Effect of biopolymer mixing ratios and aqueous phase conditions on the interfacial and emulsifying properties of lentil protein isolate–κ‐carrageenan and lentil protein isolate–ι‐carrageenan complexes

Abstract

AbstractBackground and objectivesThe use of plant protein ingredients within the food industry is increasing rapidly due to their lower cost, greater environmental sustainability, perceived safety concerns related to consuming animal products, and consumer dietary preferences. Lentil protein, as an emerging nonsoy, gluten‐free, plant‐based protein, could play more important role in food processing. However, plant proteins generally contribute lower solubility than animal proteins; incorporation of polysaccharides such as carrageenan could tailor the functionality of lentil protein. This work aimed to investigate the complexation behavior between lentil protein isolate (LPI) and carrageenan (κ‐carrageenan: κ‐C and ι‐carrageenan: ι‐C) as a function of pH and biopolymer mixing ratio, and the emulsifying properties of their resulting soluble and insoluble complexes.FindingsIncorporation of both κ‐C and ι‐C into the LPI solution led to the suppression of large protein aggregates being formed during a turbidimetric pH acid titration. As LPI–carrageenan mixing ratio decreased, maximum optical density (max OD) values for both LPI‐κ‐C and LPI‐ι‐C systems decreased. Emulsions made at pH 6 showed higher emulsion stability than those made at pH 3.5 for each sample. Emulsions at pH 6 also formed smaller, more uniform, and higher charged droplets and showed lower interfacial tension. 4:1 LPI‐κ‐C and 4:1 LPI‐ι‐C emulsions at pH 6 showed higher emulsion viscosity and higher corresponding continuous phase viscosity.ConclusionsSoluble and insoluble complexes were formed between LPI and both carrageenan polysaccharides through electrostatic interactions at pH 6 and pH 3.5, respectively. Emulsions prepared at pH 6 showed higher stability than emulsions at pH 3.5, where the highest emulsion stability was contributed to 4:1 LPI‐κ‐C and 4:1 LPI‐ι‐C emulsions.Significance and noveltyLentil protein interacted with carrageenan through electrostatic attraction, where soluble complexes were formed between the positive patches on LPI and negatively charged carrageenan and insoluble complexes were formed between positively charged LPI and negatively charged carrageenan. Both types of electrostatic complexes were used to prepare emulsions, and soluble complexes were shown to contribute better emulsion stability than insoluble complexes. Preparation of the stable LPI–carrageenan‐based emulsion is a low‐cost, nonsolvent, and relatively easy process, which shows potential for further food applications.