Modulating commercial pea protein gel properties through the addition of phenolic compounds

Abstract

The use of pea protein in dense food is limited because of the low gel strength. Commercial pea proteins were modified with phenolics under alkaline conditions (pH 9, 24 h) that favour covalent bonding. Three phenolic compounds that differ in molecular size but contain similar structural units were selected (gallic acid, 0.17 kDa; epigallocatechin gallate, 0.458 kDa; tannic acid, 1.71 kDa) to better understand the role of molecular weight and added hydroxyl and aromatic groups on the gelling properties. The effect of the dose on gelling properties was studied by varying the phenolic concentrations (0–4 mM). The maximum changes were observed for conjugates prepared with tannic acid: colour, ΔE 38; decreased concentration of binding sites, 43%; solubility, 31%. The maximum increase in gel strength was 16-fold from 3.0 to 48 kPa. The result was positively correlated with the mass concentration of the added phenolic compounds, molecular weight and the approximate number of hydroxyl groups. Modification of pea proteins with phenolics can be as effective as adding thickening agents to increase the gel strength. To increase the elasticity of pea protein gel, the phenolic concentration added should not exceed 1.36 g/L, which is equal to 3.8 wt% of the protein mass. We demonstrated that pea protein modification with phenolics makes a useful tool to tailor gel strength and elasticity based on the molecular weight and the dose of phenolic compounds added.