A common indicator of food contamination is food that has a strange odor or color. When food spoils or becomes contaminated, its chemical composition changes, often leading to noticeable alterations in smell and appearance. For example, off odors can indicate the presence of bacteria, spoilage, or the breakdown of food substances, while unusual colors might suggest mold growth or chemical reactions. These sensory changes are important for consumers and food handlers to recognize as they can indicate that the food is no longer safe to eat.
Other factors, such as food in a sealed container, can prevent contamination, while food kept at room temperature may not be safe if left too long but does not inherently indicate contamination. Freshly prepared food is typically safe but can become contaminated if not handled properly. Thus, observing for unusual odors or colors is a key practice in identifying potentially hazardous food.