Effect of storage materials and duration on the physicochemical, pasting and microstructural properties of low glycemic index rice flour

Abstract

This study investigated physicochemical, glycemic index, pasting and microstructural properties of low glycemic index rice flour (LGIRF) stored in two different packaging materials (low density polyethylene-LDPE and metalized polyester-Met-PE) under accelerated storage conditions (38 ± 2 °C and 90–92% RH) for three months. The different properties were evaluated after every one month. Protein, fat, fibre and carbohydrate content decreased slightly while, water activity, moisture and ash of both control and LGIRF increased significantly with storage (P < 0.05). Total starch, in vitro glycemic index and glycemic load were higher in control and decreased during storage (P < 0.05). However, resistant starch, total sugars, reducing sugars and degree of sweetness in LGIRF exhibited higher, although non-significant variation relative to control during storage. Pasting properties revealed that peak and breakdown viscosities decreased while final and setback viscosities increased during storage (P < 0.05) however holding viscosity and pasting temperature exhibited non-significant variation (P > 0.05). Further, all pasting properties were significantly higher in control except pasting temperature (P < 0.05). All farinographic properties exhibited non-significant difference during storage and were significantly higher in control. Overall, while comparing LDPE and MeT-PE samples non-significant variation was observed in all properties. Microstructural studies showed that integrity of starch granules in LGIRF samples were least altered during storage.