Fact Sheet

CSIRO is helping provide healthier, high quality foods to match consumer and industry preferences.

The shelf life of foods

Background

The legal requirement for manufacturers of packaged foods to open date mark foods was introduced in Australia in 1978.

This followed similar moves internationally and the publication of a standard by the Codex Committee on Food Labelling.

It was argued by consumer groups that with the rapid changes occurring in food manufacturing, packaging and retailing that consumers could no longer rely on traditional wisdom and habits to dictate how long a food may be stored.

Changes to the requirements for date marking of food have occurred since 1978. The current Standard 1.2.5, Date Marking of Packaged Food of the Food Standards Code (FSC) reads in part: 'the Standard requires packaged food, with some exceptions, to be date marked, and prohibits the sale of packaged food after the expiration of the use-by date, where such a date mark is required'.

A use-by date means 'the date which signifies the end of the estimated period, if stored in accordance with any stated storage conditions, after which the intact package of food should not be consumed because of health and safety reasons'. It is an offence to sell packaged food past its use-by date and this form of date marking is tied to food safety.

The best-before date is the open date which most packaged foods carry and is defined in the FSC as 'the date which signifies the end of the period during which the intact package of food if stored in accordance with any stated storage conditions, will remain fully marketable and will retain any specific qualities for which express or implied claims have been made'.

An exemption from the open date marking still applies if the best-before date of the food is two years or more. However many manufacturers whose products fall into this category elect to date mark these foods.

Whose responsibility?

The responsibility of determining the shelf life of a food, and thus its best-before or use-by date, lies with the manufacturer/packer.

The most direct way of doing this is to conduct properly constructed storage trials under realistic, defined conditions.

This may not be possible for smaller manufacturers, in particular those just entering the market. They frequently are looking for some rapid method to measure and estimate shelf life to allow them to put their product on the market as quickly as possible.

Established manufacturers also are reluctant to rely solely on conventional storage trials to determine shelf life.

Commercial pressures usually mean that a product must be marketed as quickly as possible after its development. Retailers may also have their own demands about shelf life of particular product categories especially those with a relatively short shelf life.

Indirect methods of shelf life determination are frequently used to yield results which otherwise would be time consuming to obtain.

These may involve so-called accelerated shelf life tests usually based on storage of the product at higher than normal temperatures or computer-based models.

While these methods may prove useful, they must be applied with care.

Storage of foods at higher than normal temperatures can induce changes in the food which would not occur at normal ambient temperatures. Also the rate at which normal changes are accelerated by higher temperatures must be known with acceptable accuracy.

Models are useful only if they have been shown to mimic spoilage rates in like foods and not merely been developed under laboratory conditions. These models are not designed to be used beyond the range of data used to construct them.