If you love to save money and catch great deals at the grocery store, then you definitely know it’s possible to pay next-to-nothing for items that are approaching their “best by” or “expiration” dates. Everything from fresh bread and chips to milk and ground beef can be purchased for a fraction of the original cost if that date imprinted on the packaging is about to arrive or has already passed. So what exactly do those dates indicate, and how important are they?

Understanding the Language

Every single year, about $162 billion worth of food is discarded in America alone, largely because consumers incorrectly assume products have gone bad. Labels ranging from “use by” and “best before” to “sell by” and “best if used by” can be incredibly confusing and cause misinformed decisions. Believe it or not, food companies are not currently required to use a standard system to date products.

The good news is that the Food Date Labeling Act of 2016 is currently before Congress in order to require specific labels that indicate whether a food is past its peak but still safe, or past its peak and unsafe to consume.

The Art and Science Behind Date Labels

Large food companies often use microbial challenge studies on food products to determine how long they can last on store shelves or in the consumer’s home. This involves adding a pathogenic microorganism, which is one that can make people sick, into a food item and storing the food in conditions similar to what it would experience during transportation, storage, and purchasing. After different lengths of time, the product is tested to determine at what point the level of microorganisms present would have been too high for safety. That data determines the “use by” date to ensure the product isn’t used after it would be dangerous.

Other companies utilize mathematical models using data regarding moisture content, acidity levels, and expected storage temperatures. The model estimates the length of time the product can be considered safe for consumption. Smaller companies who don’t have access to sophisticated technology are more likely to use reference materials or ask food safety experts for advice.

The Bottom Line

Until Congress passes the Food Date Labeling Act, food guidelines are simply general estimates. It is entirely possible that a food is still safe after a date has passed, so check for signs of rotting and mold before throwing away something that could be perfectly usable.