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Refrigerated and Frozen Food Safety
Purchasing Safe Cold Food
No swollen chilled food or meat 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 yogurt; bagged chilled chickens or parts. These items are not sterile when they are packaged. When swelling occurs it usually means they have been stored for some time at temperatures above those necessary for safe storage.
No 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.
No 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.
No refrigerated food such as casseroles, pasta etc., past its 'use-by' date - at best it could have quality defects; at worst it could cause food poisoning.
No frozen and refrigerated foods which have been stored above or outside the `load line' in the display cabinet - This is common in the waist high chest-type freezers and dairy cases! 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 2 inches below the rim of the cabinet.
No 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 The ice present in the pack is water which has been withdrawn from the food and the result usually is undesirable changes in the flavor and texture of the food.
No foods in torn packages or with imperfect seals - The food has probably deteriorated in quality.
what to examine carefully
Cheese packed in transparent films, even if bags or tubs are sealed - Look for evidence of mold growth.
Labels - They should be informative. Favor 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.
Transport while shopping
Take along an insulated container to keep items cold if there is likely to be a delay before you reach home.
Return home as soon as possible after you have finished shopping.
Place perishables in the refrigerator or freezer as soon as you get home after you have read the storage instructions.
Storing Chilled Food At home
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 ground meat, liver, kidneys, poultry and sea foods 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 ground meat thoroughly to a temperature above 75°C.
Wrapped fresh meat can be kept safely for up to three days and unwrapped fresh meat up to five days at cold temperatures 0°-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 or unwrapped meat?
Wrapped meat maintains its original high water content and quality but surface growth of microorganisms is encouraged and the meat becomes slimy after about three days and an `off' odor 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°-3°C. The meat surface dries out. This retards microbial growth but causes undesirable color changes and loss of flavor. However, this is preferable to meat going off because it is wrapped. But be sure to expose all surfaces in turn.
Safer, Longer Lasting Refrigeration
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 sea foods 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 minimizes the risk of food poisoning organisms being transferred from uncooked to cooked foods through drip.
Foods with strong odors, such as sea foods 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 odors but they are not readily available to consumers. The common cling wrap polyethylene films are not very effective for odor, 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 (0°F)almost completely stops deterioration. Thawing or even a rise in temperature without thawing stimulates chemical and microbiological activity and spoilage may occur.
Frozen foods should be brought home quickly and 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 -15°C -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 (35°F) 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.
Generally speaking, thawed food should not be refrozen. It can be stored safely in the chilling section of the refrigerator for up to 48 hours if it has been thawed properly under controlled conditions in the refrigerator.
Warning: It is bad practice to thaw meat, poultry or fish outside the refrigerator. If this has been done, never put it back into the refrigerator for use later. Cook it immediately or throw it away because there has been an opportunity for food poisoning organisms to grow.
Dehydrated or Dried Food
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. 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.
Store unopened dried foods 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. If possible store opened packages or dried fruits in the refrigerator to maintain quality for a longer period.
Inspect dried foods regularly for insect infestation as this is a constant problem.
Dips and salad dressings mixed from dehydrated ingredients should be kept in the refrigerator. Remove only as much as you expect to use, put it in a separate serving container, and don't put used dip back into the original container. 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.
Refrigerating Canned and Chilled Foods
Most canned foods have been sterilized 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 even be tasted. Any can that spews or squirts when opened may also be unsafe. Any doubtful can should be reported to the manufacturer to alert him that other cans may be in a similar condition. The contents are highly toxic; discard be burning or burying, not in trash or disposal. Throw out the contents of any can which have any unusual odor.
Any chilled products, such as canned meats and fish or fresh cut fruits in glass, which are marked `Store below 4°C (35°F)' 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.
Once a can is opened, 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. 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 pickled foods, 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.
Mark labels with date of purchase using a wax pen or indelible marker. Unopened canned foods can be stored at 21°-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.
Bacterial Action on Foods
Most cases of food poisoning are the result of eating food left to stand, cooked or uncooked, at temperatures that permit bacteria to grow.
These bacteria are present naturally in or on most foods, including as 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 contaminants to grow, we have a potentially dangerous situation. Similarly, transferring bacteria from one food to another - particularly uncooked to cooked - by careless handling may be equally dangerous.
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.
As shown in the diagram 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 cooked 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 immediately in the refrigerator to below 4°C.
Reheating should ensure that the center of the food reaches 75°C.
The same precaution should be taken with fried and barbecued meats, particularly chicken bought from delis or take-out shops. If this type of food is not to be eaten immediately, it should be kept either below 4°C or above 60°C, to avoid growth of any harmful bacteria.
Summary: Avoiding Food Poisoning in Chilled Foods
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 sea foods, meat and vegetable salads, rice salads, or 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, platters 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.
3. Kill bacteria. Reheat food to at least 75°C (175°F) to ensure that food poisoning bacteria are killed. Never eat ground meats cooked rare.