PhD cadidate, Queensland University of Technology
Buffalo milk is the world second highest producing milk type and the yogurt produced from buffalo milk is considered a delicacy in some parts of the world. Typically buffalo yogurt shows poor gel strength and excessive whey (serum) separation due to there large milk fat globules and porous gel structure. This is one of the major difficulty faced by manufacturers during the production and transportation. Ultrasound is a good alternative to minimize the above defects inherited to buffalo milk. Power ultrasound may modify the functional properties of buffalo milk fat globules which collectively improve the gel firmness, stability and reduce whey separation in buffalo yogurt. In order to get the desired effect, the optimum level of frequency and amplitude of ultrasound should be carefully selected. However, there is a knowledge gap on the ideal ultrasonic process parameters which can be used for the emulsification of buffalo milk fat. As well, it was reported that upon the exposure to ultrasound, the functional properties of milk fat globules is being changed. Nevertheless, it is not clear how ultrasound induced functional fat globules/milk protein complexes modifies the gelation kinetics of buffalo milk gels. Hence, as the initial step, a study was conducted to evaluate the effects of ultrasonic homogenization on droplet diameter and size distribution of buffalo milk fat emulsion. A probe-type ultrasonic processor was used for the experiment. During sonication, milk samples were immersed in an ice bath in order to control the temperature rise. Milk samples were sonicated under different amplitudes for different time periods. Mean droplet diameter and size distribution of MFG were analyzed using Malvern Mastersizer 2000. Optical microscopy was used to observe the structural changes to the MFG emulsion during storage. It was observed that ultrasound treatment alter the stability, firmness and some other functional properties of buffalo yogurt in a desirable way under predetermined amplitude and frequency. Therefore, it can be concluded that use of ultrasound technique is a good alternative to minimize most of the defects associated with buffalo yoghurt oruduction in the industry.