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Shelf life is an important property of any food and is of interest to everyone in the food chain from producer to consumer.
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.
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.
No single factor may determine the shelf life of a food but the most important to be considered in shelf life studies are:
a food has undergone a commercial sterilisation process (e.g. canned
foods) or has a water activity which will not permit microbial growth
(e.g. sugar, breakfast cereals), the rate of growth of spoilage
microorganisms is likely to be the major factor determining shelf life.
This rate is determined by a number of factors including:
only is water (measured as water activity) a critical factor which
determines which, if any, microorganisms will grow in a food, many foods
are sensitive to loss or gain of water.
This in turn can be affected by the choice of packaging and in many instances will determine which packaging is used.
biscuits and savoury snacks including nuts suffer in quality as a
result of moisture gain. Some baked foods such as cakes may suffer from
Numerous possible reactions which could limit shelf life fall into this category.
The most important are oxidation, non-enzymic browning, enzymic browning and, in some cases, food and packaging interaction.
Oxidation of fats and oils leads to the development of rancidity marked by off odour and flavour.
may limit the shelf life of fats and oils but can also limit the shelf
life of many other foods containing fats and oils. Examples of foods
stored at ambient temperatures which can develop rancid off flavours are
nuts, potato crisps and biscuits.
Storage of these foods in high
oxygen atmospheres can sometimes be used to accelerate shelf life
studies but atmospheric oxygen is not the only initiator of oxidative
Many frozen foods can also have their shelf life limited by fat oxidation.
freezing arrests microbial activity, chemical reactions proceed at a
much reduced rate even at recommended storage temperatures. Examples of
frozen foods whose storage life is limited by oxidation include fish and
A number of different vitamins are sensitive to oxygen including vitamin C (ascorbic acid) and vitamin B (thiamine).
vitamins are added to fortified foods such as breakfast cereals or
sports drinks and a label declaration made, then shelf life
determinations will have to take account of any vitamin degradation
which will occur with time in addition to any other changes in quality.
Most food products rely on their particular packaging to achieve their expected shelf life.
In some circumstances the desired shelf life can be a major factor in the selection of a packaging material.
example, if for a particular market segment, the manufacturer of a
snack food packed under a modified atmosphere determines that a shelf
life of only six weeks is necessary, it may be possible for the product
to be successfully packed in a plastic with lesser barrier properties
than if the manufacturer was seeking a six month shelf life.
either case, the expected shelf life will be dependant on the integrity
of the package seal to maintain the atmosphere within the package
(beyond any expected gas transmission across the packaging film) for the
nominated shelf life.
A special case of food and packaging interaction is the use of tin plate cans with welded side seams in the canning industry.
food standards limit the concentration of certain metals in all foods
for public health reasons, there is a maximum tin content requirement
for canned foods of 250 mg/kg.
Most canned foods are now processed in lacquered cans which
substantially reduces the possibility of tin dissolution in the food.
However tin dissolution from the can is essential in some canned foods
which would otherwise be subject to discolouration.
one example of such a food. Sufficient tin is therefore left exposed in
such canned foods to ensure the expected quality of the food through its
nominated storage life without it exceeding the regulatory limit.
shelf life studies includes an assessment of the safety of the product
and this assessment will normally precede any assessment of shelf life.
is widely recognised that the most effective way to ensure food safety
is to meet the internationally recognised Hazard Analysis and Critical
Control Point (HACCP) system as adopted by the Codex Alimentarius
Commission and written into legislation in many countries including
Standard 3.2.1 of the Food Standards Code, Food Safety
Programs, which is based on the HACCP system, is being progressively
introduced into food businesses in Australia based on risk ranking by
Commonwealth and State authorities.
Standard 3.2.2, which has
been introduced throughout Australia, is titled Food Safety Practices
and General Requirements, and says in part, 'this standard sets out
specific requirements for food businesses and food handlers that, if
complied with, will ensure food does not become unsafe and unsuitable'.
The most important of these is the requirement that potentially
hazardous foods be stored below 5 °C throughout their storage life.
Correct temperature storage of chilled foods will not prevent their becoming 'unsuitable'.
Changes will occur at storage temperatures between 0 °C and 5 °C both as a result of microbial activity and chemical reaction.
These will ultimately limit the shelf life of the food and determine its best-before date.
of the wide range of foods in this category, which includes cook-chill
foods, shelf life studies and safety evaluations are usually assessed
via a challenge study rather than from accumulated knowledge as is the
case with most frozen foods.
testing is a laboratory investigation to determine what can happen to a
food product during processing and storage following inoculation with
one or more appropriate microorganisms.
A challenge study is most
frequently used to determine if pathogens will be controlled or to
estimate the time it takes for them to grow to potentially hazardous
levels, but can also be used for shelf life studies using potential
This is particularly so for acid products which receive no pasteurisation.
testing is a specialised procedure that is time consuming and expensive
but it remains an important procedure in both safety studies and shelf
Using chilled foods as an example, the aim of a shelf life test
should be to measure as far as possible the acceptable life of the
product under conditions of time and temperature likely to be
encountered during manufacture, distribution, retail storage and in the
Standard 3.2.2 requires that foods in this
category, if they can support the growth of pathogens, must be stored at
5 °C or lower.
Therefore 5 °C is the obvious baseline
temperature to use during storage trials. However the effect of
temperatures fluctuating above 5 °C needs examination as the possibility
of this occurring in actual practice is very real. It is obviously
impossible to duplicate the whole range of temperature abuse which might
occur in a product's life time.
A shelf life estimate made at,
for example, 8 °C is likely to vary significantly from an estimate made
at 5 °C and some judgment must be exercised in reconciling the two
It is essential that a cautious approach be taken until
significant real life data can be assessed. Any challenge test will only
yield a specific result for the samples under test and the conditions
under which the test was conducted.
Most shoppers look for the open date marking on foods in retail stores.
This is especially the case with short shelf life products usually those purchased from the chill cabinet.
should also check carefully the required storage conditions and
endeavour to maintain these as closely as possible on the journey home
(see our fact sheet on Handling food in the home).
The shelf life as determined by the manufacturer applies to the unopened container.
a container is opened in the home and not all of its contents used at a
single time, the excess should be returned as quickly as possible to
the manufacturer's recommended storage conditions.
manufacturers will include in their label recommendations for handling
the product after opening with regard to time and temperature.
they do not, the onus is on the consumer to handle the product
hygienically, store it at recommended temperatures and use it within a
reasonable time, certainly within the time frame specified by the
manufacturer for the unopened container.
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Last updated: Last updated: 13 April 2016
Printed from: Shelf life (http://csiroaucd1-cdc.it.csiro.au/en/Research/Health/Food-safety/Shelf-life)