Metallic components of fruit juices. III.—Oxidation and stability of ascorbic acid in model systems resembling blackcurrant juice

Oxygen uptakes and ascorbic acid losses occurring in model systems resembling blackcurrant juice have been studied using the Warburg technique. Oxidation of ascorbic acid in the presence of copper was significantly increased by additions of small amounts of iron although iron alone had little effect. Of blackcurrant juice components examined, anthocyanins increased, while glucose reduced, the metal‐catalysed oxidation of ascorbic acid. Ascorbic acid losses at pH 2·9 increased according to buffer in the order malonate, citrate, malate, quinate, phthalate, formate and phosphate. The effects of some metal chelating agents are described.