ARS | Publication request: Effects of gamma irradiation, modified atmosphere packaging and delay of irradiation on quality of fresh-cut iceberg letuce

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 14, 2010
Publication Date: February 1, 2011
Citation: Fan, X., Sokorai, K.J. 2011. Effects of gamma irradiation, modified atmosphere packaging and delay of irradiation on quality of fresh-cut iceberg letuce. HortScience. 46:273-277.

Interpretive Summary: Recent outbreaks of foodborne illness associated with leafy greens highlighted the limitation of chemical sanitizers that are currently used by the produce industry. Ionizing radiation is known to effectively eliminate human pathogens such as Escherichia coli O157:H7 on fresh produce. However, the commercial application of irradiation to fresh produce is still limited partially due to concerns about possible damage to product quality. This study was conducted to investigate quality of irradiated cut lettuce (salads) during storage at 4 C. Our results demonstrate that appearance and texture of cut lettuce were not negatively affected by low dose irradiation providing the salads were stored in modified atmosphere packages. The information is useful for produce industry to implement this FDA-approved technology to enhance microbial safety of Iceberg lettuce.

Technical Abstract: The study was conducted to investigate the effect of modified atmosphere packaging (MAP) and delay of irradiation application on the quality of cut Iceberg lettuce. Overall visual quality and tissue browning of cut lettuce were evaluated using a scale of 9-1 while texture was analyzed instrumentally during 14 days of storage at 4C. Results showed that irradiation (0.5 and 1.0 kGy) of cut lettuce induced tissue browning when stored in air; however, when cut-lettuce was stored in MAP, irradiated lettuce had better appearance than the non-irradiated ones due to lower O2 levels in the packages of irradiated samples compared to the levels in control packages. In general, irradiation at doses of 0.5 and 1.0 kGy did not affect firmness of the lettuce. After 14 days of MAP storage, overall visual quality of non-irradiated samples had a score around 4, a score below the limit of sales appeal, while the two irradiated samples had scores of 6.5-7.9, indicating the irradiated samples had a fair to good quality. Delaying irradiation by one day after preparation of cut lettuce did not significantly (P>0.05) affect cut edge browning, surface browning, or overall visual quality compared to lettuce irradiated immediately after preparation. Our results suggest that MAP is essential to minimize quality deterioration caused by irradiation.