Glutathione is present in flour and is also produced by yeast cells. Although its function is normally a positive one, in dough it actually weakens the gluten that the bread relies upon to trap carbon dioxide gas and expand during fermentation. Fresh flour is oxidised before it is packaged and sold in order to reduce the glutathione content and improve the gluten-forming quality of the product. See also ascorbic acid.
Want to find out more? Look at the chapter on ingredients in the book flour and water.
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