This fact sheet helps you avoid problems when buying and storing food.
A guide to shopping
- Today most foods are purchased at supermarkets where you, the customer, can select your own purchases.
- It is a good idea to spend a little extra time examining and reading the label of each package. In this way you can often detect defects in the items before you buy, so saving time and money.
- Although the standard of food available in Australia is generally very high, problems do occur and the following hints will help you to avoid them.
Don't buy these foods
- Swollen chilled food packages—this fault is not uncommon and results from microbial action—i.e. the contents are `going off'—which produces gas and swells the container. Foods which can be affected include fruit juices, unprocessed cheeses, pasta and yoghurt. These items are not sterile when they are packaged. When spoilage occurs it usually means they have been stored for some time at temperatures above those necessary for safe storage.
- Swollen and severely dented cans—swollen cans are rare and should always be brought to the notice of the store manager because it means all is not well inside the cans. The contents of severely dented cans should never be consumed.
- Dairy products and delicatessen items kept outside a refrigerated cabinet—they should be cold at the time of purchase and the wise shopper does not buy from a store which keeps these foods at room temperature.
- Commercial refrigerated food products such as casseroles, pasta, etc. past their 'use-by' dates—at best could have quality defects; at worst could cause food poisoning.
- Frozen and refrigerated foods which have been stored outside the `load line' in the display cabinet—the load line indicates the level to which foods may be stored and remain at the correct temperature. Unfortunately this line cannot always be seen but it is usually about 5 cm below the rim of the cabinet.
- Frozen food packs containing ice crystals or packets with clumps of ice between them—both conditions indicate re-freezing and probably loss of quality. The ice present in the pack is water which has been withdrawn from the food and the result usually is undesirable changes in the flavour and texture of the food.
- Foods in torn packages or with imperfect seals—the food has probably deteriorated in quality.
Examine these foods closely
- Cheese packed in transparent films—look for evidence of mould growth.
- Labels—they should be informative. Favour those brands with labels which list storage temperatures or describe any special precautions necessary for storage. Directions for preparations are put there for a good reason and should always be followed with chilled, frozen and canned foods.
Advertising claims about the health giving properties of a food are tightly controlled by regulations. Only certain claims are permitted. The best way to ensure your family is being properly nourished is to plan meals sensibly using the Australian Dietary Guidelines and a variety of foods. Advice on this aspect of family care is freely available at Nutrition Australia.
Weekly specials in food lines can be slow moving items nearing the end of their acceptable storage life. Several weeks of storage in the home may be possible with stable items such as canned goods, but storage for many months without inspection should be avoided.
Avoid overbuying, particularly perishable foods, but also so-called long-life foods such as canned and dehydrated items. The convenience and economy of quantity buying is lost if some of the food deteriorates or spoils and you have to throw it out.
Perishable non-frozen foods
Refrigeration can substantially reduce the rate at which food will deteriorate. Low temperatures slow down the growth of micro-organisms and the rate of chemical changes in food.
The temperature in a frost-free refrigerator is fairly even. However in a moist air refrigerator the coolest part of the refrigerator is near the coils.
Thermometers made especially for refrigerators and freezers are available from some department stores and are a worthwhile investment.
Uncooked minced meat, liver, kidneys, poultry and seafoods need careful storage because they always carry large numbers of spoilage and possibly food poisoning micro-organisms. Some of these micro-organisms can grow even at refrigeration temperatures, so always store these foods in the coldest part of the refrigerator as close as possible to 0 °C.
The longest recommended storage time is three days. To kill any food poisoning bacteria which may be present, always cook minced meat thoroughly to a temperature above 75 °C.
|Food storage temperature||°C||Shelf life in the home|
|Crustaceans and molluscs||0-3||2 days|
|Minced meat and offal||0-3||2-3 days|
|Cured meat||0-3||2-3 weeks|
|Fruit juices||0-7||7-14 days|
|Cheese||0-7||variable (1-3 months)|
|Oil & Fat||2-7||variable (6 months)|
|Margarine||2-7||variable (6 months)|
|Chilled meats and meal components||0-3||no longer than 'use by' date|
Wrapped fresh meat can be kept safely for up to three days and unwrapped fresh meat up to five days at cold temperatures from 0 °C to 3 °C.
Whole red meats (e.g. leg of lamb) and cured meats have a longer storage life, and unwrapped meats last longer than wrapped meats.
Wrapped meat maintains its original high water content and quality but surface growth of micro-organisms is encouraged and the meat becomes slimy after about three days and an 'off' odour can become apparent. The safe thing to do then is to throw it out.
Unwrapped meat keeps longer—fresh meat for up to five days and cured meat for up to three weeks at 0 °C to 3 °C. The meat surface dries out. This retards microbial growth but causes undesirable colour changes and loss of flavour. However, this is preferable to meat going off because it is wrapped. But be sure to expose all surfaces in turn.
Throw out food which is going off because putting it in a colder part of the refrigerator will not stop it deteriorating further. It can taint other food.
Store food you want to keep for a long time, or items like seafoods which are quite susceptible to spoilage, in the coldest part of the refrigerator. Cover all cooked foods and store them on a shelf above uncooked goods. This minimises the risk of food poisoning organisms being transferred from uncooked to cooked foods through drip.
Foods with strong odours, such as seafoods and some cheeses, should be wrapped, and you should avoid storing them for long periods near food such as milk and cream which are susceptible to tainting.
Some flexible films are effective barriers to the transmission of odours but they are not readily available to consumers. The common cling wrap polyethylene films are not very effective, but they are useful in the short term and stop spillages. Closed glass or plastic containers are preferable.
Freezing food and holding it at a very low temperature, around -18 °C, almost completely stops deterioration. Thawing or even a rise in temperature without thawing stimulates chemical and microbiological activity and spoilage may occur.
Remember, frozen foods should be put in the freezer section of the refrigerator (or the freezer) as soon as you get home from the shop.
Long-term storage of commercially frozen foods in the home with an ordinary refrigerator is hard to justify. It is better to buy frozen foods as required because some home freezers do not hold food at a sufficiently low temperature to maintain high quality over a long period. Small quantities of bought food can, however, be held frozen for a few weeks at temperatures of between -15 °C and -12 °C without serious loss of quality.
People who freeze their own garden produce are in a somewhat different position as they have full knowledge of the storage history of the frozen product.
Cooking hints for frozen foods
Some frozen foods, particularly vegetables, should be used direct from the frozen state. Frozen vegetables usually have been blanched before freezing and need only be lightly cooked before serving.
Large cuts of frozen meat and poultry need to be thawed before use. This should be done in the refrigerator at a temperature below 4 °C to stop the growth of food poisoning bacteria. At least 24 to 48 hours in the refrigerator is usually required to thaw reasonably sized portions of foods such as whole chickens or rolled roasts. Special care is necessary when thawing and cooking turkeys or large pieces of meat—more than 3 kg.
If frozen meat has to be used at short notice it should still be thawed before cooking. This can be done under cool running water without unwrapping the meat or in a microwave oven. However, if you have to cook the meat before it has completely thawed, allow extra cooking time and ensure (by using a good meat thermometer) that the temperature in the middle of the joint has reached 71 °C.
Smaller cuts of meat such as steaks and chops can be fried or grilled direct from the frozen state.
From a safety point of view, it is fine to refreeze defrosted meat or chicken or any frozen food as long as it was defrosted for no longer than 48 hours in a fridge for running at 5°C or below.
Warning: It is bad practice to thaw meat, poultry or fish out of the refrigerator. If this has been done it should never be put back into the refrigerator for use later. If it cannot be cooked immediately it should be thrown away because there has been an opportunity for food poisoning organisms to grow.
Dehydrated or dried foods
Dehydrated foods do not readily go bad while dry, but they are deteriorating slowly all the time, particularly once the packets are open to the air.
Dehydration inhibits the growth of microbes by removing water but it does not make foods sterile and these foods may carry a high level of contaminating micro-organisms which 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.
Storage of dried foods
Store in a cool place away from obvious sources of heat such as a stove or direct sunlight. Dried foods will keep in an unopened container for about six months at 21°—24 °C.
Inspect regularly for insect infestation as this is a constant problem.
If possible store opened packages or dried fruits in the refrigerator to maintain quality for a longer period.
Savoury dips made from dehydrated ingredients should be kept in the refrigerator. Once the powder is combined with other moist ingredients conditions are right for the growth of bacteria.
Stocks, soups, sauces and gravies made from dehydrated ingredients should also be kept in the refrigerator.
Most canned foods have been sterilised during processing, which means any contaminating organisms originally present on the food have been destroyed and the cans need only be stored in a cool place. But watch for swollen or leaking cans. This indicates some failure in processing and the contents of the can should not be tasted. Any doubtful can should be reported to the manufacturer to alert them that other cans may be in a similar condition.
Any products, such as canned meats and fish, which are marked `Store below 4° C' must be stored in the refrigerator. The contents have not been fully sterilised because prolonged heating adversely affects the texture. All labels should be read carefully before the food is stored.
Adopt the same storage precautions for the contents of a can as you would for fresh food of the same kind. This is because contamination is possible as soon as the can is opened and some of the contents removed.
Throw out the contents of any can which have any unusual odour. Some foods may be stored in the can in the refrigerator and partly used cans should be covered with plastic. However, there are some preserved foods which do not store well in cans. Highly acid or salted foods such as fruit juices or tomato products do attack tinplate in the presence of air and they should be transferred to a glass or plastic container before refrigerating.
Unopened canned foods can be stored at 21 °C to 24 °C for at least 12 months.
Many canned foods will keep longer but because of uncertainty as to the true age of the food a 12-month maximum should be set.
Canned rhubarb, fruit juices, soft drinks and some baby foods are exceptions and have a maximum storage life of about six months.
Precautions during food preparation
Most cases of food poisoning are the result of eating food left to stand, cooked or uncooked, at temperatures that permit bacteria to grow, particularly those that can cause food poisoning.
Be aware that these bacteria are present naturally in or on most foods, including meat, fish, poultry, rice and vegetables. As well, many people carry potentially harmful bacteria on face, arms, hands and other parts of the body.
If, through carelessness, these organisms are transferred to a food which will support their growth such as ready-to-eat foods, and these foods are then held at a temperature warm enough to allow the organisms to grow, we have a potentially dangerous situation. Transferring bacteria from one food to another, particularly uncooked to cooked, by careless handling may be equally dangerous.
Canned rhubarb, fruit juices, soft drinks and some baby foods are exceptions and have a maximum storage life of about six months.
Safe and unsafe temperatures
The temperature at which a food is kept for any time is extremely important.
Between 4 ° and 60 °C is the temperature danger zone because this is the temperature range in which food poisoning bacteria may grow.
It is easy to reduce the risk of food poisoning by keeping the time food spends in the temperature danger zone of rapid microbial growth as short as possible.
Remember: the shorter the time foods, particularly cooked foods, spend between 4 °C and 60 °C the less are the chances of food poisoning.
If food is to be served hot after cooking it should be kept above 60 °C.
If the food is not to be eaten immediately after cooking, it should be cooled in the refrigerator to below 4 °C.
Reheating should ensure that the centre of the food reaches 75 °C.
The same precaution should be taken with fried and barbecued meats, particularly chicken bought from take-away food shops. If this type of food is not to be eaten straight away, it should be kept either below 4 °C or above 60 °C, to avoid growth of any harmful bacteria.
Avoid food poisoning
1. Control temperature
- keep food out of the temperature danger zone
- place hot food directly in the refrigerator to cool. You may be reluctant to do this but modern refrigerators can cope with the load. Provided the dish is covered you will not frost up the refrigerator
- divide large amounts into smaller portions in shallow dishes to increase the rate of cooling
- serve food to be eaten cold direct from the refrigerator. This applies particularly to seafoods, meat and vegetable salads, rice salads, desserts and cakes containing cream or imitation cream.
2. Avoid cross-contamination
- cooked meats eaten cold are a common cause of food poisoning because organisms have been transferred back to the cooked product via knives, cooking boards and hands contaminated by fresh meat
- to avoid transferring bacteria from the raw to the cooked meat, never handle cooked and uncooked meats together
- do not cut up raw and cooked foods with the same utensils or use the same boards without thoroughly washing the board and the utensils, and, of course, your hands!
- avoid excessive handling of food because bacteria are always on our bodies. Although `fingers were made before forks', suitable utensils should be used to serve food and, of course, everyone handling food should be scrupulous in their personal cleanliness.