Industrial-scale application of bacteriophages on baby spinach: One-year study of Listeria control, quality and microbial community shifts.
María Isabel Gil, Juan Antonio Tudela, Guillermo Illán, Natalia Hernández, Silvia Andújar, Diego Sabater +2 more
Food research international (Ottawa, Ont.)
Abstract
Bacteriophages have emerged as promising biocontrol agents against pathogenic bacteria due to their strong antimicrobial activity and host specificity. In this study, we evaluated a previously validated industrial bacteriophage cocktail (PhageGuard Listex™) for its performance on baby spinach, focusing on product quality and microbial community dynamics. Twenty industrial trials conducted over one year compared non-treated and phage-treated baby spinach samples after processing (day 0) and after 10 days of storage under commercial (3 d at 4 °C followed by 7 d at 7 °C) and abusive (continuous 10 °C) temperature conditions. Phage stability was confirmed in the application solution and persistence on the product surface after storage. Although Listeria monocytogenes was not detected in any sample (0/600), the proportion of samples positive for Listeria spp. was significantly lower in the phage-treated group (6%) than in the non-treated group (12%). The preventive phage application did not affect headspace gas composition, sensory attributes, or objective color parameters. Quality deterioration was observed only at 10 °C, regardless of phage treatment. Despite the reduction in Listeria spp. prevalence, microbial diversity and community structure were unaffected by phage application, consistent with the low relative abundance of Listeria spp. in the microbiota and the narrow host range of the phage cocktail; storage conditions, particularly temperature, were the most influential factor affecting bacterial taxonomic composition. The relative abundance of Pseudomonas and Flavobacterium increased during storage, while Bacillus and Exiguobacterium decreased. These findings support the feasibility of using this bacteriophage-based treatment as a preventive intervention that does not affect product quality and preserves the natural microbial ecology of baby spinach during storage.