The storage life of foods
This fact sheet discusses ways to prolong the usable life of stored foods.
24 September 2009 | Updated 14 October 2011
Date marking of food products
Most packaged foods, manufactured in Australia or imported, are labelled with a date.
The use of date marking systems is governed by the food regulations.
- 'Best before date' - signifies the end of the period under any stated storage conditions during which the intact package of food will remain fully marketable. The food will retain any specific qualities for which express or implied claims have been made. However, beyond the date the food may still be perfectly satisfactory.
- 'Use-by date' - indicates the end of acceptable storage life. Foods that should be consumed before a certain date because of safety reasons must be marked with a 'use-by' date. Consumers need to be aware that foods marked with a use-by date should not be consumed once this date is past and it is illegal to sell them after this date.
- Bread with a shelf life of fewer than seven days may include its 'baked-on' or 'baked-for' date instead of a 'best-before' date.
Dehydrated or dried foods
Dehydrated or dried foods tend to have a long storage life measured in months or years, but they do deteriorate slowly during storage. Dried foods undergo slow chemical changes which lead to a gradual loss of quality.
Development of brown discolouration, off-flavours, and the formation of lumps in powders are the most obvious signs of quality change. High temperatures and exposure to air, particularly humid air, accelerate these changes.
The removal of water in the drying process prevents the growth of microbes, but it does not make food sterile. These foods may still contain a large number of microorganisms which can become active again in the presence of water.
Rehydrated dried foods - those to which water has been added - need to be treated as highly perishable and kept in the refrigerator. This includes desserts, dips, stocks and gravies made from dried mixes. Once these powders are mixed with moist ingredients conditions are right for the growth of bacteria.
Foods showing mould growth (hairy, fuzzy growth) should not be eaten.
Incorrectly stored dried foods are liable to absorb moisture from the atmosphere or inadvertently become wet, with the result that they may become mouldy. Foods showing mould growth (hairy, fuzzy growth) should not be eaten.
Storage times are usually indicated on the package. They apply to the unopened container stored in cool, dry conditions. Once the container has been opened the recommended storage time no longer applies.
After opening, transfer any unused portion to a screw-top jar, sealable metal container, or rigid, airtight plastic container. Large air spaces encourage deterioration so the size of the container should just take the volume of the food. Storing these foods in the refrigerator can increase storage life. This is particularly useful for moist-pack dried fruits such as apricots.
The main problem with dry foods is caused by insect infestation. Regular inspection at least once a fortnight in warm weather is recommended. Eggs laid in the food by insects before the food is packaged may survive any fumigation treatment, and hatch under warm and moist conditions.
Insects may also get into dried foods by chewing through the packaging or by entering after the package has been opened. Insect-infested food is not unsafe to eat but is usually rejected on aesthetic grounds.
The likelihood of insect attack is a strong argument against the home storage of large quantities of dried foods. Store all dried foods in airtight rigid containers with screw tops or other secure lids. This will ensure that any insects in the food do not contaminate other packages. It also makes disposal of infested material simple.