Thermal Kinetics of Gamma–Aminobutyric Acid and Antioxidant Activity in Germinated Red Jasmine Rice Milk using Arrhenius, Eyring-Polanyi and Ball Models

Abstract

The thermal kinetics of changes of –aminobutyric acid (GABA) and antioxidant activity (DPPH assay) in germinated red jasmine rice milk (GRJM) at heating temperatures of 80, 90, 100 and 121C using Arrhenius, Eyring–Polanyi and Ball models was examined in this study. Under isothermal conditions, the increasing of heating temperature from 80C to 121C resulted in the decreasing of GABA. However, DPPH radical scavenging activity increased under temperature range of 80–100C, but decreased at 121C. The highest residue of GABA was 94% after heating at 80C for 30 min, while the highest increasing of DPPH radical scavenging activity was 230% at 90C for 30 min. Thermal degradation of GABA followed a second–order reaction kinetic, while the increasing of antioxidant activity (80–100C) followed a first–order kinetic as well as the degradation of antioxidant activity (121C). The heating temperature dependence of rate constant for degradation of GABA and increasing of antioxidant activity were described by Arrhenius, Eyring–Polanyi and Ball models. Following the Arrhenius law, activation energies were 59.62 kJ/mol and 30.31 kJ/mol, respectively for degradation of GABA (80–121C) and increasing of antioxidant activity in GRJM (80–100C). Arrhenius, Eyring–Polanyi and Ball models could be used to predict accurately GABA content and antioxidant activity in GRJM during isothermal heat treatment.

Green micellar stability‐indicating high‐performance liquid chromatography method for determination of rupatadine fumarate in the presence of its main impurity desloratadine: Oxidative degradation kinetics study

“…At 60 and 80°C, the best‐fitted linear regression and highest R 2 were obtained when Ln(C t /C 0 ) was plotted versus time proving RUP follows a first‐order kinetics at these temperatures. The degradation rate constant (K), time left for 50% potency ( t 1/2 ), and time left for 90% potency ( t 90 ) were calculated in Table 3, taking into consideration that reaction occurs in the presence of excess H 2 O 2 under aerobic conditions, thus RUP follows pseudo‐first order kinetics rate [46].…”

“…F I G U R E 2 Chromatograms of alergoliber tablet (100 μg/ml) (A) and alergoliber syrup (100 μg/ml) (B) using the proposed micellar HPLC method. (t 1/2 ), and time left for 90% potency (t 90 ) were calculated in Table 3, taking into consideration that reaction occurs in the presence of excess H 2 O 2 under aerobic conditions, thus RUP follows pseudo-first order kinetics rate [46]. Nevertheless, at 40 • C the best-fitted linear regression and highest R 2 were obtained when 1/(C t /C 0 ) was plotted versus time, which indicated the reaction might follow a second-order kinetics rate.…”