Refrigerated storage of perishable foods

Storing perishable food

Perishable food includes fruits and vegetables, fresh meat, foods purchased from chill cabinets, freshly cooked food stored to be used later. It is usually stored in the refrigerator. Some fresh fruits and vegetables, however, will store quite well out of the refrigerator as long as they are stored in a cool place.

Refrigeration can substantially reduce the rate at which food will deteriorate. Low temperatures slow down the growth of microorganisms and the rate of chemical (including enzymic) changes in food. These are two of the main causes of food spoilage.

Different parts of your refrigerator will operate at different temperatures. In older style refrigerators the upper shelves will often be slightly colder than the lower shelves.

In more modern appliances, the temperature will be relatively uniform throughout. Check your instruction booklet to find the warmest and coldest areas inside your model.

Maximising shelf life

There are simple things you can do to maximise your refrigerator's shelf life. They include:

• Check that your refrigerator is operating correctly. To do this you should use a refrigerator thermometer. These are available from some supermarkets, hardware and department stores. Your thermometer should show a temperature below 5 °C in the main section of the refrigerator.
• Avoid crowding stored products in the refrigerator; ensure good air circulation around each item. Proper storage not only keeps your food in good condition and safe from the growth of food poisoning bacteria, but saves you shopping time and money because it reduces waste.
• Some people, such as pregnant women, transplant patients and other immunocompromised persons, need to take extra care. They should consider how long chilled foods have been stored and which types they should avoid. Food Standards Australia New Zealand has produced special dietary advice on Listeria for this group.

Grocery shopping tips

To ensure the food you consume is fresh and safe to eat, below are some handy shopping tips:

• Buy only the best quality food if you plan to store it for any length of time. Bargains are not always of high quality and may have reduced shelf life. You may end up wasting money by throwing out spoiled food. If you do buy bargains, use them up quickly.
• Fresh and cured meats, fish and shellfish, dairy products and prepared foods (such as salads, quiches, filled cakes and other made up dishes) should only ever be bought from a refrigerated display. Avoid outlets which display these products at room temperature. Hard, dry cheeses (e.g. parmesan) and some salamis may be stored unrefrigerated in cool climates. However, unless you are familiar with these traditional products, refrigeration is recommended.
• Don't buy swollen chilled food packages. The contents are going off and these items should not be bought. Chilled juices, unprocessed cheeses, yoghurt and fresh pastas all contain harmless spoilage microbes when packaged. Such swelling is a sign that microbes have been allowed to grow and produce gas. This usually means the products have been stored for some time at warm temperatures or that they are near the end of their shelf life.
• Examine chilled products packed in transparent films for mould growth. Some moulds are able to grow at refrigeration temperatures.
• Take an insulated container with you when you go shopping. Always buy refrigerated food last - just before returning home. If you do not have an insulated container with you, at least make sure chilled items are wrapped in several layers of paper to minimise temperature rises during the trip home. Never leave chilled foods sitting in the car any longer than absolutely necessary.
• As soon as you arrive home, read the storage instructions on packaged foods. Then, if necessary, place the item in the refrigerator. Every minute your food spends in warm temperatures will reduce its storage life.
• Avoid overbuying. Remember chilled foods are perishable and have only a limited shelf life. The convenience and economy of quantity buying is lost if some of the food deteriorates or spoils and you have to throw it out.
• Select your retailer carefully. If you suspect food is not handled as it should be, shop elsewhere. You might also bring this to the attention of the retailer and, if necessary, the manufacturer.

Refrigerating products

Tips on how to store different types of food

Dairy products

Fresh milk, cream and some soft cheeses have only a short shelf life and lose quality rapidly if exposed to warm temperatures during storage. If you find you cannot store these products satisfactorily up to the 'best before' date, check your refrigerator temperature.

If your refrigerator temperature is below 5 °C, check how you handle the product. Does it stand around at room temperature? Do people drink directly from the carton? Do you pour milk back into the carton from a milk jug?

If you still have problems, watch how your supplier handles the product. If you suspect temperature abuse, change your supplier. Dairy products tend to pick up flavours from other foods, so keep them wrapped or covered and away from strong smelling foods.

Hard cheeses have a long storage life but may develop surface mould. If this occurs, remove the mould and about 2cm of cheese around it. Reduced salt cheeses may have a shorter shelf life than regular cheeses.

Eggs

Eggs, contrary to what many people believe, should be stored in the refrigerator. This will maintain egg quality and considerably lengthen storage life. They should preferably be stored in their cartons to reduce moisture loss through the shell.

The storage life which can be expected for eggs in the shell is determined very much by the storage temperatures during distribution. Most stores do not keep eggs under refrigeration and, depending how long the eggs have been stored at room temperature, the potential shelf life will be affected.

Raw meat, poultry and seafoods

The term 'meat' includes beef, lamb, pork, etc. These items should be stored in the coldest part of your refrigerator.

Wrapped fresh meat can be kept safely for up to three days and unwrapped fresh meat up to five days at cold temperatures, 0° to 3° C. Wrapped meat remains moist and maintains its quality but surface growth of microorganisms is encouraged and the meat becomes slimy after about three days. If you notice an off odour, the best thing to do is to throw the food out.

Unwrapped meat lasts longer than wrapped meat. When meat is stored unwrapped, the exposed surface dries out. This drying retards microbial growth but over-drying causes undesirable colour changes and loss of flavour.A compromise can be reached by storing your meat in an adequately ventilated container or loosening the wrapping around the meat so air can circulate. To ensure all surfaces are exposed to drying, place the meat on a clean stainless steel, chrome plated or plastic rack. Do not sit the meat on a plate or other solid surface, or pack it too closely. This will reduce the drying effect. Cured meat has a longer storage life. Unwrapped cured meat may last up to three weeks at 0° to 3° C.

Uncooked minced meat, liver, kidneys, poultry and seafoods need careful storage because they usually carry large numbers of spoilage microorganisms. These can grow even at refrigeration temperatures, so always store these foods in the coldest part of the refrigeration section as close as possible to 0° C. The longest recommended storage time is three days.

Before storing chilled chicken for a couple of days, it is a good idea to take off the plastic wrapping, wash the chicken thoroughly, dry it with a paper towel then store as above. Fresh whole fish should be gutted and washed if it is to be stored for more than 24 hours.

Meat designated as 'pet food' should not come into direct contact with meat for human consumption as it may have been produced under less hygienic conditions. It should be well wrapped and stored in the coldest part of the refrigerator.

Cooked meat, poultry and seafoods

Meat, poultry and seafoods must be refrigerated as soon as possible after cooking. Do not leave them on the bench top to cool before placing them in the refrigerator. The warmth of the food will encourage growth of any microbes which may get onto the meat from your hands, utensils etc. This is especially important with casserole-type dishes where food poisoning bacteria can actually survive the cooking process.

Modern refrigerators can cope with small amounts of hot foods being placed directly into them. However, to avoid excessive condensation in the refrigerator, a brief cooling period (not more than one hour) prior to refrigeration is preferred. You may wish to use a timer to remind you when the time is up.

To avoid condensation, do not cover hot meat pieces before refrigerating. Place them uncovered in the refrigerator until they are cool, then cover the container or wrap the meat tightly with cling wrap. Store cooked products above any raw meat, poultry or seafoods to avoid cross contamination from raw meat liquid or drip where this could occur. However, if the top shelves of your refrigerator are the coldest, the more perishable fresh meats should be stored there. Special care should then be taken to cover other dishes to prevent contamination.

Large amounts of food should always be divided into smaller containers before cooling. It can take many hours for the centre of a large container to cool to a temperature which will stop the growth of food poisoning bacteria. If you do not expect to eat the food within three or four days, it is best frozen immediately.

Delicatessen meats

Most delicatessen meats such as ham, corned beef, polish salami, and other luncheon meats must be stored in the fridge. They should be treated like fresh meat but they should not come into contact with fresh meat. Pâtés also fall into this group.

Some of the fermented salamis, bacon and whole hams will keep for 2-3 weeks compared to sliced luncheon meats which will keep only 4-5 days after purchase. When purchasing unpackaged pre-sliced luncheon meats, examine the products on display carefully. If there is any slime or excessive moisture, ask for slices to be freshly cut from the knob. It is a good idea to buy only small quantities of sliced luncheon meats.

Pre-packaged delicatessen items can be stored until the 'best before' date. These are often vacuum packaged and have a longer shelf life. But do buy carefully - avoiding damaged or blown packages. A slight sour smell may be noticeable as the product starts to lose quality.

There are now a series of fermented salami knobs sold which are wrapped in plastic over the casing. Make sure you read the storage instructions carefully. While the unwrapped type could be stored outside the refrigerator, these wrapped versions usually require refrigeration after the casing has been broken.

Fresh fruit and vegetables

Fruit and vegetables should be handled carefully to avoid bruising and breaking the skin. Such damage will encourage deterioration and rotting.

Most fresh produce is temperature sensitive and should be stored in the coolest part of the house when refrigerated space is not available. Some produce, particularly those from the tropics, such as pineapple and bananas, are chill sensitive and should not be stored in the refrigerator.

To reduce shrivelling or wilting due to water loss, keep leafy and root vegetables, such as silverbeet, broccoli, carrots and parsnips, in perforated plastic bags, preferably in the refrigerator.

By removing leafy tops from carrots, parsnips, turnips and beetroot, their storage life can be extended to many weeks or even several months in the refrigerator. Keep potatoes in a cool, dark, well ventilated place to avoid greening and sprouting; remove from plastic bags and place in a strong paper bag, box or in a wire or plastic bin. Sweet potatoes are cold sensitive and should not be kept in the fridge.

Cool apples, pears, stone fruits and strawberries on the refrigerator shelves, and then place into perforated plastic bags in the refrigerator. This reduces sweating (water forming inside the bag). During spring and summer the shelf life of apples at room temperature is only short. If possible remove them from refrigeration just before eating.

Keep nectarines, peaches and plums in the refrigerator, unless you want to ripen them. Pears are best kept in the refrigerator. They keep well green and hard. Store at room temperature to ripen them. Citrus fruits, cucumbers, passionfruit, capsicums and eggplant lose water easily during refrigerated storage. Waxing or wrapping in shrinkwrap helps reduce water loss.

Different varieties of a fruit often have better keeping qualities than others at a given storage temperature. For example, Fuerte avocados will not keep beyond about three weeks in the refrigerator, whereas other varieties, such as Hass, will keep up to six weeks. Also, some varieties of apples (e.g. Granny Smith and Fuji) have more than three times the storage life of others.

Tomatoes should be ripened at room temperature, away from direct sunlight. They ripen best in mildly warm temperatures. When fully ripe, especially in hot weather, they may be stored in the refrigerator for several days. However, they will gradually lose flavour and some soft areas may develop in the flesh.

Rockmelon, pineapple, paw paw, bananas, mangoes, avocados, stone fruit, tomatoes and pears need to be ripened at room temperatures. They can then be refrigerated for a short time. Fruit ripening can be accelerated by keeping unripe fruit with passionfruit and ripe apples.

To reduce mould growth in onions, whole pumpkin, marrows and squashes, store at room temperature under dry conditions, in a net or loose.

If storing large amounts of fruit, remove overripe and injured fruit regularly as these will trigger ripening and subsequent aging in the remaining fruit. Also remove any rotting fruit as infection can spread to other fruit.

The longer keeping kinds of produce can be stored for shorter periods at temperatures higher than the optimum listed in the table. Generally, however, the life of a commodity is reduced rapidly at temperatures above the optimum.

Refrigeration tips

Follow these tips to help prolong the shelf life of your food:

• Locate your refrigerator in an area with adequate air space to allow it to operate effectively. Your instruction booklet will outline the clearances required. Avoid locating the refrigerator in very hot places such as next to an oven, or clothes dryer.
• Use a refrigerator thermometer and keep the door of the refrigerator open for the shortest possible time.
• Defrost the refrigerator regularly. Ice build up reduces the operation efficiency. This does not apply to automatic defrost models. Door seals should also be checked regularly.
• Dispose of any spoiled food. Putting it in a colder part of the refrigerator will not stop it deteriorating further.
• Store food you want to keep for a long time, or items like seafood which are quite susceptible to spoilage, in the coldest part of the refrigerator. Cover all cooked foods and when practical store them on a shelf above uncooked foods. This minimises the risk of food poisoning organisms being transferred from uncooked to cooked food 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 and PVC films are not very effective barriers but they are useful in the short term and stop spillages. Closed glass or plastic containers are preferable.
• The 'best before' date is your best guide to storage life of a particular perishable food. However, it is only useful if the food has been stored correctly before you buy it. Observe the food storage practices in your favourite stores and, if you see food mishandled, shop elsewhere.