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Advisor(s)
Abstract(s)
An experiment using model ewe’s milk cheeses was designed to characterize microbial interactions that arise in actual raw
milk cheese environments. These model cheeses were manufactured according to Portuguese artisanal practices, except that the microbial load and biodiversity were fully controlled: single potential pathogens and spoilage bacteria, or a combination thereof, were combined at various initial inoculum levels in sterilized raw ewe’s milk with several lactic acid bacteria (LAB) normally found in traditional cheeses. Viable microbial counts were monitored throughout a 60-day ripening period. Two alternative mathematical approaches were used to fit the experimental data generated in terms of population dynamics: percent of inhibition and D-values. These were able to explain the complex competitive interactions between the contaminant microorganisms and the LAB adventitious populations. In general, the tested LAB were less able to inhibit contaminants present in combination and in higher concentrations. Lactococcus lactis, with its strong acidifying potential, was the most effective factor in controlling the unwanted bacterial population, especially single Staphylococcus aureus. The two lactobacilli studied, especially Lactobacillus brevis, were shown to be less effective; Escherichia coli and Listeria innocua were the contaminants least inhibited by the LAB.
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Pedagogical Context
Citation
PEREIRA, Claúdia I. - Bacterial dynamics in model cheese systems, aiming at safety and quality of portuguese-style traditional ewe’s cheeses. - Journal of Food Protection. ISSN 0362-028X . 72: 11 (2009) 2243–2251
Publisher
International Association for Food Protection