People discovered long ago how to dry meat to keep it safe for a long time. This process called curing interferes with the growth of bacteria. Curing meat is a traditional method used by many cultures. It can be done with some common chemicals. The most common is sodium chloride -- salt.

Some very harmful bacteria, like salmonella, can be controlled with low levels of salt. But other kinds of bacteria can require high levels of salt or high drying temperatures to control.

The simplest way to cure meat is to put it into a lot of rough salt for several days. This method provided meat for the sailors who came to the New World with Christopher Columbus.

Another method requires meat to be kept in a salty liquid, called brine, for several days. The meat is then hung out to dry. Traditionally, this kind of curing is done during cold winter months. Meat begins to break down at temperatures warmer than five degrees Celsius.

Today, the meat processing industry speeds up the curing process. Curing factories inject salty liquid directly into the meat. Then hot air dries the meat quickly at temperatures of thirty-five to forty degrees.

Cured meat becomes gray. But people discovered that another common chemical, nitrate, can prevent this. Nitrate is added to most cured meats. However, the United States Food and Drug Administration limits the amounts. That is because nitrates can react with proteins to form chemicals that cause cancer in laboratory animals.

Curing does not destroy all the organisms known to infect uncooked meat. The Trichinella worm, for example, causes the infection trichinellosis. Scientists at the American Centers for Disease Control and Prevention say curing does not completely kill the trichinella worm. They say it is killed by cooking meat to seventy-seven degrees Celsius.

Curing is an important method to preserve meat. Cooking cured meat can provide extra safety to prevent the possibility of infection.

In any case, cured meats may contain a lot of salt. Doctors advise people with high blood pressure and heart disease to limit how much salt they eat.

This VOA Special English Agriculture Report was written by Mario Ritter.