Rheological study of starch and dairy ingredient-based food systems

An oscillatory probe rheometer was used to measure the basic rheological properties of food model systems consisting of starch–water, starch–protein, starch–sugar, and starch–sugar–protein mixtures. The mixtures were heated to 85 °C, and the rheological properties of the mixtures were measured during the cooling phase. The independence of complex modulus (G*) on frequency of oscillation indicated that the starch and water system produced stronger gels than systems containing WPI due to its inactive filler. During the cooling, G′ of starch–WPI (1:0.3) gels decreased but started to increase at warm temperature due to the effect of hydrophobic bonds. The addition of sucrose to the starch system lowered G′ at 85 °C. During the cooling, G′ of starch–sucrose gels increased, due to the effect of hydrogen bonds. Replacement of 50% sucrose with lactose caused different cooling processes due to the different sugar. Addition of WPI to the starch and sucrose system decreased G′ at 85 °C. During the cooling, G′ increased due to the effects of hydrophobic and hydrogen bonds. Substitution of 50% WPI with egg white protein did not change this, which might be beneficial in increasing elastic modulus and the rigid structure of bakery products during the later stage of baking and during cooling. In a pancake, addition of whey protein concentrate decreased the G′, probably due to the limit of available water for gelatinization of starch and gelation of proteins.