Protein structural changes in lentil flour during soaking/germination and thermal treatments: Indication of nutritional and functional properties

Functional characteristics of lentil's protein have a significant impact on texture of developed food products and are an important consideration for ingredient manufacturers in food industries. Soaking/germination and thermal treatments are well-known methods in modifying these characteristics by altering protein structure. Therefore, in this study, the combination of these methods at two heat intensity categories, above and below protein denaturation, was utilized to examine modification of the structural, nutritional, and functional properties of processed lentil flours. The results showed that processing of lentil seeds impacted their protein secondary structure from ordered to disordered structures, by decreasing β-sheet and α-helix and increasing intermolecular β aggregates and random coil conformation. In terms of nutritional value, the applied processing improved lentil flours by higher protein content after germination and enhanced protein digestibility after thermal processing. Generally, protein solubility was negatively affected by thermal conditions, with microwave-infrared drying having the most significant impact on reducing protein solubility. Mostly, the processing did not noticeably affect the emulsifying activity and oil binding capacity, while it significantly reduced emulsifying stability at high-temperature methods. The findings suggests that germination-thermal processing combination enhances nutritional/functional properties of lentil flours and provides opportunities for their incorporation into value-added food product formulations.