Effect of different temperatures and time on the physicochemical properties of tiger nut milk, in terms of pH, viscosity, and color

Abstract

Heat pasteurization is sometimes detrimental to the visual and structural profile of tiger nut milk, which is a popular non-dairy alternative. This study investigates how to optimize temperature and time to provide maximum safety and try to minimize the physicochemical and aesthetic changes in the final beverage product. This study was carried out at Delta State University, Nigeria, to assess the effect of different pasteurization temperature and time on the quality of tiger nut milk. A 3x3 factorial design was used to evaluate the milk sensory, physicochemical, nutritional and microbial properties compared with an unpasteurized milk control sample and a 14 day shelf-life trial. Two-way ANOVA and advanced statistical models validated the data and ten semi-trained panelists carried out the sensory scoring using a nine-point hedonic scale. These results indicate that the pasteurization temperature and processing time have a significant and strong effect on the physicochemical properties of tiger nut milk. With increasingly harsh processing conditions, the milk becomes more acidic as the result of chemical reactions caused by the heat and organic acids being formed. At the same time, a unique thickening effect occurs in the drink, which is reflected by a gradual increase in the viscosity, caused by the gelatinization of starch and denaturation of proteins. Thermal treatment also leads to darkening of the milk, which is indicated by the reduction of lightness values, due to the degradation of the milk pigment, in addition to the Maillard reactions and caramelisation. Both temperature and time are found to have an effect on these changes, but temperature is found to be the more important of the two factors. Overall, the study highlights the significance of optimizing pasteurization conditions to ensure food safety while preserving the visual appeal and texture of tiger nut milk for food processors.