Effect of Gamma Irradiation on Shelf Life, Nutritional, and Glycemic Properties of Three Indian Brown Rice Varieties

Abstract

Brown rice (whole grain, BR) has lower glycemic index (GI), is a healthy replacement for white rice (WR). However, BR has a short shelf life, is susceptible to pest infestation. Gamma irradiation is a safe approach to prevent the latter. This study examines effect of gamma irradiation on the physical, cooking, nutritional, shelf life and glycemic properties of three Indian parboiled BR. Parboiled BR of ADT-43, BPT-5204, and Swarna rice varieties were packed in polyester and polypropylene pouches (60 µ thickness) and subjected to gamma irradiation [750–820 Gy] (IR). Appropriate controls without irradiation (NIR) were maintained. Irradiation did not induce major changes in the physical and nutritional properties, except for resistant starch which significantly increased after irradiation in ADT-43 and BPT-5204. Irradiation reduced the cooking time, increased loss of solids in the cooking water and decreased apparent water uptake (particularly in BPT-5204). IR varieties exhibited longer shelf life (8–9 months) compared to 6 months shelf life of NIR varieties. The shelf stability of IR Swarna rice was superior in terms of delayed rancidity development compared to all other rice. All BR samples exhibited the ranking of ‘like moderately’ in the sensory acceptability tests at 6 months of storage and scores decreased subsequently. Irradiation did not affect GI [all showed medium GI, except a high GI for IR BPT 5204] and helped in shelf life extension of parboiled BR by preventing insect infestation.