Antimicrobial Effects of Alginate-Based Films Containing Essential Oils on Listeria monocytogenes and Salmonella Typhimurium Present in Bologna and Ham

Abstract

Bologna and ham slices (300 of each) were inoculated with Salmonella Typhimurium or Listeria monocytogenes at 103 CFU/cm2. Alginate-based edible films that had been immersed in a 2 or 20% (wt/vol) CaCl2 solution and contained 1% (wt/vol) essential oils of Spanish oregano (O; Corydothymus capitatus), Chinese cinnamon (C; Cinnamomum cassia), or winter savory (S; Satureja montana) were then applied to slices to control pathogen growth. On bologna, C-based films pretreated with 20% CaCl2 were the most effective against the growth of Salmonella Typhimurium and L. monocytogenes. L. monocytogenes was the more sensitive bacterium to O-, C-, and S-based films. L. monocytogenes concentrations were below the detection level (<10 CFU/ml) after 5 days of storage on bologna coated with O-, C-, or S-based films pretreated with 20% CaCl2. On ham, a 1.85 log CFU/cm2 reduction of Salmonella Typhimurium (P ≤ 0.05) was found after 5 days of storage with C-based films regardless of the type of pretreatment used (2 or 20% CaCl2) or when coated with O-based films pretreated with 20% CaCl2. L. monocytogenes was highly resistant in ham, even in the presence of O-, C-, or S-based films. However, C-based films pretreated with 20% CaCl2 were the most effective against the growth of L. monocytogenes. Evaluation of the availability of active compounds in films revealed a significantly higher release of active compounds in C-based films (P ≤ 0.05) regardless of pretreatment or meat tested (bologna or ham). O-based films had the lowest release level of active compounds. The release of active compounds from O- and S-based films pretreated with 20% CaCl2 was faster than that in the same respective films pretreated with 2% CaCl2 regardless of the meat type. C-based film pretreated by immersion in a 20% CaCl2 solution was most efficient against both pathogens, and migration of active compounds was higher in C-based films than in O- and S-based films.