肠杆菌科为五份,霉菌含量刚好超过最大允许水平。将可可粉悬浮液在100℃至170℃下处理10分钟,发现36%的样品中存在ThrS。总共分离到61种ThrS菌株,其中大多数属于枯草芽孢杆菌复合体(65.6%)。菌株再形成和孢子在110℃下失活5 min表现出广泛的耐热能力。扩增的片段长度多态性分析不仅显示出较大的种内多样性,而且还显示了耐热芽孢形成菌株的不同簇。通过确定其枯草芽孢杆菌的D和z值,进一步检查了6种枯草芽孢杆菌复杂菌株的孢子的耐热性。我们得出的结论是,枯草芽孢杆菌复杂的孢子,尤其是来自菌株M112的孢子,最耐热,可以在随后的防腐处理中幸存下来,在食品(例如巧克力牛奶)中可能存在问题。

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