Application of Barley- and Lentil-Protein Concentrates in the Production of Protein-Enriched Doughnuts

Barley and lentil proteins have good emulsifying and foaming capacity, which make them suitable ingredients in many food formulations. The aim of this research was to develop protein-enhanced foods based on barley and lentil proteins using doughnut as a food model. In enriched doughnut formulations, barley proteins were used to substitute for 20% of the wheat flour (doughnuts labeled as barley doughnut, barley/lentil doughnut [BLD], and vegan doughnut [VD]) and lentil proteins were used as an egg replacer (in BLD and VD doughnuts). A VD formulated with barley and lentil proteins to replace egg white protein and milk was also tested. The physicochemical parameters, proximate composition, and sensory qualities of the prepared doughnuts were studied and compared with the control doughnut (CD) containing egg white and milk. The protein-enriched doughnuts showed better cooking characteristics with reduced cooking loss and diameter reduction compared to the control. In addition, they had a higher protein and -glucan content. During the storage-stability test, the doughnuts containing lentil and barley proteins showed higher values for hardness, chewiness, and gumminess compared to the control. However, the sensory scores for appearance, flavor, and overall liking were rated more favorable toward the CD. It is also noticed that the fat content and caloric values increased for some protein-enriched doughnut formulations. Considering the consumers' demand of high-protein convenient snack foods, the doughnuts prepared with barley and lentil proteins may have potential for commercialization with some improvements.