Shelf-life can be described as the period of time under defined storage conditions, after manufacture or packing, for which the food will remain safe and fit for use. 'Safe' is referring to the the the composition of the product, or the microbial contents not being at a level harmful on consumption. 'Fit for use' is referring to the need for the food to retain its desired chemical, physical, functional, organoleptic (sensory) and microbiological characteristics, including complying with any nutritional labelling specified on the product.
Use-by dates are determined by the manufacturer/packer during the development of any food product, and this is achieved through scientific knowledge, methodology and testing. Use-by dates on food specifically relate to food safety, and are a legal requirement for foods that deteriorate quickly.
In order for use-by dates to be a valid guide, consumers are expected to follow the storage instructions displayed on the product packaging.
Best Before Dates
Best before dates are about food quality and not safety. Once the best before date has passed, its organoleptic properties (such as flavour, aroma, texture) may deteriorate to a noticeable degree.
Frozen, dried and tinned foods typically use best before dates, however similar to use by dates, the accuracy of this is reliant on food being stored according to the instructions on the packaging.