Abstract
Worldwide, street vending commerce has grown exponentially, representing in some countries, including Ecuador, a significant proportion of food consumed by the urban population. Pineapple is one of the common fruits sold as ready-to-eat slices by ambulant vendors in the street or on public transport at risk of contamination by various microorganisms. Previously, we selected Lactobacillus plantarum UTNCys5-4 and Lactococcus lactis subsp. lactis Gt28 strains producing peptides with high capacity to inhibit pathogen growth in vitro. In this study, the effect of different edited formulations containing a mixture of Cys5-4/Gt28 peptides was evaluated in vitro and ex vitro against a pathogenic cocktail containing E. coli (2), Salmonella (2) and Shigella (1). The growth of bacterial cocktail co-inoculated with cell-free supernatant containing peptides (formulation T1) and precipitated peptides (formulation T6), in a ratio of Cys5-4/Gt28:1:1 (v/v), results in a decrease of total cell viability with 1.85 and 1.2 log CFU/mL orders of magnitude at 6 h of incubation. About the same decrease (1.9 log CFU/g) was observed when pineapple slices artificially inoculated with the pathogenic cocktail were coated with T1 formulation, indicating the capacity to diminish simultaneous pathogens in situ, thus demonstrating its great biological control and protection. However, the E. coli cell counts reduced by 2.08 log CFU/g while Salmonella and Shigella cell counts reduced by 1.43 and 1.91 log CFU/g, respectively, at 5 days of refrigeration. In the untreated pineapple slices, the total cell density was maintained during storage, suggesting the adaptation of the pathogens to the fruit matrix. The peptide-based formulation exerted a bacteriolytic mode of action inducing pathogenic cell death. The results indicate that coating pineapple slices with peptide-based formulation is a promising approach to protect them from further contamination by microbial spoilage as well as an alternative to increase the food safety.
Highlights
Pineapple (Ananas comosus) is the third most commonly consumed fruit in Ecuador, after bananas and citrus fruits [1]
Among the five formulations having different doses of peptide released by Cys5-4 and Gt28 strains, the T1 formulation containing cell-free supernatant (CFS) Cys5-4/CFS GT28 with a ratio of 1:1 (v/v) showed a significant decrease (p < 0.05) in microbial population and 1.85 log CFU/mL order of magnitude compared to the positive control without peptide at 6 h of incubation (Figure 1)
Street food trade is a common practice in Ecuador, and this traditional practice remains a Street food trade is a common practice in Ecuador, and this traditional practice remains a considerable source of income for the local community [17]
Summary
Pineapple (Ananas comosus) is the third most commonly consumed fruit in Ecuador, after bananas and citrus fruits [1]. This perennial herbaceous fruit is produced in several provinces, including. The fruit is mainly consumed as juice, salad, or ready-to eat fresh slices or chunks [3]. Fruits provide a suitable ecosystem for microbial growth and survival; microbiological safety is of concern. Since the freshly cut chunks are perishable, they need immediate conservation treatment to reduce the microbial growth [4]. Selling foods in the street or on public transport is a cultural behavior in Ecuador. Approval and inspection of pineapple sold in this manner is basically non-existent.
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