Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 406783
Title Microbiota of cocoa powder with particular reference to aerobic thermoresistant spore-formers
Author(s) Líma, L.J.R.; Kamphuis, H.J.; Nout, M.J.R.; Zwietering, M.H.
Source Food Microbiology 28 (2011)3. - ISSN 0740-0020 - p. 573 - 582.
DOI http://dx.doi.org/10.1016/j.fm.2010.11.011
Department(s) Food Microbiology Laboratory
VLAG
Publication type Refereed Article in a scientific journal
Publication year 2011
Keyword(s) bacillus-subtilis - heat-resistance - sp-nov - aflp - heterogeneity - bacteria - sequence - strains - milk - rna
Abstract 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 °C to 170 °C 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 °C 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
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