Propionates such as propionic acid and calcium propionate, and sorbates such as sorbic acid and potassium sorbate are used in bread to prevent growth of mold. The effectiveness of these preservatives in retarding mold growth depends on the pH of the dough and the correct amount of preservative used.
The pH of the dough must be lower than 5.2 when using propionates, whereas it must be in the range of 5.0 to 6.0 when using sorbates. In some yeast products, citric acid or vinegar is used to lower the dough pH to the desired level. Only small amounts of preservatives are used in bread because high levels may retard yeast activity, extend the proofing time of the dough and affect the flavor of the baked bread.