Nutritional, functional, and rheological characterization of black bean (Phaseolus vulgaris) protein concentrate produced by ethanol-assisted precipitation [pdf]

Background.Black bean (Phaseolus vulgaris) proteins represent a promising plant-based alternative to animal proteins, yet their functionality depends strongly on extraction methods.This study evaluates the nutritional, functional, and rheological properties of black bean protein concentrate (BBPC) produced via ethanol-assisted isoelectric precipitation, a mild modification approach that has received limited prior investigation.Materials and methods.BBPC was produced from defatted black bean flour using alkaline extraction followed by ethanol-assisted precipitation at pH 4.0.The concentrate was characterized for proximate composition, amino acid profile, and molecular weight distribution using SDS-PAGE.Functional properties, including solubility, water and fat absorption, foaming, and emulsifying behavior, were evaluated across pH 2-10.Rheological behavior and gelation were examined at protein concentrations of 70-130 g•L -1 and temperatures of 10-60°C using the Herschel-Bulkley model.Results.BBPC contained 64.4% protein and was rich in lysine (4.34 g per 100 g protein) but limited in sulfur-containing amino acids (chemical score = 0.59).The molecular weights of protein fractions ranged from 11.4 to 77 kDa.Solubility, foaming, and emulsifying properties displayed strong pH dependence, with maxima at alkaline pH (10.0) and minima near the isoelectric point.BBPC exhibited high water absorption (3.35 g•g -1 ) and moderate fat absorption (1.01 mL•g -1 ).A structured, shear-thinning, and thixotropic gel formed at a relatively low critical protein concentration (~110-120 g•L -1 ), showing a yield stress of 14.94 Pa at 10°C.Conclusion.Ethanol-assisted BBPC is a functionally effective plant protein ingredient with strong pH-responsive interfacial properties and high gelling ability.While nutritionally incomplete when used alone, its high lysine content and advantageous texturizing, emulsifying, and stabilizing properties support its targeted use in cereal-fortified foods, sauces, and plant-based meat and dairy analogues.