6533b873fe1ef96bd12d530d

RESEARCH PRODUCT

Study of the interactions and physicochemical properties of pea and egg white protein mixtures : from the colloidal to the gelled state.

subject

description

In recent years, due to the growth of world population, people's consumption of animal protein has increased, leading to the increase of greenhouse gas emissions and land occupation. Therefore, it is necessary to partially replace animal protein with vegetable protein to increase the proportion of vegetable protein in daily consumption and developing mixed food systems seems to be one adequate solution. Pea proteins as a source of plant proteins have good nutritional properties but with limited functional properties while egg white (EW) has good functional properties such as gelling and foaming. Thereby, the physicochemical interactions from mixtures of both types of protein needs to be understood to develop hybrid protein products. In the present work, pea proteins as pea protein isolate (PPI) and EW were prepared at total protein concentration of 10% w/w. The colloidal interactions in solution, thermal and gelation properties of the mixtures were studied as a function of different weight ratios (PPI/EW, 0/100, 25/75, 50/50, 72/25. 100/0) and different pH (7.5 and 9). To understand the interactions in PPI-EW mixtures, PPI in admixture with different EW protein fractions (ovalbumin (OVA), ovotransferrin (OVT), and lysozyme (LYS)) was analyzed by combined methods such as isothermal titration calorimetry (ITC), dynamic light scattering (DLS), laser granulometry, and confocal laser scanning microscopy (CLSM) and optical microscopy. Strong exothermic interactions between PPI and LYS lead to aggregation via electrostatic interactions. No or very weak interactions were detected between OVT or OVA and PPI whatever the pH. Thermal and gelation properties of the mixed systems were characterized through solubility profile with pH, SDS-PAGE, Differential Scanning Calorimetry (DSC), dynamic rheology (25-95-25 °C), texture analyses, CLSM, and the adding of dissociation agents after gelation. Thermal denaturation temperature (Td) and enthalpy were slightly or not influenced depending on the pH. Td of OVT, LYS and legumin changed due to the interactions between proteins. Gel formation was governed by EW proteins and elastic modulus (G’) decreased with EW content in mixtures. Gelation point of OVT (~59 °C) increased around 3 ℃ giving an interesting indication for further pasteurization treatment application. Meanwhile, gels obtained from mixed proteins (containing at least 50% egg white) were constituted of a network of egg white proteins, including aggregates of pea proteins. Strong interactions including disulfide bridges and hydrophobic interactions were at the origin of the structure of the egg white network. Weak interactions including more hydrogen bonds could explain the lower viscoelastic properties of PPI-based gels. In mixed gels, the egg white proteins constitute the basic architecture of the protein network. The gelation of EW is accompanied by the formation of protein aggregates which may be pure PPI aggregates or mixed aggregates consisting of pea globulins and some egg white proteins. Further investigations on protein functionality (foaming) and effect of functionalization treatments such as dry heating of powder are expected.