Inactivation of Listeria in Foods Packed in Films Activated with Enterocin AS-48 plus Thymol Singly or in Combination with High-Hydrostatic Pressure Treatment

Irene Ortega Blázquez,María Grande Burgos,Antonio Gálvez,Rosario Lucas,Rubén Pérez-Pulido

doi:10.3390/coatings7110204

Abstract

The aim of the present study was to determine the efficacy of films activated with enterocin AS-48 plus thymol singly, or in combination with high-hydrostatic pressure (HHP) on the inactivation of Listeria innocua in sea bream fillets and in fruit puree stored under refrigeration for 10 days. L. innocua proliferated in control fish fillets during storage. The activated film reduced viable Listeria counts in fillets by 1.76 log cycles and prevented growth of survivors until mid-storage. Application of HHP treatment to fillets packed in films without antimicrobials reduced Listeria counts by 1.83 log cycles, but did not prevent the growth of survivors during storage. The combined treatment reduced viable counts by 1.88 log cycles and delayed growth of survivors during the whole storage period. L. innocua survived in puree during storage. The activated film reduced Listeria counts by 1.80 and 2.0 log cycles at days 0 and 3. After that point, Listeria were below the detection limit. No viable Listeria were detected in the purees after application of HHP treatment singly, or in combination with the activated film. Results from the study indicate that the efficacy of activated films against Listeria is markedly influenced by the food type.

Highlights

Listeria monocytogenes is a psychrotrophic foodborne Gram-positive bacterium which is widely found in the environment, such as in plants, soil, animal, water, dirt, dust, and silage [1,2]
For the controls, viable Listeria counts already increased by day 5, and were significantly higher (p < 0.05) by 1.7 log cycles at the end of storage period
Results from the present study indicated that, under acidic pH condition, L. innocua was much more sensitive to treatment with activated films containing enterocin AS-48 and thymol and to high-hydrostatic pressure (HHP) treatment compared to results obtained on sea bream fillets having a pH value close to neutrality

Summary

Introduction

Listeria monocytogenes is a psychrotrophic foodborne Gram-positive bacterium which is widely found in the environment, such as in plants, soil, animal, water, dirt, dust, and silage [1,2]. In the EU, there was a statistically significant increasing trend of listeriosis over 2008–2015, with a case fatality of 17.7% [3]. Ready-to-eat (RTE) fish and other fishery products showed the highest percentages of non-compliance at retail, followed by other foods of animal origin, such as meats and dairy products [3]. L. monocytogenes was reported in vegetables, fruits, and fruit puree [3]. Consumption of fruits and vegetables contaminated with L. monocytogenes resulted in outbreaks of listeriosis [4,5]. It is of the utmost importance to reduce the risks for transmission of this bacterium through the food chain

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