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
One of the critical updates to the Food Labelling and Advertising Regulations R146 was the inclusion of regulation regarding the date markers.
The law states:
- “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.
Enzymes, which can cause flavour change (lipoxygenase) in non-blanched fruits and vegetables and accelerated deterioration reactions in meat and poultry (enzymes released following disruption to organelle membranes during precooking) are a big concern for frozen foods.
Food Safety and Inspection Service, United States Department of Agriculture
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 temperature range). One week in the incubator equals one month of shelf-life.
Understanding the end of shelf life
What constitutes the end of shelf life?
We know from our microbiological testing 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. Our sensory and physical testing (such as odour, taste, appearance and texture) can help demonstrate this endpoint.