Effect of pasteurization and fat, protein, casein to serum protein ratio, and milk temperature on milk beverage color and viscosity

摘要

Our goal was to determine the effect of pasteurization-homogenization, fat and protein concentration,proportion of milk protein that is casein and serumprotein, and temperature on sensory and instrumentalmeasures of viscosity and color of milk-based beverages.A second goal was to use instrumental measuresof whiteness and yellowness to predict sensory measuresof whiteness and yellowness. A complete balanced3 factor (fat, true protein, and casein as a percentageof true protein) design was applied with 3 levels of fat(0.2, 1.0 and 2.0%), 4 levels of true protein (3.00, 3.67,4.34, and 5.00%) within each fat level, and 5 levels ofcasein as a percentage of true protein (CN%TP; 5, 25,50, 75, and 80%) within each protein level for beverageformulation. Instrumental color and viscosity, andvisual sensory color analyses were done on each beverageformulation. For unpasteurized beverages across 3fat levels (0.2, 1, and 2%), changes in CN%TP hadthe largest effect on L values, sensory whiteness, opacity,color intensity, and yellowness, whereas changes infat concentration had a stronger influence on a and b*values. Increasing CN%TP from 5 to 80% increased Lvalues, sensory whiteness, and opacity, and decreasedsensory color intensity and yellowness. The a and b*values increased with increasing fat concentration. Forunpasteurized milk protein beverages within each fatlevel, variation in CN%TP dominated the changes in Lvalues, sensory whiteness, and opacity, and decreased aand b* values, sensory color intensity, and yellowness.The effect of heat (pasteurization and homogenization)and its interaction terms had the second largesteffect on color of milk protein beverages with respectto instrumental color data and sensory appearance attributes.Heat increased L values, sensory whiteness,and opacity, and decreased a and b* values, sensorycolor intensity, and yellowness. Increases in temperaturedecreased instrumental viscosity and changes inprotein concentration and CN%TP had a greater effecton instrument viscosity data within each temperature(4, 20, and 50°C) than fat. Sensory perception of yellownesswas not highly correlated with b* values. Multiplelinear regressions of L, a, and b* values producedmore robust predictions for both sensory whitenessand yellowness than simple linear regression with Land b* values alone, and may be a useful instrumentalapproach for quality control of sensory whiteness andyellowness of milk protein beverages.