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Research Project: Elucidating the Factors that Determine the Ecology of Human Pathogens in Foods

Location: Produce Safety and Microbiology Research

Title: A review: Gaseous interventions for Listeria monocytogenes control in fresh apple cold storage

item GUAN, JIEWEN - Washington State University
item Lacombe, Alison
item RANE, BHARGAVI - Washington State University
item TANG, JUMING - Washington State University
item SABLANI, SHYAM - Washington State University
item Wu, Vivian

Submitted to: Frontiers in Microbiology
Publication Type: Review Article
Publication Acceptance Date: 10/25/2021
Publication Date: 12/9/2021
Citation: Guan, J., Lacombe, A.C., Rane, B., Tang, J., Sablani, S., Wu, V.C. 2021. A review: Gaseous interventions for Listeria monocytogenes control in fresh apple cold storage. Frontiers in Microbiology. 12. Article 782934.

Interpretive Summary: Contaminations of fresh apples with pathogenic bacteria may occur at the packing facility. The greatest risk to consumers is that there is no “kill step” included in the apple post-harvest packing process to eliminate pathogenic bacteria. In 2014, caramel apples contaminated with Listeria monocytogenes were linked to a foodborne illness outbreak. The outbreak caused 35 people to contract listeriosis and 7 deaths. This shows an urgent need to improve current food safety systems in the apple packing industry. However, there is limited systematic information about the appropriate interventions for the apple industry to review and apply. Therefore, the objective of this review is to help the apple industry identify the safety gaps with L. monocytogenes and evaluate the potential application of gaseous interventions in apple cold storage. Every year, about 4.2 billion pounds of fresh apples are stored in cold storage (33-38 °F) for up to 12 months, where apples are vulnerable to contamination with foodborne pathogens and spoilage microorganisms. An integrated approach to the existing cold storage may help to enhance safety and minimize the change of the current process. The federal agencies, the fresh apple industry, and researchers have switched their focus to gaseous interventions that decontaminate L. monocytogenes on fresh apples. This review summarizes the studies utilizing gaseous ClO2 and O3 to disinfect fresh produce. Additionally, this review discusses the regulatory requirements on gaseous interventions and organic production and handling of apples that could contribute to future industrial application and benefit the apple processors.

Technical Abstract: Listeria monocytogenes (L. monocytogenes) causes an estimated 1600 foodborne illnesses and 260 death yearly. It is a major concern for the apple industry since fresh apples can not be treated with heat-based pathogen control treatments prior to human consumption. Recent caramel apple outbreaks indicate that the current non-thermal sanitizing protocol may not be sufficient for pathogen decontamination. Federal regulations provide guidance to apple processors for sanitizer residue limits, organic production, and good manufacturing practices (GMPs). However, optimal methods to control L. monocytogenes on fresh apples still need to be determined. This review discusses L. monocytogenes outbreaks associated with caramel apples and the pathogen’s persistence in the environment. In addition, this review identifies and analyzes possible sources of contaminant for the apples during cold storage and packing. Gaseous interventions are evaluated for their feasibility for L. monocytogenes decontamination on apples in this review. For example, apple cold storage, which requires waterless interventions, may benefit from gaseous antimicrobials like chlorine dioxide (ClO2) and ozone (O3). In order to reduce the contamination risk during cold storage, significant research is still greatly needed to develop effective methods to reduce microbial loads on fresh apples. This requires commercial-scale validation of gaseous interventions and intervention integration to the current existing apple cold storage. Additionally, the impact of the interventions on final apple quality should be taken into consideration. Therefore, this review may provide apple industry suggestions to minimize the contamination risk of L. monocytogenes during cold storage and hence prevent outbreaks and reduce economic losses.