30B-16 |
The effect of low dose gamma irradiation on pectic substances and texture of diced bell peppers and tomatoes |
S. DE COSTA, A. Prakash, and C. Munimbazi. Department of Food Science and Nutrition, Chapman University, One University Drive, Orange, CA 92866 Although low dose gamma irradiation has been shown to be effective in extending the microbiological shelf life of minimally processed produce, one disadvantage is that irradiation can cause softening of plant tissue. Changes in pectic substances have been suggested as a cause of tissue softening. The objective of this study was to determine the changes in pectic substances in diced tomatoes and diced green peppers due to low dose gamma irradiation. Diced bell peppers and diced tomatoes (3/8°¨) were subjected to gamma irradiation using cobalt 60 with doses up to 3.7 kGy and stored for 12 days at 4„aC. Alcohol insoluble solids extracted from the vegetable tissue were analyzed for water soluble pectin, oxalate soluble pectin, and total pectin. Changes in pectic substances were correlated with texture measured by Kramer Shear. Two-way analysis of variance with replication was used to determine effects of irradiation dose and storage time in a randomized complete block design. In tomatoes, irradiation at 3.7 kGy decreased firmness by 50% however the firmness did not decrease further during the 12-day storage. With 1.24 kGy treatment, peak force declined by 39%. A 56% decrease in firmness was also observed in green peppers treated with 3.7 kGy, and a 26% decrease in samples treated with 1.24 kGy. Both vegetables showed significant (p„T0.05) inverse correlation between peak force and water-soluble pectin (WSP). The total pectin content of tomatoes and bell peppers remained relatively constant with irradiation. Irradiation appeared to decrease oxalate soluble pectin (OSP) in bell peppers while the OSP content of tomatoes was not affected. The changes in WSP during irradiation and storage play an important role in tissue softening of diced tomatoes and diced bell peppers. The extent of softening is affected by irradiation dose, storage temperature and the physiological state of the vegetables.
Session 30B, Fruit & Vegetable Products: Sensory, Product Development, Fresh-Cut, and Storage
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