Spoilage bacteria are microorganisms too small to be seen without a microscope that cause food to deteriorate and develop unpleasant odors, tastes, and textures. These one-celled microorganisms can cause fruits and vegetables to get mushy or slimy, or meat to develop a bad odor.

There are different spoilage bacteria (see question below) and each reproduces at specific temperatures. Some can grow at the low temperatures in the refrigerator or freezer. Others grow well at room temperature and in the "Danger Zone." Bacteria will grow anywhere they have access to nutrients and water. Under the correct conditions, spoilage bacteria reproduce rapidly and the populations can grow very large. In some cases, they can double their numbers in as little as 30 minutes. The large number of microorganisms and their waste products cause the objectionable changes in odor, taste, and texture.

No, there are bacteria which are beneficial e.g. 'Dahi' we make at home has 'S.lactis' which is beneficial.
It is the Pathogenic bacteria which cause illness. They grow rapidly in the "Danger Zone"-- the temperature between 5°C and 60°C and do not generally affect the taste, smell, or apperance of food. Food that is left too long at unsafe temperature could be dangerous to eat, but smell and look just fine. E.coli O157:H7, Campylobacter, and Salmonella are examples of pathogenic bacteria.

• Mesophiles prefer moderate temperatures ranging from 5-10°C . In a favorable medium, these bacteria double their numbers in as little as 30 minutes.

• Psychrotrophs can grow at about 0°C (the freezing temperature of water), but grow best at moderate temperatures.

• Thermophiles prefer a warmer temperature. The optimum temperature for growth is usually between 55°C and 65°C. Some can grow in temperatures as low at 1.5°C or as high as 75°C to 90°C.

• Psychrophiles prefer low temperatures. They can grow at temperatures of 0° C or lower, but they can also thrive at moderate temperatures of 15°C to 20°C. They are quite common in environments where the temperature remains consistently low. They are mainly of marine origin and have little consequence in food.

Foodborne illness often presents itself as flu-like symptoms such as nausea, vomiting, diarrhea, or fever, so many people may not recognize the illness is caused by bacteria or other pathogens in food.

Thousands of types of bacteria are naturally present in our environment. Not all bacteria cause disease in humans. For example, some bacteria are used beneficially in making cheese and dahi.

Bacteria that cause disease are called pathogens. When certain pathogens enter the food supply, they can cause foodborne illness. Millions of cases of foodborne illness occur each year. Most cases of foodborne illness can be prevented. Proper cooking or processing of food destroys bacteria.

Age and physical condition place some persons at higher risk than others, no matter what type of bacteria is implicated. Very young children, pregnant women, the elderly and people with compromised immune systems are at greatest risk from any pathogen. Some persons may become ill after ingesting only a few harmful bacteria; others may remain symptom free after ingesting thousands.

There are four basic steps to follow:

Clean: Wash hands and surfaces often
Separate: Don't cross-contaminate
Cook: Cook to proper temperatures
Chill: Refrigerate promptly

Is it safe to eat lightly cooked egg dishes, or use recipes that call for raw eggs?

Today some unbroken fresh shell eggs may contain certain bacteria that can cause foodborne illness. The bacteria are Salmonella enteritidis.

Researchers say that if present, the salmonella bacteria are usually in the yolk or "yellow." But they can't rule out the bacteria being in egg whites. So everyone is advised against eating raw or undercooked egg yolks, whites or products containing them.

People with health problems, the very young, the elderly and pregnant women (the risk is to the unborn child) are particularly vulnerable to Salmonella enteritidis infections. A chronic illness weakens the immune system making the person vulnerable to foodborne illnesses.

Is it dangerous to eat raw or "rare" meat?

Yes. Raw meat may contain harmful bacteria. To be sure all bacteria are destroyed, cook meat loaf, meat balls, casseroles, and hamburgers thoroughly such that the meat turns brown in colour and reaches a core temperature of 75^oC.

Some molds are used to make certain kinds of cheeses including Roquefort, blue, Camembert etc. The mold on these cheeses is safe to eat. Mold on other types of cheeses should not be there. Discard any soft cheese showing mold.

Discard any soft fruits or vegetables, jams and jellies, bread, and baked goods that show signs of mold.

Do not eat any of the products showing signs of mold even after cutting the piece showing mold growth.

The foods in your freezer that partially or completely thaw before power is restored may be safely refrozen if they still contain ice crystals or are 5°C or below. You will have to evaluate each item separately. Generally, be very careful with meat and poultry products or any food containing milk, cream, sour cream. When in doubt, throw them out.

In general, refrigerated items should be safe as long as power is out no more than 4 hours. Discard any perishable foods that has an unusual odor, color, or texture, or feels warm to the touch.