Bài luyện nghe số 4 chuyên ngành Công nghệ sinh học

Curing Meat
By Mario Ritter
Broadcast: Tuesday, March 04, 2003
This is the VOA Special English Agriculture Report.
People discovered long ago how to dry meat to keep it safe for a long time. This process called curing
interferes ( to prevent something from continuing or developing successfully ) 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 that 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 (TRICK-a-NELL-o-sis). 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.