Mechanism of improving solubility and emulsifying properties of wheat gluten protein by pH cycling treatment and its application in powder oils

Wheat gluten protein (WG) is a kind of plant protein with high quality, low price and rich nutrition. But its low solubility limits its application in food products. Therefore, this work modified WG by pH cycling combined with heat treatment, to enhance its solubility and processing properties. Under the condition of pH cycling combined with heat treatment at 80 °C, the solubility of WG increased from 6.7% to 71.1%; the free sulfhydryl group and surface hydrophobicity were significantly improved (from 2.45 μmol/g and 340.86 to 15.27 μmol/g and 2080.73 respectively). The results of SDS-PAGE and the particle size showed that the WG molecules became smaller. The proteomic method was used and there were 3 subunits (A0A3B6LVB5, A0A3B5XV32 and A0A0A7AA82) observed having an impact on the improvement of solubility. Besides, the emulsifying activity index and emulsifying stability index of modified WG have been improved 8 times and 1.6 times, respectively. Furthermore, the powder oils made of the modified WG exhibited enhanced emulsifying and rehydrating characteristics than those of powder oils made of sodium caseinate and soybean protein isolates. Therefore, this work provided a feasible way to enhance solubility and processing properties of WG, by which the modified WG has a good application prospect in powder oils and other products.