Optimization of Thermoultrasound Conditions for the Processing of A Prickly Pear Juice Blend (Opuntia Ficus Indica) Using Response Surface Methodology

The aim of this study was to determine the optimal conditions for thermoultrasound treatment of a prickly pear juice blend (two varieties) using response surface methodology. The effect of two independent variables: temperature (40–50C) and time (15–25 min) on the physicochemical, microbiological, and antioxidant properties of the juice blend were evaluated. Temperature and time during processing significantly affected these parameters. The optimum thermoultrasound conditions were temperatures of 44–46C and times of 19–20 min. Under these conditions a reduction >3 log10 CFU/mL was achieved for total plate count, enterobacteria and yeast counts; pectin methyl esterase activity was 54% less than the control, and the content of total phenolic compounds (880 mg GAE/L) and ascorbic acid (230 mg AA/L) contributed to maintain the antioxidant capacity of the juice blend measured by ABTS (350 µmol TE/L), DPPH (1,900 µmol TE/L), and chelating activity (64%). Practical Applications Thermoultrasound is an alternative technology for food preservation that inactivates microorganisms and enzymes in fruit juice without causing unwanted effects associated with conventional heat treatments. The optimized processing conditions reported in this study can be useful for the food industries that want to use thermoultrasound as an alternative to pasteurization for the manufacture of fruit juices.