Impact of intrinsic factors and storage temperature on Escherichia coli O157:H7, Salmonella enterica subsp. enterica and Listeria monocytogenes survival in fruit juices

Abstract

There is a strong trend among consumers to prefer increasingly less processed fruit juices. This raises concerns in terms of food safety, as these products may not always be free from pathogen contamination. While the low pH and the presence of antimicrobial compounds in these juices are generally considered inhibitory to pathogens, there have been occasional reports of foodborne outbreaks associated with fruit juices. However, it is important to note that the frequency of outbreaks linked to fruit juices remains significantly lower compared to other fresh produce, reflecting both the inherent properties of juices and differences in consumption patterns. The present study evaluated the survival of three different pathogens (Escherichia coli O157:H7, Salmonella enterica subsp. enterica, and Listeria monocytogenes) in persimmon, apple, peach, orange, strawberry, and red grape juices stored at 4, 15, and 25 °C, aiming to establish relationships between the food matrix and pathogen survival. Red grape and strawberry juices exhibited a sharp decline in S. enterica and L. monocytogenes populations. Conversely, orange juice was the most conducive to pathogen survival. Based on the Weibull model, L. monocytogenes exhibited δ values ≤ 0.581 ± 0.173 days in strawberry juice, while in red grape juice, the population was below 1 log₁₀ CFU/mL after inoculation. Regarding Salmonella strains, the δ values were <0.376 ± 0.244 days in strawberry juice and <0.895 ± 0.177 days in red grape juice. Of great concern is the serotype of E. coli O157:H7, as it demonstrated the highest survival trends in all fruit juices samples with the highest δ values in most cases. For instance, after 9 days, it maintained levels above 1.6 log₁₀ CFU/mL in most juices stored at 4 °C (initial populations ranged from 4.8 ± 0.1 to 5.0 ± 0.1 log₁₀ CFU/mL). In most of the analysis, physicochemical parameters, except the pH, exhibited negative correlations between pathogen populations. But in comparison, the correlations between the content of a specific polyphenol and bacterial populations were higher. For instance, after the inoculation, quercetin, kaempferol and epicatechin content presented the highest negative correlation against S. Enteritidis and both L. monocytogenes strains (between −0.936 and −0.946). The interesting finding is the strong negative correlation between the kaempferol content and all bacterial populations, not only after inoculation but also after 2 days at the three temperatures evaluated (the highest value was −0.961 against L. monocytogenes CECT 4032 at 25 °C). Pathogen levels after 2 days at 4 °C raise significant food safety concerns, given that these are typical conditions for untreated juices. Additionally, the consistent presence of E. coli O157:H7 in all juice samples throughout storage poses a significant food safety risk, as it is a leading cause of foodborne outbreaks associated with juices.