Shelf life is a measure of food deterioration and spoilage during storage and distribution. Simply put, how long is the product safe and acceptable to consume? Many factors play a part in determining the shelf life of a food product. These factors are a combination of physical, microbiological and chemical processes, triggered by various factors. Factors include product attributes, quality and consistency of ingredients, the moisture content and acidity levels. Also playing a part are external factors like storage, transport and packaging materials. It is important in any shelf life test design that all these factors are taken into consideration as much as possible. The goal being that the product’s end shelf life is determined to be when the product no longer delivers the same high-quality eating experience to the consumer as when the product is fresh.
The shelf life of a food product begins at the time the it was manufactured or prepared.
Questions to Answer to Determine Test Design What is the Desired Shelf Life of your product? How much time is required for your product to be produced, distributed, sold and lastly consumed. How many days/weeks/months would that be?
What are the Storage Condition(s) that your product will experience? - What is the storage condition will your product experience throughout its shelf life? Is it refrigerated, frozen or stored at room temperature. Do you want to test for the worst-case scenario or expected storage?
How many Samples of Product Will I Need for Testing? Determine how often you want to check your samples. The shorter the shelf life, the more frequent you will want to test your products.
tip: Divide the total weeks of testing by how often you'll be checking it and have AT LEAST that many samples.
example: So, for a 24-week study with tests every 2 weeks, you'd need at least 12 samples. Add more samples if micro testing will also be done
What Testing Methods Will Be Used and Who will be Doing the Evaluating? What attributes will you be testing for and who will be involved in the evaluations,
tip: this is typically done by a 3-5-person panel that will meet on a consistent basis.
Setting Up your Test
Secure “Gold Standard” and refrigerate it
tip: The “Gold Standard” is product that is freshly made and represents desired sensory characteristics of taste, texture, color and aroma. This is your control and all future evaluation will be compared to your gold standard. Secure the same number of Gold Standards (also known as “Control” samples) as you will have test product. Evaluate Sensory Characteristics as compared to your Gold Standard. What are the physical attributes of the product that are acceptable and unacceptable. These must be established and understood by evaluator
Taste: How has this changed from control, what words will we use to describe acceptable and unacceptable tastes?
Texture: Does texture change during shelf life? If so what happens? Separation, product thinning out etc.? What words will we use to describe unacceptable texture changes?
Color: What is an undesirable color?
Smell: What are the objectionable odors that develop as product ages. What is considered unacceptable? Will descriptors such as rancid, sour, oxidized etc. be used?
Microbiological Characteristics as compared to your Gold Standard.
In many cases the objectionable changes in a product over its shelf life is contributed by the growth of yeast, mold and or bacteria. Sometimes the bacteria level increase to an unsafe level to be consumed.
It is important in some cases to include microbiological testing along with sensory testing in order to determine a proper shelf life for your product. Considerations to make:
Suggestion: Your control or “Gold Standard” product should be tested to determine baseline levels for:
pH
Water Activity
Salmonella
E. coli
Staph. Aureus
Aerobic Plate Count
Listeria
Mold
Those baseline levels will be used as a comparison to determine any rapid growth of bacteria that might affect shelf life determinations. One must decide what analytical testing will be done for each product testing interval.
Last tip:
Once you have established the initial shelf life, you still need to routinely check that the food product is maintaining that food expiration date.
Whenever there is a change in ingredient, process or packaging a new shelf life study should be initiated.
Shelf life determination is important. If you are selling your food product in a retail environment; then at some point, you should strongly consider getting shelf life testing to give your product a valid expiration date.