Bread may be unfit for use from being made of adulterated or too old flour, from turning sour from bad flour developing excess of lactic acid, from becoming bitter from yeast, from becoming sodden from insufficient fermentation or aeration, and it may grow mouldy from exposure to air when it is too moist.

"Most of the diseases of the War of 1812 were due to defective food, and in 90 per cent of the cases the flour was at fault. In the War of the Rebellion similar reports were often received " (Woodruff).