Assessing the growth ofEscherichia coliO157:H7 andSalmonellain spinach, lettuce, parsley and chard extracts at different storage temperatures

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Abstract

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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