Impact of defatting methods on the physicochemical and functional properties of white lupin protein isolates

Lupin Protein Isolates (L) are considered as promising ingredients. The effects of different solvent extractions of un-defatted (L-U), hot (L-HD) and cold (L-CD) lupin flour on the physicochemical, functional and structural parameters were determined. Hot defatting increased the protein yield and the purity, and increased the particle size, while cold defatting decreased the particle size of lupin isolates. Regarding the amount of free sulfhydryl groups, hot defatting allowed a reduction in free sulfhydryl groups and an increase in the amount of disulfide bridges. Hot and cold defatting resulted in a remarkable decrease in the maximum fluorescence intensity of lupin protein isolates. Regarding the secondary structure determined by mid-infrared, all protein isolates showed similar behavior, although some differences are observed. Hot defatting promoted a significant increase in β-sheet and a decrease in β-turn and aggregates A2 levels. In terms of functionality, L-CD and L-HD behaved fundamentally differently from L-U. Hot defatting leads to protein isolates with improved functional profiles in emulsifying stability index and cold defatting improves significantly solubility, oil adsorption capacity and emulsifying activity index.