Optimization of ultrasound-assisted osmotic treatment of Aleo vera gel impregnated with grape pomace phenolic compounds using response surface methodology

Abstract

This study was focused on investigating the use of pulsed ultrasound-assisted osmotic dehydration (UAOD) for enhancing the infusion of phenolic compounds extracted from grape pomace (GPx) to Aloe vera (Aloe barbadensis Miller,) gel (AVG) using response surface methodology (RSM) and produce a dehydrated product with high antioxidant content. Fresh AVG were initially immersed in a sucrose solution of 50° B with three levels of GPx (10, 20, and 30 v/v) and subjected to pulsed ultrasound (US) treatment with a probe of 2 cm diameter, two levels of ultrasound amplitude (UA) (50 and 100%), and three ultrasound treatment times (UT) (30, 135 and 210 min). The pulsed on and off times were set at 15 and 1 min, respectively. A multiple regression analysis was carried out to develop second-order polynomial models with high coefficients of determination value (R² > 0.81). The optimal conditions were obtained using the Design Expert software. The best condition obtained for the UAOD optimization was UA = 59%, 20% grape pomace extract in 50% sucrose, UT = 173 min to result in a moisture loss of 51.3 % (predicted 49.9%), solid gain of 4.3 % (5.0%), total phenolic contents of 30.5 mg/g (31.8%), and DPPH radical scavenging activity of 15.3% (15.0%). UAOD therefore appears to be a promising process for antioxidant incorporation and preparing added value product.