Exploring the Impact of the Matrix on the Growth of Listeria monocytogenes

Abstract

Listeriosis is a significant foodborne illness mainly resulting from the consumption of food contaminated with Listeria monocytogenes. The present research aimed to comprehensively examine the growth of foodborne pathogen Listeria monocytogenes in readily accessible ultra-high temperature processed bovine milk, infant formula, and two commercial plant-based beverages (almond and coconut) stored at ambient temperature (25°C). Nutrient broth was used as a reference control. Beverage samples were inoculated with Listeria monocytogenes at approximately 9 × 10⁷ CFU/mL. The inoculated samples were stored at 25°C and sampled on the 1, 3, 6, 24, 48 and 72 hour of incubation. The findings indicate that Listeria monocytogenes was capable of proliferating in all the samples reaching the highest counts on the 48^th hour of the evaluation. Although that on the 48^th hour of evaluation, coconut beverage had the lowest bacteria counts (7.5±0.98 CFU/mL), no statistically important differences (P > 0.05) in growth rates between diverse evaluated beverages was noted. At the 72-hour incubation period, infant formula exhibited the highest microbial counts, at a value of 8 logs, whereas the coconut beverage showed the lowest microbial counts at 6 logs. The obtained data indicate that all the assessed beverages could pose a considerable threat for listeriosis, and post-opening guidelines should be thoroughly evaluated.