Effect of soymilk substitution on physicochemical properties and sensory preference of instant nasi lemak

Abstract

Coconut milk contains high content of saturated fat and soy milk substitution in food brings new trend of healthy lifestyle. Meanwhile, instant nasi lemak provided convenient version of nasi /emak. Five formulations of instant nasi /emak were prepared with the ratio between coconut milk and soy milk ranged from 100:0, 75:25, 50:50, 25:75, and 0: 100. Substitution of soy milk in instant nasi /emak caused the changes of physical, chemical characteristics and sensory preference of nasi lemak. Physical properties examined including colour, density, water activity, microstructure, rehydration ratio, volume increase and texture analysis; while chemical tests included proximate composition, fatty acid profile and calorie content as well as sensory preference test of instant nasi lemak. This study shows soy milk substitution in instant nasi lemak give better characteristics. Soy milk incorporated in instant nasi lemak caused significant increased (p<0.05) in hardness, springiness, gumminess, cohesiveness, resilience, greenness, yellowness and density. However, this substitution resulted in significant decrease (p<0.05) in adhesiveness, lightness, whiteness, water activity, pores size, rehydration ratio and volume increase of instant nasi lemak. For chemical characteristics, increasing level of soy milk substitution had significantly increased (p<0.05) protein content, fiber content, ash content and carbohydrate content while decreasing fat content and calorie content of instant nasi lemak. In addition, increased soy milk substitution had decreased the percentage of saturated fatty acid and increased unsaturated fatty acid percentage in instant nasi lemak However, it did not significantly affected (p>0.05) moisture content and greenness of instant nasi /emak, as well as springiness, lightness and whiteness of rehydrated nasi lemak The highest scores of sensory preferences for both fresh and rehydrated nasi /emak were attained by samples produced with the ratio of coconut milk to soy milk of 75:25. This sample had higher sensory preference, higher protein content, lower fat content, higher unsaturated fatty acid percentage, and lower calorie content compared to control sample. This study shows that soy milk has potentials to be incorporated in instant nasi lemak with satisfying sensory preference.