Modification in starch structure of soaked and germinated lentil seeds under various thermal processing methods, including conventional, microwave, and microwave-assisted techniques

Abstract

Adding lentil flours as an affordable and sustainable plant-based ingredient in food formulation plays vital role in promoting human health and reducing the environmental footprint of human diet. Also, the inclination toward sustainable food products requires the introduction of green technologies as the substitution of conventional heating. A proper substitution demands investigating the impact of different heat transfer mechanisms of conventional and green volumetric heating processes on starch gelatinization and enhancement in starch structural, functional, and nutritional properties. Hence, modified lentil flours through soaking/germination pretreatment followed by volumetric heating (microwave-infrared and vacuum-microwave drying) and conventional heating (roasting and convective air drying) were examined in this study. The results showed that using microwave-infrared not only significantly decreased processing time but also created a similar gelatinization degree compared to the lentils treated by roasting at 240°C. Vacuum-microwave also found a suitable substitution for convective air drying, producing similar modified starch at a shorter processing time. Almost all thermal treatments improved total starch digestibility; however, microwave-infrared drying and roasting increased rapidly digestible starch while vacuum-microwave and convective air drying enhanced slowly digestible starch. Generally, soaking/germination followed by the mentioned dryings leads to modified flours by changes in their starch structure, resulting in the effective utilization of pulse flours as a promoting food ingredient.