Abstract
This study aimed to investigate the effects of low-dose continuous ozone gas in controlling Listeria innocua and quality attributes and disorders of Red Delicious apples during long-term commercial cold storage. Red Delicious apples were inoculated with a three-strain L. innocua cocktail at ∼6.2 log10 CFU/apple, treated with or without 1-methylcyclopropene, and then subjected to controlled atmosphere (CA) storage with or without continuous gaseous ozone in a commercial facility for 36 weeks. Uninoculated Red Delicious apples subjected to the above storage conditions were used for yeast/mold counts and quality attributes evaluation. The 36 weeks of refrigerated air (RA) or CA storage caused ∼2.2 log10 CFU/apple reduction of L. innocua. Ozone gas application caused an additional > 3 log10 CFU/apple reduction of L. innocua compared to RA and CA storage alone. During the 36-week CA storage, low-dose continuous gaseous ozone application significantly retarded the growth of yeast/mold, delayed apple firmness loss, and had no negative influence on ozone burn, lenticel decay, russet, CO2 damage, superficial scald, and soft scald of Red Delicious apples compared to CA-alone storage. In summary, the application of continuous low-dose gaseous ozone has the potential to control Listeria on Red Delicious apples without negatively influencing apple quality attributes.
Highlights
Listeria monocytogenes can cause deadly listeriosis in susceptible human populations and has a high mortality rate (CDC, 2017)
Low-dose continuous gaseous ozone application, regardless of dose and 1-MCP treatment, dramatically increased L. innocua reduction on Red Delicious apples compared to that under refrigerated air (RA) or controlled atmosphere (CA) storage, which resulted in an additional 3.3–3.5 log10 CFU/apple reduction at the end of 24 weeks of storage followed by no further reduction during subsequent storage (Figure 1 and Table 1)
This study found a similar reduction of L. innocua on the surface of Red Delicious apples during 36 weeks of RA and CA storages
Summary
Listeria monocytogenes can cause deadly listeriosis in susceptible human populations and has a high mortality rate (CDC, 2017). Apples are grown in an open environment and can be subject to L. monocytogenes during production or subsequent postharvest packing (Angelo et al, 2017). Gaseous Ozone in Controlling Listeria on Apples apples (FDA, 2016, 2020b). These outbreaks and recalls highlight the risk of L. monocytogenes contamination of apples and the importance of controlling L. monocytogenes on apples. Apples are usually subjected to cold storage for up to 12 months in controlled atmosphere (CA) refrigerated storage. Antimicrobial interventions during this long-term storage could provide potential interventional strategies in controlling Listeria on fresh apples (Sheng and Zhu, 2021)
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