Submitted to: Journal of Radiation Physics and Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/10/2011
Publication Date: 11/30/2012
Citation: Fan, X., Guan, W., Sokorai, K.J. 2012. Quality of fresh-cut iceberg lettuce and spinach irradiated at doses up to 4kGy. Journal of Radiation Physics and Chemistry. 81:1071-1075. Interpretive Summary: Irradiation, a FDA-approved technology, is effective in inactivating foodborne pathogens on fresh fruits and vegetables. However, the tolerance of leafy greens to irradiation has not been fully understood. This study was conducted to evaluate quality changes of fresh-cut Iceberg lettuce and spinach as a result of irradiation at different doses. Our results showed that irradiation at doses of 1 and 2 kilogray is feasible to enhance microbial safety of fresh-cut lettuce and spinach with minimal effect on product quality and consumer acceptance. The information will help produce industry to adopt the technology to decontaminate fresh lettuce and spinach.
Technical Abstract: This study was conducted to investigate radiation tolerance of fresh-cut Iceberg lettuce and spinach. Fresh-cut Iceberg lettuce packaged in modified atmosphere packages and spinach in perforated film bags were irradiated with gamma rays at doses of 0, 1, 2, 3, and 4 kGy. After irradiation, the samples were stored for 14 days at 4 C. Analysis of headspace composition in the packages of fresh-cut Iceberg lettuce indicated that oxygen levels decreased and carbon dioxide levels increased with increasing radiation dose, suggesting that irradiation increased respiration rates of lettuce. Tissue browning of irradiated cut lettuce was less severe than that of non-irradiated, probably due to the low oxygen levels in the packages. However, samples irradiated at 3 and 4 kGy had lower maximum force (texture) and more severe sogginess than the non-irradiated control. In addition, ascorbic acid content of irradiated lettuce was lower than the non-irradiated samples after 14 days of storage, representing 22-40% loss compared to non-irradiated control. The visual appearance of spinach was not affected by irradiation even at a dose of 4 kGy. Consumer acceptance suggested that more people would dislike and would not buy spinach that was treated at 3 and 4 kGy as compared to the non-irradiated sample. Overall, irradiation at doses of 1 and 2 kGy may be employed to enhance microbial safety of fresh-cut Iceberg lettuce and spinach while maintaining quality.