Enzymatic Hydrolysis of Pulse Proteins as a Tool to Improve Techno-Functional Properties

Abstract

Pulse proteins are being increasingly investigated as nutritious and functional ingredients which could provide alternatives to animal proteins; however, pulse protein ingredients do not always meet the functionality requirements necessary for various applications. Consequently, enzymatic hydrolysis can be employed as a means of improving functional properties such as solubility, emulsifying, foaming, and gelling properties. This review aims to examine the current literature regarding modification of these properties with enzymatic hydrolysis. The effects of enzymatic hydrolysis on the functionality of pulse proteins generally varies considerably based on the enzyme, substrate, processing steps such as heat treatment, degree of hydrolysis, and pH. Differences in protease specificity as well as protein structure allow for a wide variety of peptide mixtures to be generated, with varying hydrophobic and electrostatic properties. Typically, the most significant improvements are seen when the original protein ingredient has poor initial functionality. Solubility is usually improved in the mildly acidic range, which may also correspond with improved foaming and emulsifying properties. More work should be carried out on the potential of enzymatic hydrolysis to modify gelation properties of pulse proteins, as the literature is currently lacking. Overall, careful selection of proteases and control of hydrolysis will be necessary to maximize the potential of enzymatic hydrolysis as a tool to improve pulse protein functionality and broaden the range of potential applications.

Keywords: enzymatic hydrolysis; functional properties; hydrolysate; plant protein; protease; pulse proteins.

Figure 1

Schematic representation of protease sequence specificity. Adapted from Rawlings and Barrett [31], permission obtained.

Figure 2

Generalised pH dependent solubility curves showing a typical solubility profile for non-hydrolysed pulse protein and two potential profiles for solubility after hydrolysis. Black: typical pattern for non-hydrolysed pulse proteins; red: hydrolysate with improved solubility near isoelectric point but otherwise reduced solubility; green: hydrolysate with improved solubility across the pH range.