Enhanced bactericidal activity of enterocin AS-48 in combination with essential oils, natural bioactive compounds and chemical preservatives against Listeria monocytogenes in ready-to-eat salad

Enterocin AS-48 (30-60 microg/g) significantly reduced viable counts of Listeria monocytogenes in Russian-type salad during one week storage at 10 degrees C. Antilisterial activity of AS-48 (30 microg/g) in salad was strongly enhanced by essential oils (thyme verbena, thyme red, Spanish oregano, ajowan, tea tree, clove, and sage oils tested at 1%, as well as with 2% rosemary oil). Antilisterial activity also increased in combination with bioactive components from essential oils and plant extracts, with other related antimicrobials of natural origin or derived from chemical synthesis (carvacrol, eugenol, thymol, terpineol, tyrosol, hydroxytyrosol, caffeic, ferulic and vanillic acid, luteolin, geranyl butyrate, geranyl phenylacetate, pyrocatechol, hydrocinnamic acid, tert butylhydroquinone, phenylphosphate, isopropyl methyl phenol, coumaric acid, and 2-nitropropanol), and with food preservatives (citric and lactic acid, sucrose palmitate, sucrose stearate, p-hydroxybenzoic methylester acid -- PHBME, and Nisaplin). AS-48 acted synergistically with citric, lactic acid, and PHBME. A mixed population of two L. monocytogenes strains was markedly reduced for one week in salads treated with AS-48 (30 microg/g) in combination with lactic acid, PHBME or Nisaplin. The increased bactericidal activity of these combinations is interesting to improve protection against L. monocytogenes during salad storage.