The effect of Fenton's reagent (hydrogen peroxide and ferrous sulfate) and ascorbic acid on the viscosity and molecular weight of gelatin solutions has been studied and compared. Fenton's reagent (0.025 M H 2 O 2 and 0.0025 M FeSO 4 ) 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 o 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 M w was observed at the temperatures and times used.