Continuous Ohmic Heating Assisted Isothermal Treatment of Standardized Pineapple Juice: Its Effect on Bromelain Inactivation, Vitamin C Degradation, and Their Kinetic Modeling

Abstract

Continuous ohmic heating (COH) is an electro-resistance heating and an efficient emerging tool for fruit juice processing. The current work investigated the effect of COH parameters like electric field strength (EFS: 30–40 V/cm), temperature (70°C–90°C), and isothermal holding (0–60 s) on bromelain activity and vitamin C in standardized pineapple juice (22°Brix/Acid). The accuracy factor (A_f), bias factor (B_f), statistical parameters, and Akaike information criteria (AIC) were used to compare different kinetic models like first order, Weibull distribution, and logistic model and to choose the best-fit kinetic model for bromelain inactivation and vitamin C degradation. The results showed that COH parameters significantly affected bromelain activity and vitamin C. A minimum bromelain residual activity and vitamin C content in the COH-treated juice were 1.2% ± 0.4% and 38.2% ± 2.6%, respectively, when treated at 90°C, 40 V/cm for 60 s. The Weibull distribution model (R² > 0.99; RMSE < 0.0293; ∆_i ≤ 2) described bromelain inactivation kinetics better than other models, while the first order model (R² > 0.84; RMSE < 0.057; ∆_i = 0) was best suited for vitamin C degradation kinetics. The A_f and B_f for respective models of bromelain inactivation and vitamin C degradation were closer to the simulation line (closer to 1), suggesting the accuracy of these models in predicting. Thus, the Weibull and first-order models are good tools for predicting bromelain inactivation and vitamin C degradation in COH-treated standardized pineapple juice.