Ascorbic acid is a weak acid. Vitamin C is a form of ascorbic acid. In regions (including the UK) where chemical bleaching of flour is prohibited, ascorbic acid is added as an oxidising agent to freshly milled flour, which would otherwise lack strong gluten and produce a crumbly dough. Freshly-milled or 'green' flour was traditionally oxidised or 'matured' by storing it in contact with air for a period of time before it was sold but, with the expanding populations of the 19th century and increased demand, this practice was considered impractical and chemical means of speeding up the process were developed.
Want to find out more? Look at the chapter on ingredients in the book flour and water.
Back to the glossary.