Things you need to consider when setting a shelf life
By Linda Everis - 25 July 2017
The shelf-life of a product is the time that it remains acceptable to eat. Within the shelf life the product will remain safe and retain the desired sensory, chemical, physical and microbiological characteristics.
Understanding shelf life is essential in assuring the safety and quality of the product. It’s important to re-evaluate shelf life when products are reformulated because changing or reducing levels of salt, sugar or preservatives can all impact on shelf life.
What influences shelf life?
Shelf life is influenced by many aspects of good manufacturing practice and product formulation. Combinations of these factors are often used together to inhibit microbial growth, and so manage microbiological shelf life. This is known as hurdle technology.
Raw materials introduce microorganisms and sensory attributes to the final product. Variation in the raw materials will cause these attributes to vary in the product and may affect the shelf life. For example, coleslaw made using freshly harvested cabbage will have a lower count of yeasts than cold-stored cabbage and therefore will have a longer shelf life. It’s also important to consider if there are any in-house or external specifications you need to follow. You can find advice specifically on how to set microbiological criteria in Campden BRI Guideline 52.
All processing exerts considerable changes on the microflora and the chemical, biochemical and sensory properties of food. Small changes in one type of processing may have a large effect on the properties of the food and may be critical for shelf life – for example, in cottage cheese, small changes in pH in the range 4.5-5.5 can significantly affect the types of spoilage micro-organisms that can grow. More importantly, such changes would allow growth of pathogens should they survive the process or subsequently contaminate the product.
Intrinsic properties of the product such as pH, salt and water activity - which have been identified as critical to product stability - must be achieved, to ensure that all product made within specification will conform to the final shelf-life claimed for the product.
Storage and distribution
How a product is stored during both transport and retail display will greatly affect shelf life. Storage temperature has the biggest effect, but light and humidity will also influence shelf life. Customers may have different requirements for the temperature and duration that the product will be stored at. Therefore it’s possible that one product may need to have more than one shelf life if the manufacturer has more than one customer.
Poor hygienic control may result in high levels of organisms being introduced to the product, which may have adverse effects on the safety and quality of the product and thus affect its shelf life – for example poor cleaning of meat slicing equipment will increase microbiological counts and reduce the shelf life of cooked meat.
Modified gas atmospheres introduced at the time of packaging or developing on storage will influence microbial growth and enzymatic and chemical reactions. Similarly, light, gas and packaging material permeability will influence the shelf life.
How the consumer purchases, stores and uses the product will affect the product’s shelf life. For example, how long the product stays in the fridge in-store and is being transported to their home. And once the product is taken home, how it’s stored - for example a juice may not be returned straight to the fridge, the carton may be left on the table for periods.
The shelf-life of food products is influenced by microbiological, chemical and sensory considerations and, in some cases, legislative requirements. Shelf life needs to be determined by following sound scientific principles that can take into account all the relevant formulation, manufacturing, distribution and storage factors. Assigning the correct shelf-life can be the key to the commercial success of a new product and should be done in the early stages of new product development.
If you want to learn more about shelf life testing and how to approach shelf life testing then you can contact Linda Everis. You might also be interested in our Guideline Evaluation of product shelf-life for chilled foods.