Influence of Degree of Hydrolysis on the Functional Properties of Cowpea Protein Hydrolysates

Abstract

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 Applications Cowpea 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 oil-holding 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.