How is the expiration date of a product measured?

The shelf life of a food is a period in which it retains the attributes expected by the consumer, under its storage and distribution conditions, making it suitable for marketing.

After shelf life ends, some of the quality attributes such as sensory, microbiological, or physicochemical, may be altered, leading to rejection by the consumer, in addition to the fact that sometimes they may present a potential health risk. Therefore, the person responsible for the preparation of the product must know the shelf life of the food, under the storage conditions suggested by the product, to be able to market it with an expiration date or best-before date, as the case may be.

Difference between "best before" date and "expiration" date

According to Mexican regulations (SCFI/SSA, 2010), the "best-before date" is defined as the date by which the sanitary and quality characteristics that a prepackaged food or beverage, are stored under the conditions suggested by the person responsible for the product, is considered to be reduced or eliminated so that after this date it should not be marketed or consumed. The expiration date, then, indicates the time until which the food is safe, so it is not advisable to consume it after this date.

The expiration date appears on highly perishable foods, such as those made from fish, fresh meat, or milk, among others. It is very important to follow the storage instructions, for example, keep refrigerated or keep frozen; otherwise, the food will deteriorate sooner, and whoever consumes it would be at risk of suffering food poisoning.

If you freeze the food at home shortly after purchasing it, you can extend its shelf life beyond the "use by" date, provided you freeze it properly. However, you must follow the instructions on the package label, e.g., "Keep in freezer until expiration date" or "Once thawed, use within 24 hours".

Once a package with an expiration date has been opened, follow the storage and consumption instructions, e.g., "Once opened, consume within three days," keeping in mind that the food must be consumed before the expiration date has passed.

On the other hand, in the same standard, the "best-before date" is defined as the date on which, under certain storage conditions, expires the period during which the prepackaged food is marketable and maintains the specific qualities attributed to it, but after which the prepackaged product can be consumed. In other words, the best-before date indicates the time until which the food retains the intended quality.

In this case, the food is still safe for the consumer after the best-before date, provided that the storage instructions are followed and the package is not damaged; however, it may begin to lose flavor, aroma, or texture. The best-before date appears on a wide variety of refrigerated, frozen, dried (pasta, rice, etc.), canned, and other foods (vegetable oil, chocolate, etc.).

Before throwing away food that has passed its best-before date, it is advisable to check if it looks, smells, and tastes good, making sure that the container is intact. When opening a package of food with a best-before date, follow the instructions; for example, "Once the package is opened, consume within three days" (Profeco, 2021).

How to protect your health when consuming prepackaged food?

First, before acquiring food, it is necessary to verify that the packaging is not altered or damaged. It is very important to consider that if the package is damaged, the expiration date could be reduced. Try to check the label and make sure that you have not purchased a product with an expired expiration date or one that is very close to expiration.

The recommendation is not to consume any food after the expiration date. Consuming an expired product could expose you to food poisoning. In addition, it is very important to store products at home, under appropriate conditions, according to the instructions on the label.

How is the best-before or use-by date determined?

To establish the best-before or best-before date, it is necessary to determine the real-time shelf life of the product under the conditions in which it will be marketed. This is possible when the product is perishable; for example, a meat or dairy product or fresh pasta that is marketed under refrigeration. However, when the product is not perishable, as would be the case of prepared flour, accelerated shelf-life studies under extreme storage conditions are used.

In both cases, the parameters to be evaluated to determine shelf life are based on sensory attributes (flavor, aroma, texture, or color) that condition its acceptance, microbiological analysis (bacteria, fungi, and yeasts) or physicochemical analysis (pH, compounds associated with rancidity or oxidation, among others).

In the case of canned foods, which are very stable products due to the heat treatment to which they were subjected, accelerated shelf-life studies are necessary. In contrast, to determine the expiration date of refrigerated meat products, it is necessary to track attributes during their shelf life in real time under typical marketing conditions. For bottled beverages, it may also be necessary to subject them to an accelerated shelf-life study, depending on the formulation of the beverage.

Accelerated shelf life determination consists of subjecting the product to extreme storage conditions, which are generally three different temperatures to accelerate the deterioration of the product. In this case, shelf life can be estimated by applying predictive mathematical models (Arrhenius), into which the results of attribute evaluations are input to estimate the behavior of the product under different temperature conditions over time.

Where can I perform shelf-life studies?

The Food and Development Research Center uses both real-time and accelerated shelf life methodologies, where sensory (flavor, aroma, color, and texture), microbiological and physicochemical evaluations are performed to design and execute shelf life projects for products.

By Belinda Vallejo Galland, Aarón González Córdova and Ricardo Reyes Díaz. Source: CIAD