Improvement of non-fat yogurt gel syneresis by heat-unfolded whey protein isolate/mogrosides complexes: Effect on the structural characterization through simultaneous rheological and FTIR techniques

The investigation explores the structural changes and gel properties of heat-unfolded whey protein isolate (PWPI) with mogrosides (MFE) through the simultaneous rheological and fourier transform infrared (FTIR) techniques. The PWPI/MFE complexes potential application in non-fat yogurt were also detected. The results showed that MFE significantly increased the average particle size of the PWPI/MFE complexes and decrease the absolute zeta potential (P < 0.05). Complex formation was evidenced by protein structural changes when PWPI was bound to MFE. Multi-spectral analysis indicated that different MFE concentrations caused protein unfolding and the increase of a disordered structure. The simultaneous rheological and FTIR techniques indicated that the gel properties of PWPI/MFE complexes were much higher than that of PWPI. After addition of MFE, the bands at 2961, 1525, 1351, 1392, 1236 cm−1 occurred simultaneously. The microstructure of the PWPI added with 5 mg/mL MFE exhibited a higher degree of interconnectivity and a denser network than that of PWPI. In addition, the addition of 60 mL 10% PWPI/MFE complexes could significantly improve the syneresis, rheological properties and microstructure of non-fat yogurt. This study provides a theoretical basis for applying PWPI/MFE complexes as a food additive in developing the non-fat dairy foods.