Comparison of dry- and wet-heat induced changes in physicochemical properties of whey protein in absence or presence of inulin.

Changes in whey protein (10%, w/v) induced by dry-heating (60 °C for 5 days at a relative humidity of 63%), wet-heating (85 °C for 30 min) or the two-combined heating in absence or presence of inulin (8%, w/v) were studied. Mixture of whey protein and inulin showed significantly higher absorbance at 290 nm than whey protein alone in all heating conditions while only dry-heated samples showed significantly increased absorbance value at 420 nm (p < 0.05). Whey protein after heating showed significantly lower zeta potential and inulin decreased the value of all heated samples further (p < 0.05) except for samples after dry-heating. Heating decreased the free sulfhydryl group content of whey protein samples while presence of inulin decreased further (p < 0.05). Dry-heating decreased while wet-heating increased the surface hydrophobicity of whey protein. Inulin had no effect on the surface hydrophobicity of heated whey protein under dry-heating but decreased under wet-heating.