EFFECTS OF PRETREATMENT WITH GAMMA-RAYS OR MICROWAVES ON STORAGE STABILITY OF DRY BEANS

The objective of this work was to study the effects of gamma radiation or microwave treatment on physical, chemical, and sensorial properties of dry beans during storage. Microwave treatment for 2 min or gamma irradiation at 2 kGy was applied. Samples were stored at 4-5-degrees-C in a refrigerator and at 30-degrees-C, 75% relative humidity (RH), for 6 months. The hydration capacity of samples stored at 4-5-degrees-C for 6 months was about 60 % that of samples stored at 30-degrees-C, 75% RH. Gamma radiation increased the hydration rate and decreased cooking time and hardness of the seeds, whereas microwave treatment resulted in increased hardness and cooking time. Sensorial attributes were preserved in all samples kept under refrigeration (4-5-degrees-C) but deteriorated considerably at 30-degrees-C, 75% RH. Overall, the sensory properties of the irradiated samples did not differ (p less-than-or-equal-to 0.05) from those of the controls, while the microwave-treated samples presented inferior sensorial properties. Storage for 6 months at 30-degrees-C, 75% RH, reduced phytate to 50% of the original values in the control and irradiated samples and to 60% in the microwave-treated sample. For the same storage condition and time, methionine was reduced to 72,75, and 63% of original value, in the control, irradiated, and microwave-treated samples, respectively.