Antifungal activity of alginate coatings with essential oil of Mexican oregano incorporated in the stem of tomatoes

Abstract

SummaryAdding natural antimicrobials such as essential oils (EOs) to alginate coatings on fruits provides an antifungal effect and a semipermeable water vapour barrier. This work aims to evaluate the antifungal effect of Lippia berlandieri S. (Mexican oregano) EO incorporated into alginate to coat tomato stems inoculated with Penicillium commune, Fusarium spp., or Cladosporium herbarum. Alginate films and coatings with EO concentrations (0%, 0.25%, 0.75%, 1%, 2%, or 4% v/v) were prepared to evaluate their properties (physical, mechanical, and water vapour transmission rates) as well as their effect on mould growth on tomato stems for 28 days during refrigerated storage. Mould growth was described with probabilistic and time‐to‐growth predictive models. Two treatment types were assessed (tomato inoculated and coated, TIC, and tomato coated and inoculated, TCI) to provide information about the moment of mould contamination (before or after coating). EO concentration influenced the alginate films' physical, mechanical, and barrier properties. Testing the coatings against moulds revealed varying inhibitory effects. Fusarium spp. exhibited the highest resistance, while C. herbarum was the most susceptible. The predictive models appropriately described the probability of growth or the time‐to‐growth of the studied moulds, identifying critical concentrations of oregano EO needed to inhibit mould growth effectively. The findings suggest that alginate coatings with oregano EO can serve as a natural and effective antifungal treatment for tomatoes, offering insights into optimal concentrations and application methods for extended shelf life.