Effect of cabinet-drying (CD), vacuum-drying (VD) and freeze-drying (FD) methods on the surface hydrophobicity (H0), secondary structure, emulsifying and foaming properties of protein concentrates prepared from different cultivars of cowpea and Bambara bean was investigated.The VD method reduced H0, while freeze-dried concentrates presented high H0. The concentrates prepared by FD presented more β-sheet (40-43%) and less β-turn (19-24%) structures. Bambara bean protein concentrates prepared by FD presented higher emulsifying activity (56-59%) compared to those by VD and CD, while emulsifying activity varied significantly among cultivars of cowpea (46-61%). Protein concentrates prepared by CD showed the highest foaming ability.

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The effect of different drying methods used in the preparation of protein concentrates from different cultivars of cowpea and bambara bean was investigated. Protein was extracted by the isoelectric precipitation method and subsequently dried by cabinet drying (CD), vacuum drying (VD) and freeze drying (FD). The protein extraction yield and protein content were high. The subunit composition of protein concentrates was characterized by electrophoresis. The drying methods affected water-holding capacity, oil absorption capacity and solubility of protein concentrates depending on cultivars. Water-holding capacity was adequate for its utilization in viscous foods. The protein concentrates prepared by FD showed higher oil absorption capacity than those by CD and VD. The protein concentrates prepared by FD showed lower solubility at pH 2-6, and above pH 6 the concentrates prepared by VD presented higher solubility compared with those by CD and FD. This study provided useful information to optimize utilization of legume protein concentrates in the food industry. PRACTICAL APPLICATIONSCowpea and bambara bean cultivars could be used in the preparation of protein concentrates due to their good nutritional quality and low cost. Techniques used during the preparation of protein concentrates usually involve the conversion into a dry powder form that facilitates stable and long-term storage, enabling their use as ingredient in food applications. In this regard, the effect of cabinet drying, vacuum drying and freeze drying in the functional properties of cowpea and bambara bean protein concentrates was investigated. The freeze-drying technique was adequate for utilization of concentrates in viscous foods, bakery products and in the cold meat industry as these concentrates presented high water-holding and oil absorption capacities. The vacuum-drying technique produced concentrates with high solubility at pH 2 and above pH 6, and was adequate for concentrates that could find utilization in the fortification of beverages. Choosing appropriate drying technique and cultivar could determine utilization of protein concentrates in the food industry.

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The solubility of cowpea protein hydrolysate was adequately optimized by response surface methodology, and the hydrolysate showed adequate functionality for use in food. © 2016 Society of Chemical Industry.

Effect of physicochemical properties and secondary structure conformation, on the functional properties of protein concentrates prepared from grain legumes was investigated using response surface methodology. Appropriate models were built on the basis of the best subset technique. Oil‐holding capacity was mainly influenced by the secondary structure of proteins, particularly unordered structure, β‐sheet, and β‐turn. Protein solubility depended on secondary structure and surface hydrophobicity of proteins, and solubility decreased with increasing hydrophobicity. Interaction between solubility and hydrophobicity was significant for emulsifying activity, and EA increased with increasing solubility and hydrophobicity. High emulsion stability of legume proteins necessitated high β‐turn secondary structure proportion, solubility, and hydrophobicity. Protein unfolding, particularly high unordered, and β‐turn structures and high solubility were required for high foaming ability of legume proteins. In summary, the importance of this study was to increase the utilization of grain legume proteins in the food and non‐food industry. Practical applications It is important during food processing or when using an underutilized grain legume protein source as ingredient or supplement in the formulation of food products, to predict the functional properties of the protein. Functional properties are important for the consumer acceptance of food product. The physicochemical properties of protein such as surface hydrophobicity and secondary structure could be used as a basis to predict functionality. In this connection, this study provided effects of the variation of physicochemical properties and secondary structure of grain legume proteins on oil‐holding capacity, solubility, emulsifying and foaming properties. The aim of this study was to enhance the utilization of grain legume proteins as nutritional and functional ingredient.