What is the shelf-life of a product?
The Shelf-life of a product can be defined as a group of microbiological, chemical and sensory tests performed on food products that determine at what point in time is the product no longer safe to consume and when the product losses its peak quality markers. Further to the above, the Shelf life is a guide for the consumer of the period of time that food can be kept before it starts to deteriorate, provided any stated storage conditions have been followed. The storage conditions are particularly important in the shelf-life of the product and can either be refrigerated, frozen or ambient depending on the product.
The length of the shelf-life of a product is dependent on the following factors:
- The types of ingredients
- Manufacturing process
- Type of packaging
- Storage conditions
The shelf-life is indicated by labelling the product with a date mark, which can either be a “best before” or “use by” date, depending on the product.
How is the shelf-life of a product determined?
The shelf life of a food product begins when the product’s processing and packaging is complete and is ready to be distributed. By performing shelf-life testing, you are able to accurately define dates for your products, ensuring that the quality remains acceptable and safe for consumers.
There 3 key areas of testing involved with shelf-life tests.
Microbiological shelf-life tests
The most critically important is the determination of the microbiological safety of the product. In other words, are there any ‘germs’ in the product that can cause food poisoning. In addition, testing for food spoilage ‘germs’ is integral to the shelf-life tests which tell us at what point does the product exceed the limit of allowable ‘germs’ to the point that it is no longer safe to consume.
Chemistry Quality Tests
The second key area in shelf-life testing involves food quality chemistry. These tests help determine the ‘freshness” of the product including moisture content (at what point does the product dries out), acidity levels, pH and so on.
Sensory and physical tests
During the shelf-life of a product, the food should remain safe to eat, maintain its appearance, odour, texture and flavour. This covers the third key area of the tests, sensory and physical evaluation. A panel of experienced laboratory technicians can perform ‘taste tests’ to determine whether the product maintains expectations throughout the expected shelf-life.
Why Is Shelf-Life Testing Necessary?
A shelf-life test can only be valid for the specific set of ingredients, packaging, and processing of that particular product. It is therefore wise to have finalised and completed the recipe and processes before undertaking a shelf-life study. If changes are made to any step in the process, a set of tests needs to be undertaken.
The need for shelf-life tests came as a result of the availability of ready-to-eat food that have extended shelf-life in our retail environment. The improved science of quality around extending the life of the product, meant that measures needed to be in place to minimise the potential for microorganisms to be present in foods in hazardous numbers.
These safety measures became critical to the food industry and to consumers. The tests used also help identify potential problems in production and reduce the risk of product recalls, ultimately increasing profitability.
Complying to legal requirements
Legal requirements regarding date markers
The food laws throughout the world, have a common ground in determining if and which dates should appear on product labels. The below specifically relates to the use by or best before dates:
- “Use by” date: to be mandatory on perishable pre-packaged foodstuffs and a prohibition regarding the sale thereof after the date has expired as it relates to the safety and/or suitability of the products in question, i.e. microbial growth
- “Best before” date: to be mandatory for non-perishables but no prohibition regarding placed on the sale thereof after the date has expired in view of it relating only to the optimum freshness, thus quality aspects, of these products.
It is therefore absolutely critical that the microbiological safety of the product be determined.
Who is responsible for calculating a shelf life?
Any individual or company who sells or packages food intended to be consumed is required by law to measure the shelf-life of their product. The food label is required to display the result of the tests, ie. “use by” or “best before” dates, as well as the storage instructions.
Refrigerated Shelf-Life Testing
The typical shelf-life of refrigerated products range from 3 to 14 days depending on the product. Samples are stored in the fridge at a maximum of 5°C and tested for stability using the 3 key areas of testing, which include regular testing for spoilage organisms as well as pathogen screening. Trials can continue beyond the targeted shelf-life unless the product fails earlier.
Frozen Food Shelf-Life Testing
The typical shelf-life of frozen products range from 3 to 6 months, and in some cases up to 1 year depending on the product. Such shelf-life tests are lengthy because of the viable duration of the product. Frozen foods do eventually deteriorate during storage and are mostly quality related. However, research has shown that some bacteria are able to survive when extensive temperature abuse takes place. Such as Listeria monocytogenes.
Ambient Shelf-Life tests
Shelf-stable food (ambient food) are products that can be safely stored at room temperature in a sealed container. This includes foods that would normally be stored refrigerated but which have been processed so that they can be safely stored at room or ambient temperature for longer shelf life. The typical shelf-life of refrigerated products range from 6 months to 2 years depending on the product. Fortunately, these tests can be “accelerated” by keeping the product in an incubator (37° C or 98.6°F). One week in the incubator equals one month of shelf-life.
Understanding the end of shelf life
What constitutes the end of shelf life?
Microbiological testing indicates that when the presence of spoilage organisms grow to a level beyond acceptable limits, the product has expired. This endpoint is further defined by relevant food legislation and guidelines provided by government or professional organisations or accepted industry practices.
This endpoint is further supported by quality and food chemistry tests. These acceptability limits are often chosen based on the food industry and sensory perception as an indicator of product failure. Product acceptability can be determined when there is a significant change in the quality in the ageing sample compared to a fresh sample by using comparative testing. Sensory and physical testing (such as odour, taste, appearance and texture) can help demonstrate this endpoint.