Milk Pasteurization

موضوع: Milk Pasteurization الأربعاء سبتمبر 02, 2009 10:45 pm

[size=29]Furthering Families
[/size][size=29]Milk pasteurization
[/size][size=25]Guarding against disease
[/size]Milk, a natural liquid food, is one of our most nutritionally complete foods, adding
high-quality protein, fat, milk sugar, essential minerals, and vitamins to our diet.
However, milk contains bacteria that––when improperly handled––may create
conditions where bacteria can multiply. Most of the bacteria in fresh milk from a
healthy animal are either harmless or beneficial. But, rapid changes in the health of an
animal, or the milk handler, or contaminants from polluted water, dirt, manure,
vermin, air, cuts, and wounds can make raw milk potentially dangerous.
How do microorganisms enter the milk supply?
Our environment contains an abundance of microorganisms that find their way to the
hair, udder, and teats of dairy cows and can move up the teat canal. Some of these
germs cause an inflammatory disease of the udder known as mastitis while others
enter the milk without causing any disease symptoms in the animal. In addition,
organisms can enter the milk supply during the milking process when equipment used
in milking, transporting, and storing the raw milk is not properly cleaned and sanitized.
All milk and milk products have the potential to transmit pathogenic (disease- causing)
organisms to humans. The nutritional components that make milk and milk products
an important part of the human diet also support the growth of the organisms.
Drinking raw milk causes foodborne illness, and dairy producers selling or giving raw

milk to friends and relatives are putting them at risk.What are common pathogens in milk?
Illnesses from contaminated milk and milk products have occurred worldwide since
cows have been milked. In the 1900s it was discovered that milk can transmit
tuberculosis, brucellosis, diphtheria, scarlet fever, and Q-fever (a mild disease
characterized by high fever, chills, and muscular pains) to humans. Fortunately, the
threat of these diseases and the incidence of outbreaks involving milk and milk
products has been greatly reduced over the decades due to improved sanitary milk
production practices and pasteurization.
• Salmonella. Salmonellosis is the most common disease transmitted in raw milk.
This organism is shed in the feces of cattle and picked up on the animals’ hair or
teats. Many strains of Salmonella can cause foodborne illness in humans, and all
strains exhibit the same symptoms such as gastroenteritis (vomiting and diarrhea).
Pasteurization destroys the Salmonella organism, and although pasteurized milk,
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powdered milk, and cheese have been implicated
in salmonellosis outbreaks, in these cases, the
pasteurized milk was contaminated during further

processing.Listeria monocytogenes. This widespread
organism is found principally in soil.
Listeriosis in humans may cause serious illness,
and is especially dangerous to pregnant
women, causing stillbirths or infant death soon
after birth. Pasteurization inactivates Listeria
monocytogenes.
• Yersinia enterocolitica. This common
organism has been found in many foods of
animal origin including milk, cheese, and red.
Yersinia, found in streams, lakes, and wells,
spreads from the water to warm-blooded
animals. The most common symptom of
yersinosis is gastroenteritis and mimics the
symptoms of appendicitis. Yersinia
enterocolitica is destroyed by pasteurization.
• Campylobacter jejuni. This organism,
isolated in raw milk and meat, can cause
mastitis in dairy cattle. It has also been isolated
in the feces of many species including dogs,
cats, rodents, cattle, sheep, swine, and poultry.
Symptoms include vomiting, cramps, bloody
diarrhea, mild enteritis, or severe enterocolitis.
Individuals who have recovered from the
disease may suffer a relapse. Campylobacter
jejuni is destroyed by pasteurization.
• Staphylococcus aureus is a common cause
of mastitis in dairy cattle and can enter the milk

supply from sores on the teats of cows or fromthe hands and nasal discharges of dairy farmers
and workers. The Staphylococcus organism
produces an enterotoxin (toxins causing
vomiting and diarrhea) in raw milk when it is
held at temperatures above 50 degrees
Fahrenheit. Sufficient amounts of enterotoxin
in foods can cause illness. The incidence of
staphylococcal intoxication has been greatly

reduced by pasteurization.• Escherichia coli 0157: H7. Recent
studies show that young dairy cattle are host
to E-coli and fecal contamination is a likely
source of E-coli in raw milk. It can cause
hemorrhagic colitis and hemolytic uremic
syndrome in humans. Milk should be stored
at temperatures below 40 degrees
Fahrenheit to inhibit the growth of
Escherichia coli 0157: H7. Temperature
abuse during holding and shipping can cause
significant growth of the organism.

Pasteurization destroys this organism.

[size=25]Pasteurization and handling requirements
[/size]Pasteurization, named for Louis Pasteur who developed the process for other foods, is
a moderate but exact heat treatment of milk. Pasteurization kills bacteria that produce
disease and retards spoilage in milk.
What is pasteurization?
Pasteurization destroys most disease producing organisms and limits fermentation in
milk, beer, and other liquids by partial or complete sterilization. The pasteurization
process heats milk to 161 degrees Fahrenheit (63 degrees centigrade) for 15 seconds,
inactivating or killing organisms that grow rapidly in milk. Pasteurization does not
destroy organisms that grow slowly or produce spores.
While pasteurization destroys many microorganisms in milk, improper handling after
pasteurization can recontaminate milk. Many dairy farms use a home-pasteurizing
machine to pasteurize small amounts of milk for personal use. Raw milk can also be
pasteurized on the stovetop. Microwaving raw milk is not an effective means of
pasteurization because of uneven heat distribution. For more information on
purchasing and caring for home pasteurization machines, contact your county
Extension agent.
Ultra-high temperature (UHT) processing destroys organisms more effectively and the
milk is essentially sterilized and can be stored at room temperature for up to 8 weeks

without any change in flavor.
What are the requirements for safe handling of milk?
The requirements for proper pasteurization and handling of milk are:
• A potable water supply and proper dispensing system must be available to
avoid contamination. A pure hot and cold water supply for the animals’
health, and for proper cleaning of the animals, milk handlers and utensils.
Regular inspection and maintenance of the system is necessary.
• Clean and healthy animals, clean hands, and clean utensils are essential.
The animals’ hair should be clipped regularly around the flanks and udder to
keep it from collecting dirt. Milkers should walk their hands and the udder with
clean water or use an approved germicidal solution before milking. Milk from

diseased animals or those under antibiotic treatment may not be used. Allequipment and utensils should be cleaned
immediately after use. Stainless steel utensils
are preferred since they are durable and easy to

clean.

• Rapid cooling, cold storage, proper
pasteurization, and clean cold storage of
pasteurized are necessary for the prevention
of foodborne illness. Milk must be promptly
cooled to 40°F (4°C) or less and stored in a
closed container before and after pasteurization
to maintain the quality and flavor of the milk.
Care should be taken not to transfer barnyard dirt from
the bottom or sides of the storage container to the
countertop or to utensils in the pasteurization and
storage areas.
Do not mix fresh milk with previously cooked milk
unless you plan to pasteurize the entire batch
immediately.
How do I pasteurize milk?
Milk must be heated, with agitation, in such a way that
every particle of the milk, including the foam, receives
a minimum heat treatment of 150°F (66°C)
continuously for 30 minutes or 161°F (72°C) for 15
seconds. The temperature should be monitored with
an accurate metal or protected glass thermometer.

Commercial operations commonly use a hightemperature,hightemperature,
short-time process in which the milk is
heated to 170°F (77°C) for 15 seconds and then
cooled immediately to below 40°F (4°C) to increase
storage life without any noticeable flavor change in
the milk.
Pasteurization of fluid milk has very specific
requirements for time and temperature as listed in

the chart.

Temperature-Time Pasteurization
Requirements for Fluid Milk
Temperature Time
• 150°F (66°C) 30 minutes
(vat pasteurization)
• 161°F (72°C) 15 seconds
(high temperature, shorttime
pasteurization)
• 191°F (89°C) 1 second

• 212°F (100°C) 0.01 second
[size=7]References
Namminga, Kelly, (1999), “Health Risks of Drinking Raw
(Unpasteurized) Milk,” [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]
South Dakota State University, Brookings, SD (reviewed by E. Kim
Cassel, SDSU Extension Dairy Specialist).
Smith, P. W., (August 1981), “Milk Pasteurization” [/size][size=7]Fact Sheet Number
57[/size][size=7], U.S. Department of Agriculture Research Service, Washington,
D.C.
Compiled by [/size][size=7]Cindy Brock[/size][size=7], Extension Educator, Food Safety Area of
Expertise Team, Cheboygan, Montmorency, and Presque Isle
Counties, Michigan State University Extension
Reviewed by [/size][size=7]John Partridge[/size][size=7], Ph.D., Professor, Food Science and

Human Nutrition, Michigan State University[/size]

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موضوع: رد: Milk Pasteurization الخميس سبتمبر 03, 2009 3:03 am

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موضوع: رد: Milk Pasteurization الخميس سبتمبر 03, 2009 4:19 am

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