Effect of Ultraviolet Light Treatment on Microbial Reduction and Quality of Lettuce Varieties

Aiyedun, Susanna, Dixon, Ron and Onarinde, Bukola (2022) Effect of Ultraviolet Light Treatment on Microbial Reduction and Quality of Lettuce Varieties. In: IAFP 2022 Annual Meeting, July 31 - August 3, Pittsburgh, Pennsylvania.

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Item Type:Conference or Workshop contribution (Presentation)
Item Status:Live Archive


Introduction: Despite their nutritive and health benefits, leafy green vegetables (LGVs) such as lettuce have been identified as the commodity group of highest concern from a microbiological safety perspective. Hence, LGVs have been linked to serious outbreaks of infections which are caused by foodborne pathogens and their toxic compounds. Although interventions which include washing fresh produce with chemical sanitizers aim to remove pathogens, scope for improved methods for effective sanitisation are still needed especially at postharvest. Purpose: This study evaluated the potential of UV irradiation (254 nm) on microbial decontamination and quality of lettuce varieties during storage.
Methods: Sixty (60) samples including iceberg (IL), little gem (LG), romaine hearts (RH), round (RL) and sweet gem (SG) lettuce leaves were randomly spot inoculated (1 mL) with a cocktail of model foodborne pathogens (Escherichia coli ATCC 25922 and Listeria monocytogenes NCTC 11994); a population of ~8 log CFU/g. Treated samples were subjected to UV irradiation (254 nm) for 5 min, 10 min and 20 min) while untreated samples served as control. All samples were stored at 4 °C for 5 days while colour readings and pathogen levels were determined at 2-day intervals using a colorimeter and by counting bacterial growth on tryptic soy agar (TSA) plates respectively.

Results: At day 0, mean microbial reduction ranged from 0.3 to 1.8 log10 CFU/g; 0.53 to 2.1 log10 CFU/g; and 0.9 to 3.0 log10 CFU/g after UV treatment of 5 min, 10 min and 20 min respectively. Also, the order of mean microbial reduction among the lettuce varieties indicated IL<RL<SG<LG<RH. However, there was regrowth of pathogens during storage. Results (in triplicates) further revealed a slight but not significant (p > 0.05) mean reduction in the colour quality of lettuce varieties.
Significance: Results of this study suggest that UV irradiation (254 nm) is an effective tool for improving fresh produce safety. However, irregularities of surface structures can limit the exposure to UV and efficacy of decontamination.

Keywords:Ultraviolet light, Lettuce, E. coli, Listeria monotocytogenes, UVC, Leafy green vegetable
Subjects:C Biological Sciences > C510 Applied Microbiology
C Biological Sciences > C500 Microbiology
Divisions:College of Science > National Centre for Food Manufacturing
ID Code:48661
Deposited On:11 May 2022 10:32

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