Application of ultrasound treatments to enhance the suspension stability of cloudy phalsa (Grewia asiatica) juice

Natural drinks prepared from fresh fruits and vegetables are nutritious with minimum health risks. The raw juices obtained from fruits have certain quality and sensory issues, including large particle sizes, poor suspension stability, and cloudiness, which result in low consumer attraction. Thus, the efficient processing of natural juices to manage these issues is the current focus of food processors. Conventional techniques employed to resolve these issues have bad impacts on the nutritional profile of natural drinks. Ultrasound is one of the efficient non-thermal processing techniques that causes minimum damage to the nutrients present in juices and has beneficial effects against these issues. In this research, phalsa juice was prepared by blending fresh phalsa fruit with clean water and subjected to ultrasound treatments at different power levels of 510, 850, and 1070 watts at 40, 50, and 60 °C temperatures. The effects of ultrasound treatments on particle size, suspension stability, and microbial populations of the prepared juice samples were examined. The optimized conditions for ultrasound treatment were at 50 °C with 1070 W power for 10 minutes. At optimized conditions, the juice showed enhanced suspension stability, a decrease in mean particle diameters (from 216.92 ± 2.76 μm to 106.26 ± 1.98 μm), cloudiness (less absorbance was measured in the UV-visible spectrophotometer, showing a 660 nm reduction from 0.43 to 0.18 ), and microbial load (from 3.75 ± 0.03 to 2.07 ± 0.37 log CFU/ml).