Ndiaye Khady^{1, 2}, Kane Cheikhou^1,, Ndoye Mouhamed¹, Ayessou Nicolas², Cisse Mady², Diop Codou Mar¹

The numerous benefits of anthocyanins from Hibiscus sabdariffa L on human health explain all the thermal and athermal preservation techniques undertaken so far. However, these methods result in considerable losses of anthocyanins, leading to a deterioration of the nutritional and organoleptic qualities of the product during storage.Platinum electrode oxygen reduction is a new athermal technique using a two-compartment electrolysis cell separated by a cationic membrane. The fruit juice is stabilized by passing the reduction current for a set time. The electrochemical approach is a new technique for cold juice without additing chemical molecules. Reaction kinetics in Hibiscus sabdariffa juice follows 1st order kinetics. The classical Arrhenius, Ball and Eyring models used showed the degradative effect of dissolved oxygen in the juice with a significant difference (Ea = 4000 J/mol) between the activation energy of the electroreduced extract and the control (untreated). This is corroborated by the values of the half-reaction time which are 24 S-1 for the electrochemically treated extract and 20 S-1 for the untreated control after 5 months of storage at 4°C.The value of the enthalpy of activation of the electroreduced juice about 6 J/mol/K and that of the control 5,72 J/mol/K shows that the electrochemical process takes place at low energy, i.e. 0,28 J/mol/K for a volume of about 250 ml.The various kinetic models have also confirmed by the electrochemical approach that the temperature factor predominates over the dissolved oxygen factor. At 37°C, the half-reaction time is 1,3 s-1 for the electroreduced Hibiscus juice as for the untreated extract after 5 months of conservation.

Modelling, Hibiscus sabdariffa, anthocyanins, oxygen, conservation, Electroreduction, kinetic