Optimization of Ultrasonic and High Hydrostatic Pressure Conditions on Quality Parameters of Mulberry (Morus Moraceae) Juice Using Response Surface Methodology

Abstract

The Box-Behnken design response surface method was employed to analyze the synergistic effects of manosonication on some quality parameters of mulberry juice. Activity of polyphenol oxidase (PPO) was significantly affected by the linear terms of ultrasonic frequency and pressure, as well as the interaction between ultrasonic frequency and pressurizing time. Peroxidase (POD) was significantly affected by the interaction between ultrasonic time and pressurizing time as well as the quadratic term of ultrasonic time. Yeast and bacteria were inactivated to levels beyond detection. Model desirability prediction at 95% confidence gave optimal manosonication levels as 25.00kHz, 15.35min, 376.36MPa and 10.01min for ultrasound frequency, ultrasound time, pressure and pressurizing time, respectively. At these optimum levels, the predicted % anthocyanin retained activities of PPO and POD, color brightness, hue angle and chroma were 83.08%, 45.55%, 53.93%, 7.59, 112.09° and 11.74, respectively. The overall desirability index was 0.639. Practical Applications: The independent factor levels used for the manosonication process were adequate to reduce microbial levels to beyond detection, a high percentage of anthocyanin content was retained, residual polyphenol oxidase and peroxidase activities were significantly reduced, while color parameters were minimally affected. Therefore, the optimized manosonication conditions obtained in this work using the response surface methodology provide the industry with the requisite information for adoption and utilization in processing high-quality mulberry juice as well as other fruit juices. Consumers' continuous request for products with extended shelf life, having fresh-like taste, while maintaining their nutrients and essential phytochemicals vital for good health, without the use of antimicrobials or heat, could be achieved by manosonication conditions used in this work.