Ascorbic acid and hydrogen peroxide (Fentonʹs reagent) induced changes in gelatin systems

The effect of Fentonʹs reagent (hydrogen peroxide and ferrous sulfate) and ascorbic acid on the viscosity and molecular weight of gelatin solutions has been studied and compared. Fentonʹs reagent (0.025 M H2O2 and 0.0025 M FeSO4) lowered the activation energy for depolymerisation of gelatin (49.3 kJ/mol) compared with heat degradation without additives (72.8 kJ/mol). Ascorbic acid (1%) showed no change in the gelatin viscosities compared to the control when heated in dilute solution (15 g gelatin in 100 ml water). In contrast, storing gelatin powders containing ascorbic acid at 80 °C for 6 h at different relative humidities (moisture contents of 8.7–48% dry basis) caused an increase in molecular weight as assessed by SEC/MALLS. Protein solubility decreased and browning colour intensity increased at RHs of 50% and higher. The greatest changes occurred at RH of 50% where 40% of the gelatin was not soluble in water or 1% sodium dodecyl sulfate. These changes could be due to Maillard cross-linking, however, at moisture levels that equated to the gelatin polymer being in the glassy state no change in Mw was observed at the temperatures and times used.