When is it safe to reheat and use leftover foods?

reheating leftover foodsFried rice syndrome is the name of a once common condition where people could become ill after eating fried rice that was left over after servings in Chinese buffets. Today, hygiene standards in Chinese restaurants are much better, but it seems food poisoning is a problem world over.

Leftover food is something we have all the time, and most people feel the shame of throwing it away. Reusing food is a nice way to save on food costs and reduce waste. If you have ever experienced food poisoning and its dangers, you understand the importance of determining and understanding when it is and when it is not acceptable to reheat leftover foods.

Close to a million people in United Kingdom suffer from food poisoning yearly. Summer barbecues and Christmas leftovers are the types of leftovers to blame most as half suffer from food poisoning resulting from their own cooking projects. Food poisoning is accompanied by vomiting, diarrhea and stomach cramps and can sometimes kill. In fact, in UK, food poisoning and its complications kill a 100 each year and the biggest culprits are very young and very old people. One in six Americans suffer food poisoning each year. So how can we stay out of the menace?

Understanding food poisoning

Food poisoning is caused by food bacteria contamination. The bacteria culprit is known as Campylobacter, and is present in 65% of chickens sold in the United Kingdom, says Food Standards Agency. Outside the packaging of supermarket chicken is 6% of the bacteria. This bacteria is bad given than lesser of them, or only 500 bacteria, are needed to make you sick compared to tens of thousands of Salmonella bacteria needed to cause an equal impact.

Bacteria may contribute to food poisoning by way of causing illnesses when they enter food or by producing toxins that act as the poison. Foods may cause poisoning because there are high amounts of bacteria in them, although some types of bacteria cause poisoning at low amounts.

Food poisoning is indicated by diarrhea, vomiting and stomach pains as the main symptoms, although nausea, headaches, fever, muscle and joint pains may occur. Long term illnesses can include kidney failure, chronic arthritis, brain and nerve damage and death. Pregnant women, older adults and persons with chronic illnesses are more susceptible to food poisoning. 

While controlling food temperature by keeping them very hot and very cold may help prevent food poisoning, in some cases it does not for some viruses and bacteria such as pathogenic E. coli. The best way to stay out of danger is to have food prevented from becoming contaminated. 


Dealing with the bacteria and food poisoning

Campylobacter can survive up to a couple of hours on a kitchen surface, so it's easy to spread around via contacts. Besides, the presence of the Salmonella bacteria in chicken presents a huge danger. The meat surface of the bird is loose enough to have as many organisms as possible inhibiting in there. The way to deal with the bacteria is through thorough heating throughout any cooking process.

However, it is necessary to understand which foods should get heated and which should not, as well as the best methods of doing it. When it comes to reheating food, many people reheat some foods several times for reuse; and while the Food Standards Agency recommend doing it once, there is no problem as long as you do it in the recommended manner. Reheating the food severally though, does not improve taste.

Particularly, the Campylobacter bacteria can spread from kitchen surfaces to food stored for future reheating and there is a danger when you do not reheat properly. This boils down depending upon the methods and processes of reheating. For instance, some methods such as the microwave achieves uneven reheating leaving cool pockets where bacteria can survive even after you take the food out for eating. It is also advisable to stir food regularly and thoroughly when reheating it. In addition, you need to discourage growth of bacteria inside the fridge by first fooling food before putting it inside the fridge - warmth encourages growth of bacteria.

According to the Food Standards Agency there are some foods which are potentially dangerous to reheat for reuse. These include cooked foods that contain meat - examples are casseroles, curries and lasagne. Foods such as patties, fish balls, stews and sauces that contain seafood and fish stock are also included. Other foods include those containing eggs, beans and nuts; protein-rich foods such as quiche, soya bean products and lentil burger; cooked rice and pasta; as well as sauces containing cream or milk.

Rice contains the Bacillus cereus bacteria that, although can die due to high amount of heat, produces heat resistant spores. If you are planning to reheat rice, do not leave it out in a warm kitchen. You can also reheat it as part of a stir fry.


When, how and which foods could be reheated

You basically can leave leftovers in a refrigerator for 3 to 4 days or freeze it for 3 to 4 months. However, frozen leftovers can lose moisture and flavor when kept for so long. To ensure safe reheating of food, all poultry foods should be reheated to a temperature of 165° F as measured with a food thermometer. Make sure to keep food in a refrigerator two hours after removal from the hot pot.

For purposes of food preservation and reheating food, bacteria lives between 40° F and 140° F and thus you should keep food hot beyond the maximum temperature limit or keep it cool in a refrigerator below the minimum temperature limit, so says the United States Department of Agriculture's Food Safety and Inspection Service.

While the key steps to handling leftovers is ensuring to cook food at the right temperatures, besides proper storage, it might still depend on the type of food to be reused/reheated. Following are the foods and temperatures at which they should be reheated before consuming their leftovers.


  • Raw beef, pork, lamb and veal steaks, chops, and roasts need to be cooked at a minimum temperature of 145 degrees before removing from heat source.
  • Ground beef, pork, lamb, and veal should be cooked at an internal temperature of 160 degree while poultry should be maintained at 165 degrees.
  • Chicken salad or a platter of deli meats are better preserved at 40 degrees or below. Make sauces, soups and gravies come to a boiling point when reheating them.
  • Chafing dishes, slow cookers, or warming trays can be used to help keep food warm enough while being served while ice, nesting dishes in bowls of ice, or use of small serving trays and replacing the servings often, can help keep food cold safely enough.

However, food left for two hours or more at room temperature or 1 hour at 90 degrees should be thrown away.

Frozen leftovers can be reheated without thawing, either in a saucepan or microwave (in the case of a soup or stew) or in the oven or microwave (for example, casseroles and combination meals).

Besides, proper storage of leftovers such as covering them with airtight packaging and sealed containers to help keep out bacteria, external odours and retain food moisture. When cooling food, cut or divide large portions into small portions.

Frozen leftovers should be reheated without thawing. Otherwise, thawed food (either by using refrigerator, cold water or the microwave oven) will take longer to reheat. Besides, refrigerator-thawed food should be used within 3 to 4 days or be refrozen. When thawed with cold water, they should be cooked before refreezing; if thawed with microwave, they should be reheated to 165 degrees before refreezing.

If more leftovers remain from the already reheated leftovers, you could still reheat them to 165 degrees and then refreeze. You can still thaw a large portion of leftover in a refrigerator, remove the unwanted portion and then refreeze the remaining thawed food without reheating.

Using a food thermometer, check temperature at various points when reheating food in a microwave for even heating. Distributing food evenly, covering to prevent moisture and adding fluids if necessary will all ensure even heating. Less dense foods such as breads, small vegetables and fruits will take less time to reheat than dense foods such as whole turkey or beef roast.


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Note: All temperatures noted above are in Fahrenheit scale, if not otherwise mentioned.


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