In vivo screening for low glycemic index (GI) rice varieties in Bangladesh and evaluate the effect of differently processed rice and rice products on GI

In quest of screening for low glycemic index (GI) rice varieties in Bangladesh and evaluate the effect of differently processed rice and rice products on GI, a total of 72 Bangladesh Rice Research Institute (BRRI) released high yielding varieties (HYV) were subjected to estimate the glycemic index (GI), in an in-vivo experimental rat model using glucose as standard (control). Our data revealed that BR16, BRRI dhan46 and BRRI dhan69 are categorized as low GI rice varieties in addition to 50 varieties are intermediate GI and 19 varieties are high GI in vivo experimental rat model. In order to assess the effect of differently processed rice such as un-parboiled, parboiled, pressure parboiled, double parboiled milled rice and brown rice on glycemic response in an in vivo experimental rat model, we had selected three rice varieties from three scales of GI group namely BR16 (Low GI), BRRI dhan29 (Intermediate GI) and BRRI dhan28 (High GI). We found that GI value reduces at parboiled mill rice than unparboiled one. It further reduces towards pressure parboiled mill rice, double parboiled milled rice and the most reduced at the brown rice condition. Due to fiber content brown rice showed the lowest GI among all rice processing methods. High GI value grouped BRRI dhan28 rice (GI 70.96 at unparboiled milled rice condition) become intermediate GI grouped rice (GI 65.01 at parboiled mill rice condition) due to temperature effect (forming a kind of resistant starch). In addition our research also reveals that GI of rice based products i.e. flattened, popped and puffed rice are higher GI than rice itself. We concluded that thermal and pressuring process lowering GI value than original because of possible retrogradative changes in starch composition. Rice based rice products might possess higher GI than rice itself because of possibly lesser amount of solid matters.