What is the difference between spoilage organisms and harmful pathogens?

I get asked a lot if you can get sick from eating moldy (spoiled) or expired food. There is a common misconception that a food is considered harmful if it’s consumed past its “sell by” or “use by” date. Though some foods become undesirable due to off odors, flavors or colors, there are other shelf stable foods that would be safe to eat, even past their expiration date. Much of this has to do with how a food is processed, packaged, stored and components of the food itself.

But how can a food be spoiled or expired but not cause illness? The difference between the two has to do with the types of bacteria growing in the food. Typically when people are seeing mold, slime or color changes this is due to spoilage bacteria, which are not harmful when consumed – but definitely is undesirable. The real danger comes from pathogenic bacteria, which don’t normally cause a change in the characteristic of the food so the consumer is unable to detect it by smelling, tasting or visually examining the food. Pathogenic bacteria include listeria monocytogenes, E. coli O157:H7, Clostridium botulinum and Salmonella.

Spoilage bacteria will eventually grow on any food as foods provide ample nutrients for microorganisms to proliferate. Pathogenic bacteria, however, can enter the food product due to mishandling or poor sanitation practices. If a food containing pathogenic bacteria is subsequently held at improper temperatures, bacteria can quickly multiply. Large numbers of pathogens present in a food cause illness if consumed. There are also some bacteria that can produce a harmful toxin not destroyed bot cooking.

This is why it’s critical to practice sanitary handling procedures, store food at proper temperatures and cook foods to minimum safe internal temperatures to ensure pathogenic bacteria are destroyed. The minimum internal temperature varies depending on the food type. Some instructions might say to cook until the product is “hot”, but it’s important to quantify the temperature. After cooking, foods must be consumed, held above 140 degrees F or quickly cooled and stored below 40 degrees F.

Storage is also extremely important to consider. Foods that need to be refrigerated such as meat, poultry and seafood must be stored below 40 degrees F to inhibit bacterial growth. There also must be adequate separation between food products in a refrigerator so cool air can circulate freely. In addition, raw foods must be kept below cooked foods so raw juices do not contaminate the cooked product. Lastly, it’s critical to monitor the actual temperature of a refrigerator unit and not just go by how the temperate may “feel”.

So while it is not advisable to eat spoiled food, these foods are less likely to cause illness beyond the “yuck” factor. Foods that seem fine can cause illness. There is also another distinction which is becoming more important and that is whether or not “use by” dates indicate anything about safety. This is usually there for quality and indicates how “fresh” a product may be. This can often lead to waste. But the best ways to maximize food safety are through proper handling, storage and thorough cooking.