Limited Proteolysis, Evaluating the Degree of Hydrolysis and Molecular Weight Profile of Protein Hydrolysates from Vigna subterranea and Cajanus cajan

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The protein hydrolysates of two neglected and underutilized legumes; Vigna subterranea (Bambara groundnut) and Cajanus cajan (Pigeon pea) were electrophoretically profiled having previously been subjected to limited proteolysis. The limited enzymatic hydrolyses were carried out with alcalase, pepsin and papain while the Ninhydrin protocol was used to follow the degree of hydrolysis. Response surface D-optimal design was used to plan two set of 17 experimental runs one for Bambara groundnut protein and the other for Pigeon pea protein. The initial design which followed a quadratic model was obtained using the two treatment factors: time of hydrolysis (10.00-120.00 min), numeric factor and type of enzyme (alcalase, pepsin and papain), categoric factor. Bambara groundnut proteins were only marginally vulnerable to hydrolysis just as Pigeon pea proteins were. However, pepsin had the least degree of hydrolysis whereas alcalase which generally has a larger molecular weight had the highest degree of hydrolysis for Pigeon pea protein. Papain’s performance in degree of hydrolysis may be due to the low cysteine amino acids in Pigeon pea. On the other hand, alcalase had the least degree of hydrolysis whereas papain had the highest degree of hydrolysis for Bambara groundnut protein. The image J analysis of the electrophoregram of the hydrolysates at the 10th min and 120th min for Bambara groundnut and Pigeon pea proteins confirmed the actions of these enzymes. It also confirmed the presence of numerous polypeptides of relatively low molecular weights especially at the 120th min. It is believed that the technique of limited proteolysis would be mastered for NULs such as Bambara groundnut and Pigeon pea proteins, and subsequently; their surface functional properties and thus, the food industrial applications of their resultant polypeptides would fully be realized.
A Thesis Submitted To the Department Of Food Science and Technology in Partial Fulfilment of the Requirements for the Award of the Degree Of Master of Science in Food Science and Technology, 2014