A stoichio-kinetic model for a DPPH -ferulic acid reaction.

Estimates of the activity of antioxidants in the literature often appear inconsistent. In the specific case of the DPPH test, the diversity of measurements may arise from variations in the protocols followed. This paper proposes an unbiased method which models the reduction mechanism.

Kinetic modelling of ascorbic and dehydroascorbic acids concentrations in a model solution at different temperatures and oxygen contents.

The degradation kinetics of vitamin C (ascorbic and dehydroascorbic acids, AA and DHA) were determined under controlled conditions of temperature (50-90 °C) and oxygen concentrations in the gas phase (10-30% mol/mol) using a specific reactor. The degradation of vitamin C in malate buffer (20 mM, pH 3.8), mimetic of an apple puree, was assessed by sampling at regular intervals and spectrophotometric quantification of AA and DHA levels at 243 nm.

Spectrophotometric method for fast quantification of ascorbic acid and dehydroascorbic acid in simple matrix for kinetics measurements.

A simple, rapid and reliable method was developed for quantifying ascorbic (AA) and dehydroascorbic (DHAA) acids and validated in 20mM malate buffer (pH 3.8). It consists in a spectrophotometric measurement of AA, either directly on the solution added with metaphosphoric acid or after reduction of DHAA into AA by dithiothreitol.

Thermal degradation of folates under varying oxygen conditions.

Folate losses in thermally treated foods are mainly due to oxidation. Other mechanisms and folate vitamers behaviour are poorly described. Our study evaluated oxygen impact on total folate degradation and derivatives' evolution during thermal treatments.

Modelling the interactions between free phenols, L-ascorbic acid, apple polyphenoloxidase and oxygen during a thermal treatment.

The kinetics of degradation of chlorogenic acid (CG), (-) epicatechin (EPI), L-ascorbic acid (AA) and polyphenoloxidase (PPO) activity from Marie-Ménard apple in pH 3.8 solutions at 20 and 50°C were investigated to provide information on the impact of the presence of CG, EPI and/or AA on PPO thermostability. The effect of the heat treatment on their degradation by enzymatic and/or nonenzymatic ways was also studied.