Chemical Fate of Ascorbic Acid in Wheat Flour Extract: Impact of Dissolved Molecular Oxygen (O2), Metal Ions, Wheat Endogenous Enzymes and Glutathione (GSH)

Ascorbic acid (AH₂) is a commonly used additive in food products. In wheat breadmaking, it is, for example, added to flour for its dough strengthening and bread volume-enhancing effects. While these bread property-enhancing effects are well known, the final chemical fate of AH₂ in breadmaking applications remains nearly undocumented. This study tries to shed light on the chemical fate of AH₂ in wheat breadmaking by investigating the chemical and enzymatic conversion of AH₂ and its reaction products using ¹³C NMR spectroscopy in combination with AH₂ labelled with ¹³C on the C₃ carbon. Following the chemical conversion of AH₂ as function of time, in ultra-pure water, tap water, and wheat flour extracts, in the presence and absence of dissolved O₂ and glutathione (GSH), the specific impact of the presence of trace metal ions, dissolved oxygen and endogenous GSH on the oxidation of AH₂ could be elucidated.