30G-34 |
Combination of ionizing radiation and heat shock on quality of fresh-cut iceberg lettuce |
X. FAN1, P. M. Toivonen2, and K. B. Sokorai1. (1) USDA-ARS-Eastern Regional Research Center, 600 E. Mermaid Ln., Wyndmoor, PA 19038-8598, (2) Pacific Agri-Food Research Centre, Agriculture & Agri-Food Canada, Summerland, BC V0H 1Z0, Canada Ionizing radiation can effectively inactivate foodborne pathogens in many fresh fruits and vegetables. However, irradiation at high doses may induce undesirable quality changes. Therefore irradiation will likely be used in combination with other treatments to achieve the 5-log reduction of pathogens on fresh and processed fruits and vegetables. This study was conducted to investigate the effect of heat shock in combination with irradiation on the quality of fresh-cut lettuce. Fresh-cut iceberg lettuce, immersed into 5 C or 47 C water for 2 min and packaged in breathable film bags (oxygen transmission rate 4,000 cc/h/m2 at 73 C), was irradiated at 0, 0.5, 1 and 2 kGy. The lettuce was then stored at 3C for 21 days. Irradiation or warm water dipping did not consistently affect color measured by a Hunter color meter, but visual observations revealed that warm water dipping or irradiation at 1 and 2 kGy decreased browning of lettuce. Cold water-dipped lettuce exposed to 2 kGy radiation had lower shear force at day 7 and 21. Antioxidant activity was increased by irradiation in the cold water-dipped lettuce at the early period of storage (day 1 and 7) but the effect disappeared in the latter period of storage (day 14 and 21). Phenolic content was enhanced by irradiation only in cold water-dipped lettuce. Vitamin C (ascorbic acid plus dehydroascorbic acid) content was not affected by irradiation. At a dose of 2 kGy, irradiation caused damage on cell membrane evidenced by the soggy appearance as well as by the increase in electrolyte leakage measured with a conductivity meter. Overall, our results suggest that heat shock treatment in combination with low dose (0.5 and 1kGy) radiation can be used to enhance food safety and quality of fresh-cut lettuce.
Session 30G, Fruit & Vegetable Product: Processed Fruits and Vegetables
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