Effect of different processes on composition, properties and in vitro starch digestibility of grass pea flour

The objective of this study was to determine the effect of processes of seed disintegration and cooking and their order on digestibility of starch of grass pea seeds. Analyses were carried out in flour made of cooked grass pea seeds (CSF) and in flour made of raw ground seeds and subjected to identical treatments (CF). In addition, physicochemical properties of flour were determined to identify factors which affected starch digestibility. In CSF, analyses demonstrated decreased temperatures and enthalpy of transition and an increased range of transition temperatures. However, enthalpy value was still relatively high, probably as a result of starch retrogradation during drying. Compared to CF, the rate of starch hydrolysis in CSF was significantly lower and, as a consequence, the predicted glycemic index (pGI) was also significantly lower. The rate of CF starch hydrolysis and a high value of its pGI point to a highly significant effect of seeds disintegration before cooking, which resulted in complete gelatinization of starch during cooking. In contrast, incomplete gelatinization of starch during cooking and retrogradation of gelatinized starch during drying were observed in CSF. These changes caused slower starch hydrolysis, lower pGI, and significantly higher content of resistant starch in these flours compared to CF. Results obtained in study demonstrate that flour from cooked grass pea seeds may be used in food products to decrease their GI and to enrich them in resistant starch.