Combined effects of ionic strength and enzymatic pre-treatment in thermal gelation of peanut proteins extracts

Abstract : Peanut proteins are mostly composed of arachins and conarachins, globular proteins that can form gels under thermal denaturation or enzymatic treatment. We explore here how ionic strength (0.5 M or 0.8 M) and gelation process (a thermal treatment preceded or not by an enzymatic pre-treatment) affect peanut protein gel properties. Gel formation and final properties are characterized by rheology, and gel structure by confocal microscopy. We show that the ionic strength imposed during protein extraction determines the arachins/conarachins ratio, and that conarachins-rich samples give stronger gels, which is attributed to their higher content in free thiol groups and lysine residues. The gel storage modulus exhibited a power-law dependence with the protein concentration, which exponent depends on the gelation process. Rheological results, together with confocal microscopy imaging, showed that an enzymatic pre-treatment results in denser structures.