Possible Sources of Listeria monocytogenes Contamination of Fresh-cut Apples and Antimicrobial Interventions During Antibrowning Treatments: A Review

Fresh-cut apples, being rich in antioxidants and other nutrients, have emerged as popular snacks in restaurants, at home, and in school lunch programs, partially due to freshness, convenience, and portion size availability. Two major challenges in processing fresh-cut apples are the browning of cut surfaces and contamination with human pathogens. Regarding human pathogens, contamination by Listeria monocytogenes is a major concern, as evidenced by two outbreaks of whole apples and numerous recalls of fresh-cut apples. Antibrowning agents currently used by the industry have little to no antimicrobial properties. The present review discusses the possible origins of L. monocytogenes in fresh-cut apples, including contaminated whole apples, and contamination via the processing environment and the equipment in fresh-cut facilities. Treatment with antibrowning solutions could possibly be an opportunity for Listeria contamination and represents the last chance to inactivate pathogens. The discussion is focused on the antibrowning treatments where formulations and coatings with antibrowning and antimicrobial properties have been developed and evaluated against Listeria and other microorganisms. In addition, several research needs and considerations are discussed to further reduce the chance of pathogen contamination on fresh-cut apples.