No, you only see part of the mold on the surface of food -- gray fur on
forgotten bologna, fuzzy green dots on bread, white dust on Cheddar, coin-size
velvety circles on fruits, and furry growth on the surface of jellies. When a
food shows heavy mold growth, “root” threads have invaded it deeply. In
dangerous molds, poisonous substances are often contained in and around these
threads. In some cases, toxins may have spread throughout the food.
USDA United States Department of Agriculture
Food Saftey and Inspection Service