Assessing the growth of Escherichia coli O157:H7 and Salmonella in spinach, lettuce, parsley and chard extracts at different storage temperatures
2016
Posada‐Izquierdo, G. | Del Rosal, S. | Valero, A. | Zurera, G. | Sant'Ana, A.S. | Alvarenga, V.O. | Pérez‐Rodríguez, F.
AIMS: The objective of this work was to study the growth potential of Escherichia coli O157:H7 and Salmonella spp. in leafy vegetable extracts at different temperature conditions. METHODS AND RESULTS: Cocktails of five strains of E. coli O157:H7 and of Salmonella enterica were used. Inoculated aqueous vegetable extracts were incubated at 8, 10, 16 and 20°C during 21 days. Microbial growth was monitored using Bioscreen C®. In spinach extract, results showed that for E. coli O157:H7 and Salmonella significant differences (P < 0·05) for μₐbₛ (maximum absorbance rate) were obtained. For both pathogens, growth in chard was slightly lower. In contrast, iceberg lettuce and parsley showed the lowest values of μₐbₛ, below 0·008 h⁻¹. The coefficients of variance (CoV) calculated for the different replicates evidenced that at low temperature (8°C) a more variable behaviour of both pathogens is expected (CoV > 180%). CONCLUSIONS: This study provides evidence that aqueous extracts from vegetable tissues can result in distinct growth niche producing different response in various types of vegetables. SIGNIFICANCE AND IMPACT OF THE STUDY: Finally, these results can be used as basis to establish risk rankings of pathogens and leafy vegetable matrices with relation to their potential growth.
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