Effect of the Processing Temperature on the Degradation of Food Flavonoids: Kinetic and Calorimetric Studies on Model Solutions

Abstract

Food flavonoids have a high antioxidant activity that make them bioactive to fight oxidation. However, when they are used in different formulations, these bioactive molecules are often the subject of at least one heat treatment step such as cooking, pasteurization. To establish the sensitivity of these molecules to heat treatment, the kinetics of degradation of 4 flavonoid extracts were evaluated under isothermal and non-isothermal conditions. The flavonoids tested belong to the aglycon (eriodictyol and mesquitol) and glycosylated (rutin, naringin) forms. The glycosylated flavonoids have a higher stability than the aglycons. Among the glycosylated flavonoids, rutin is more sensitive to heat than naringin because of the different degree of hydroxylation between these 2 compounds. For the aglycon form, the sensitivity to heat varies depending on the absence or presence of a carbonyl group at the 4-position and a hydroxyl at the 3-position. The addition of 10% of propylene glycol causes an effect protector delaying the thermal degradation of flavonoids. Activation energies are also affected by both the flavonoid structure and the heat treatment system. The differences observed between the isothermal and non-isothermal conditions can be attributed to the difference in heating intensity that can generate a difference in the composition of the solution. The evolution of antioxidant activity of flavonoid solutions after heat treatment is different depending on the structure of the flavonoid studied.