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.

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The effects of limited enzymatic hydrolysis with pepsin on the functional properties and molecular characteristics of cowpea protein concentrate (CPC) were investigated. Hydrolysates were prepared at degrees of hydrolysis (DH) 5-30%. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis demonstrated that globulin was the major protein component of CPC, and enzymatic breakdown of polypeptides was selective. As a result, significant changes in the functional properties of hydrolysates were noticed as compared to the protein concentrate. Then, cowpea protein hydrolysates (CPHs) showed good water solubility index at pH 7 (>95%) and pH 4.5 (>55%), at DH 20 and 30%, respectively. Oil-holding capacity, emulsifying activity and foaming capacity were also improved by the enzymatic hydrolysis, while proteolysis was detrimental to foam stability and did not improve emulsion stability at DH 10-30%. Therefore, CPHs showed good potential for utilization in food formulations. PRACTICAL APPLICATIONSCowpea is a good nutritional value and available protein source, which could be used for a large-scale production of protein hydrolysates. Enzymatic hydrolysis of food proteins is mostly used to produce ingredients or supplements in food and beverages. In this regard, functional properties of protein hydrolysates are largely dependent on the degree of hydrolysis (DH), which needs to be controlled to avoid excessive proteolysis that can impair functionality and cause unfavorable effects. Then, functional properties of cowpea protein concentrate hydrolyzed by pepsin at DH 5-30% were investigated. The results showed that solubility and oilholding capacity were higher at DH 20-30%. Emulsifying activity and foaming capacity were also improved following hydrolysis, while de-decreasing molecular weight of protein was detrimental to foam stability of hydrolysates. In summary, cowpea protein hydrolysates showed adequate functional properties for utilization as food ingredient and the peptides produced could turn out to present some biological activities.