Milk, Fermentation, and Fermented and Nonfermented Dairy Products 159
Prior to the general use of mechanical milking devices, raw milk was the source of both human
respiratory diseases (e.g., diphtheria) as well as enteric infections (e.g., typhoid fever). When milking
a cow by hand where the milk is collected in an open pail, an infected person (or carrier) may
contaminate the milk by coughing or by hand contact. It was largely the connection between raw milk
and cases of human scarlet fever, diphtheria, and typhoid fever in the early 1900s that led the New
York City Board of Health to require milk pasteurization in 1910. The adoption of this law followed a
large outbreak of typhoid fever in New York City in the previous year, and it was traced to a common
milk supply where a chronic typhoid carrier worked.
58 The etiologic agents of all of the above-listed
diseases are destroyed by the milk pasteurization process.
In spite of the widespread use of pasteurization, milk continues to be a vehicle for some diseases. In
the case of campylobacteriosis, it is not surprising that its etiologic agent can be found in milk since
the organism exists in cow feces. In a survey of 108 samples from bulk tanks of raw milk in Wisconsin,
only 1 was positive for C. jejuni, whereas the feces of 64% of the cows in a grade A herd were C. jejuni
positive.
14 In the Netherlands, 22% of 904 cow fecal and 4.5% of 904 raw milk samples contained
C. jejuni.
6 In regard to Helicobacter pylori, it was not detected in 120 raw bovine milk samples, and
when it was added to sterile milk and refrigerated at 4
◦ C, it could not be detected after 6 days.
35 An
outbreak of 75 cases of campylobacteriosis traced to raw milk occurred in Wisconsin in 2001.
10 The
milk was from a grade A organic farm.
For the years 1973–1992, 46 outbreaks and 1,733 cases of human gastroenteritis were traced to raw
milk and reported to the Centers for Disease Control and Prevention in the United States. Of the 1,733
cases, 57% were caused by Campylobacter, 26% by Salmonella, and 2% by E. coli 0157:H7.
31 Of
the 50 states in the United States, 28 allow the sale of raw milk but <1% of the milk-borne outbreaks
during the period noted were traced to raw milk. The interstate shipment/sale of raw milk was banned
in the United States in 1987. Some of the earliest outbreaks of human listeriosis were traced to milk
(see Chapter 25). Although the outbreaks traced to dairy products may be presumed to result from the
shedding of virulent strains into milk, this is not always confirmed. In one study, L. monocytogenes
was found to be shed in milk from the left forequarter of a mastitic cow, but milk from the other
quarters was uninfected.
20 When bulk tank milk from 474 dairy herds in the Pacific northwest of the
United States were examined in 2000, 4.9% were positive for L. monocytogenes and in 2001, 7.0%
were positive with serotype 1/2a being the most common each year.
48
Yersinia enterocolitica has been found in several studies on raw milk samples. The first documented
outbreak of this organism in the United States was traced to chocolate milk, and this outbreak is further
described in Chapter 28. Twelve of 100 raw milk samples in the state of Wisconsin were positive for
Y. enterocolitica but only 1 pasteurized sample was positive.
46 Of 219 raw milk samples tested in
Brazil, 37 (16.9%) contained Listeria spp. and 32.4% were Y. enterocolitica.
74 Of 280 pasteurized
milk samples, 13.7% were positive for Yersinia spp. with 41.5% being Y. enterocolitica. The latter
species was the most common in raw milk while Y. frederiksenii at 56.1% was the most prevalent in
pasteurized milk.
74 The two largest human outbreaks of salmonellosis to occur in the United States
involved milk and ice cream, and they are described in Chapter 26.
In regard to aflatoxin M 1 in milk, a study of 290 2-liter samples of pasteurized and ultrapasteurized
milk was carried out in Mexico on the seven most widely used brands with varying fat content. Forty
percent contained AFM 1 at levels ≥0.05 ppm and 9.7% contained ≥0.5 ppm, and the range was 0–8.35
ppm in 40% of those with the lower concentration and in 10% of those with the higher concentration.
9
Milk with the highest fat content had a slightly higher probability of containing AFM 1 .
9
A study of the prevalence of E. coli 0157:H7 in fecal samples from cull cows and bulk tank milk
in east Tennessee found 8 of 415 (2%) fecal samples and 2 of 268 (0.7%) bulk tank milk samples
positive.
49 At least one large outbreak of E. coli 0157:H7 was traced to raw milk (see Chapter 27).
Prior to the general use of mechanical milking devices, raw milk was the source of both human
respiratory diseases (e.g., diphtheria) as well as enteric infections (e.g., typhoid fever). When milking
a cow by hand where the milk is collected in an open pail, an infected person (or carrier) may
contaminate the milk by coughing or by hand contact. It was largely the connection between raw milk
and cases of human scarlet fever, diphtheria, and typhoid fever in the early 1900s that led the New
York City Board of Health to require milk pasteurization in 1910. The adoption of this law followed a
large outbreak of typhoid fever in New York City in the previous year, and it was traced to a common
milk supply where a chronic typhoid carrier worked.
58 The etiologic agents of all of the above-listed
diseases are destroyed by the milk pasteurization process.
In spite of the widespread use of pasteurization, milk continues to be a vehicle for some diseases. In
the case of campylobacteriosis, it is not surprising that its etiologic agent can be found in milk since
the organism exists in cow feces. In a survey of 108 samples from bulk tanks of raw milk in Wisconsin,
only 1 was positive for C. jejuni, whereas the feces of 64% of the cows in a grade A herd were C. jejuni
positive.
14 In the Netherlands, 22% of 904 cow fecal and 4.5% of 904 raw milk samples contained
C. jejuni.
6 In regard to Helicobacter pylori, it was not detected in 120 raw bovine milk samples, and
when it was added to sterile milk and refrigerated at 4
◦ C, it could not be detected after 6 days.
35 An
outbreak of 75 cases of campylobacteriosis traced to raw milk occurred in Wisconsin in 2001.
10 The
milk was from a grade A organic farm.
For the years 1973–1992, 46 outbreaks and 1,733 cases of human gastroenteritis were traced to raw
milk and reported to the Centers for Disease Control and Prevention in the United States. Of the 1,733
cases, 57% were caused by Campylobacter, 26% by Salmonella, and 2% by E. coli 0157:H7.
31 Of
the 50 states in the United States, 28 allow the sale of raw milk but <1% of the milk-borne outbreaks
during the period noted were traced to raw milk. The interstate shipment/sale of raw milk was banned
in the United States in 1987. Some of the earliest outbreaks of human listeriosis were traced to milk
(see Chapter 25). Although the outbreaks traced to dairy products may be presumed to result from the
shedding of virulent strains into milk, this is not always confirmed. In one study, L. monocytogenes
was found to be shed in milk from the left forequarter of a mastitic cow, but milk from the other
quarters was uninfected.
20 When bulk tank milk from 474 dairy herds in the Pacific northwest of the
United States were examined in 2000, 4.9% were positive for L. monocytogenes and in 2001, 7.0%
were positive with serotype 1/2a being the most common each year.
48
Yersinia enterocolitica has been found in several studies on raw milk samples. The first documented
outbreak of this organism in the United States was traced to chocolate milk, and this outbreak is further
described in Chapter 28. Twelve of 100 raw milk samples in the state of Wisconsin were positive for
Y. enterocolitica but only 1 pasteurized sample was positive.
46 Of 219 raw milk samples tested in
Brazil, 37 (16.9%) contained Listeria spp. and 32.4% were Y. enterocolitica.
74 Of 280 pasteurized
milk samples, 13.7% were positive for Yersinia spp. with 41.5% being Y. enterocolitica. The latter
species was the most common in raw milk while Y. frederiksenii at 56.1% was the most prevalent in
pasteurized milk.
74 The two largest human outbreaks of salmonellosis to occur in the United States
involved milk and ice cream, and they are described in Chapter 26.
In regard to aflatoxin M 1 in milk, a study of 290 2-liter samples of pasteurized and ultrapasteurized
milk was carried out in Mexico on the seven most widely used brands with varying fat content. Forty
percent contained AFM 1 at levels ≥0.05 ppm and 9.7% contained ≥0.5 ppm, and the range was 0–8.35
ppm in 40% of those with the lower concentration and in 10% of those with the higher concentration.
9
Milk with the highest fat content had a slightly higher probability of containing AFM 1 .
9
A study of the prevalence of E. coli 0157:H7 in fecal samples from cull cows and bulk tank milk
in east Tennessee found 8 of 415 (2%) fecal samples and 2 of 268 (0.7%) bulk tank milk samples
positive.
49 At least one large outbreak of E. coli 0157:H7 was traced to raw milk (see Chapter 27).