Thermosonication parameter effects on physicochemical changes, microbial and enzymatic inactivation of fruit smoothie.

Abstract

With the aim of developing a fruit-based beverage in products which are severely damaged by heat, a high-intensity ultrasound treatment combined with moderate heat treatment (called thermosonication) was applied. A fruit smoothie (mango, jackfruit and rice milk) was thermosonicated applying a Box-Benhken model with amplitude (70, 77.5 or 85%), time (15, 20 or 25min) and temperature (40, 47.5 or 55°C) as independent variables. From the obtained samples, microbiological (aerobic mesophilic and Enterobacteriaceae), physicochemical (pH, soluble solids and cloud index) and enzymatic analysis (polyphenol oxidase and pectin methylesterase) were carried out. Aerobic mesophiles and Enterobacteria inactivation in thermosonicated samples were 4.55Log CFU/mL and 3.85Log CFU/mL, respectively in most of the treatments applied, being influenced by linear terms of amplitude and temperature (p < 0.001). The cloud index was influenced by time term (p < 0.0001); meanwhile, interaction of amplitude * temperature (p < 0.01) and quadratic of time presented significant effect (p < 0.001) on polyphenol oxidase activity. Further, amplitude term had a significant effect (p < 0.001) on the decrease on pectin methylesterase enzymatic activity. The optimal process condition was 77.5% amplitude, 20min and 47.5°C. Thermosonication probed to be effective to control both enzymatic activities in treatments with high amplitudes combined with moderated temperature treatments. Based on this, the use of thermosonication is a viable alternative for fruit-based beverage preservation, that may employ perishable regional natural products offering them an added value.