Discuss information on bacteria and molds while waiting for the yeast to grow. Under the right conditions, a few bacteria can very rapidly become millions. When they have food and the right environment, bacteria begin to grow, and each one soon divides into two bacteria. These two each quickly divide, and so do the bacteria they produce. Within 2 to 3 hours, a few bacteria on certain foods can grow into thousands or millions, enough to make someone sick.
Many bacteria grow best at room temperature with food and water available.
Bacteria often live best on high-protein foods that are moist or watery like dairy products, meats, eggs, fish, and poultry. To keep these foods safe, they must be stored in a refrigerator or freezer. Heat or cooking will kill many bacteria, but it's wise to store foods safely even if they will be cooked.