They have taken on mythic proportions in the American culture, but do we really understand the implications of expiration dates? Nicola Temple describes the contribution of expiration dates to increasing food waste in Best Before as has Tristram Stuart in Waste. Do these dates serve a useful purpose or do they do more harm than good? One perspective is offered by the comedian Jerry Seinfeld. “How do they know it is that it is definitely that exact day … and then it is sooo over!” Here are some common misconceptions:

That exact day. Expiration dates are about a gradual loss in quality of a food over time. Such loss is on a continuum and not off a cliff. Fresh fruits and vegetables tend to lose quality rapidly, show visible symptoms of spoilage and frequently do not have expiration dates. Expiration dates for packaged products are estimated by predicting quality loss over time and establishing a point before the food becomes unacceptable. The expiration date for a perishable product like milk is set before it is expected to develop off flavors and assumes that the product will be kept at refrigerated temperatures. More stable products lose quality slowly over a longer time, and the expiration date is much less certain. Rather than an exact day, a range of days could be given, but the first day in that range is likely to become the de facto expiration date. Many consumers appear to have trouble with uncertainty.

Quality not safety. Most people believe that expiration dates are about safety, but, for the most part, these dates are about quality. Processed foods are designed to spoil before they become unsafe. By spoilage we mean that they develop an unacceptable appearance, odor, flavor, or texture. The purpose of the expiration date is to warn the consumer to eat the product before it becomes noticeably spoiled. Setting an expiration date too early will lead to discarding of a product well before it becomes unacceptable and thus increased food waste and a loss of money by the company. Setting an expiration date too late runs the risk of dissatisfied customers and failure to repurchase the product. For some items, such as luncheon meats, safety may be of some concern, but spoilage is of much more concern for most products. Generally speaking if it looks good, smells good, tastes good and has an appealing texture it is not spoiled.

Although products are designed to spoil before they become unsafe, mixing of different ingredients and improper handling can lead to unsafe foods. Temperature management is critical to prevent food poisoning. A food may look good, smell good, taste good and have an appealing texture but still be unsafe. Keeping hot foods hot and cold foods cold is a way to prevent the growth of microbes in foods that can make us sick. Preventing cross contamination such as mixing raw meats with cooked foods is another practice that should be observed in a safe, home kitchen. Helpful guidelines for food safety include CLEAN, SEPARATE, COOK and CHILL.

Freshness vs. Wastefulness. There are two competing visions of what we want in an expiration date. We want an item that is fresh and we want one that is safe and of good quality. Authors like Temple and Susan Freidberg in Fresh want to know how fresh an item is when purchased. The fresher the better. Temple calls for a “cut on” date for fresh foods. That helps the consumer get the freshest item, but it greatly magnifies waste. Given a choice, most consumers will go for the latest cut-on date. That means items with the earliest cut-on dates will sit around until they need to be tossed.

Transparency is not always a good thing as perception of freshness can lead to increased waste. Preventing food waste depends on less rather than more information, particularly if that information is not really relevant to quality. What happens in the field, maturity at harvest, handling and storage conditions could also affect the quality of a fresh fruit or vegetable, but a cut-on date and appearance are the only guides to the shopper. Remember “born on” dates for beer? That did not work out so good as beer connoisseurs went for the freshest, and older ones were wasted.

Protecting company reputation. Some companies, such as producers of snack chips or bread, pull their products off the shelves before the printed expiration dates. These are companies who have store delivery persons who stack fresh products in the stores and pull items still on the shelves. The idea is that they don’t want their customers biting into a stale product and become less interested next time they see that product in the store. Hopefully some of these pulled items make it to a food pantry. Many of these products, unfortunately, are just discarded.

A solution? Food engineers came up with a solution many years ago. They proposed placing a time-temperature indicator on the package that would change colors, such as green OK, yellow consume it within a reasonable amount of time, and red do not consume. The transition from green to yellow would be before a typical expiration date and from yellow to red after that date. To an engineer that solved “that exact day” problem posed by Seinfeld, but there are at least two problems with the concept. Companies don’t like it because of liability concerns. Can green and yellow colors be considered to assure safety? Could a customer return it for a refund when the indicator turns red? Also, would the consumer make the green-to-yellow transition the de facto expiration date thus increasing food waste? Some of these indicators are now available with a cell phone app. For the most part, they have not caught on. If they are so good, why have I never seen any on food products?

As long as we associate expiration dates with safety, too much food will be tossed before it is consumed. As long as we collectively demand the freshest product and are given a date that may or may not be directly relevant to food quality or safety, too much food will be wasted. The whole idea of food preservation and the use of preservatives in foods is to slow down the spoilage process giving us more time to store them, consume them on our own schedule, and minimize waste. For the most part expiration dates merely serve as guidelines to allow us to consume an item before it loses sufficient quality. Food processing has been remarkably successful in preventing waste of raw foods throughout history. Expiration dates can give us a clue as to when we should eat a food before it becomes unacceptable, but they can also lead to excess food waste.

Next week:  What happened to public trust in science? Is this a crisis for the food system? a guest post by Dr. Daryl Lund, Professor Emeritus, University of Wisconsin-Madison