TYPES OF FOOD
Milk and lactose
How pasteurization works
In the 1860s the French chemist Louis
Pasteur investigated microbial activity in
food and developed a heat treatment that
killed potentially harmful microbes without
significantly affecting flavor. This process
is applied to milk to make it safe to drink.
What’s in milk?
Milk evolved as a starter food for mammalian
infants, providing a rich, dense source of nutrients
including sugars and fats for energy, and protein,
fats, minerals, and vitamins for building and growing
bodies. Babies can survive for months on milk alone, and
adults almost can, although milk is lacking in vitamin B12,
vitamin C, fiber, and iron. The milk of different species tends
to contain the same nutrients but in different proportions.
Milk and lactose
Humans are unique among mammals in continuing to consume
milk after infancy, but our ability to cope—to a greater or lesser
degree—with the milk-sugar (lactose) opens up for us a
delicious and nutritious world of dairy products.
DOES MILK
REALLY HELP WITH
BRITTLE BONES?
Milk is rich in calcium and
phosphate—two minerals that
help to contribute to healthy
bones. For those who can’t
tolerate milk, other foods can
supply these important
minerals.
3.4% PROTEIN
3.7% FAT
4.8% LACTOSE
87.4% WATER
COOLING
HEATING
0.7% VITAMINS
AND MINERALS
Most harmful
bacteria killed by heat
C
O
W
S
’
M
I
L
K
Cooling stops the milk
from caramelizing
US_084-085_Milk.indd 84 18/01/2017 09:43
84 85
TYPES OF FOOD
Milk and lactose
What’s in milk?
Milk evolved as a starter food for mammalian
infants, providing a rich, dense source of nutrients
including sugars and fats for energy, and protein,
fats, minerals, and vitamins for building and growing
bodies. Babies can survive for months on milk alone, and
adults almost can, although milk is lacking in vitamin B12,
vitamin C, fiber, and iron. The milk of different species tends
to contain the same nutrients but in different proportions.
Diversity of dairy products
The varied composition of milk gives it great value, both as a food
source in its own right and as the base for a wonderful range of dairy
products, both fermented and unfermented. Processing is important
for milk products with medium-to-long shelf life, because even
pasteurized milk contains high levels of bacteria and will spoil quickly.
REINDEER MILK IS ONE
OF THE RICHEST MILKS
AVAILABLE: 17 PERCENT FAT
AND 11 PERCENT PROTEIN
How cream is made
Cream forms naturally in fresh, untreated
milk, because it is an emulsion that will
separate under gravity. In industrial
production, a centrifugal separator will
spin milk at high speeds in order to
separate the cream.
How condensed milk is made
Boiling milk to evaporate half its
water leaves behind condensed milk.
Its shelf life is prolonged as spoilage
microbes cannot survive with much
of the water removed. Sugar is often
added to improve taste.
How powdered milk is made
Continuing to evaporate the water
until about 90 percent is lost results
in a highly concentrated syrup,
which is then freeze-dried or
spray-dried by scattering tiny
droplets into hot air. Powdered
milk is proof against microbial
attack but can go rancid.
How ice cream is made
Milk is not simply frozen—if it were, the
fat and protein would coagulate. Instead,
it is frozen and spun at the same time in
order to force air into the mixture. This
freezes the ice crystals at a steady rate,
producing a smooth, consistent texture.
Bovine milk-drinking is a behavior that has
become widespread relatively late in human
evolution, and so the genes that make it
possible are unevenly distributed among
world populations. In most people, the level
of lactase, the enzyme that allows us to digest
lactose, decreases rapidly after infancy, so that
adults can become lactose intolerant. However,
in some parts of the world, especially in
Scandinavia, populations have evolved to
continue making lactase into adulthood.
LACTOSE TOLERANCE
SCANDINAVIA 98%
LACTOSE TOLERANT
CHINA 8%
LACTOSE TOLERANT
CENTRIFUGAL
SEPARATOR
CREAM
CONDENSED
MILK
POWDERED
MILK
ICE CREAM
SPRAY-DRIED
WATER
EVAPORATED
FREEZING
Lactose intolerantLactose tolerant
US_084-085_Milk.indd 85 23/02/2017 11:27
84 85
TYPES OF FOOD
Milk and lactose
What’s in milk?
Milk evolved as a starter food for mammalian
infants, providing a rich, dense source of nutrients
including sugars and fats for energy, and protein,
fats, minerals, and vitamins for building and growing
bodies. Babies can survive for months on milk alone, and
adults almost can, although milk is lacking in vitamin B12,
vitamin C, fiber, and iron. The milk of different species tends
to contain the same nutrients but in different proportions.
Diversity of dairy products
The varied composition of milk gives it great value, both as a food
source in its own right and as the base for a wonderful range of dairy
products, both fermented and unfermented. Processing is important
for milk products with medium-to-long shelf life, because even
pasteurized milk contains high levels of bacteria and will spoil quickly.
REINDEER MILK IS ONE
OF THE RICHEST MILKS
AVAILABLE: 17 PERCENT FAT
AND 11 PERCENT PROTEIN
How cream is made
Cream forms naturally in fresh, untreated
milk, because it is an emulsion that will
separate under gravity. In industrial
production, a centrifugal separator will
spin milk at high speeds in order to
separate the cream.
How condensed milk is made
Boiling milk to evaporate half its
water leaves behind condensed milk.
Its shelf life is prolonged as spoilage
microbes cannot survive with much
of the water removed. Sugar is often
added to improve taste.
How powdered milk is made
Continuing to evaporate the water
until about 90 percent is lost results
in a highly concentrated syrup,
which is then freeze-dried or
spray-dried by scattering tiny
droplets into hot air. Powdered
milk is proof against microbial
attack but can go rancid.
How ice cream is made
Milk is not simply frozen—if it were, the
fat and protein would coagulate. Instead,
it is frozen and spun at the same time in
order to force air into the mixture. This
freezes the ice crystals at a steady rate,
producing a smooth, consistent texture.
Bovine milk-drinking is a behavior that has
become widespread relatively late in human
evolution, and so the genes that make it
possible are unevenly distributed among
world populations. In most people, the level
of lactase, the enzyme that allows us to digest
lactose, decreases rapidly after infancy, so that
adults can become lactose intolerant. However,
in some parts of the world, especially in
Scandinavia, populations have evolved to
continue making lactase into adulthood.
LACTOSE TOLERANCE
SCANDINAVIA 98%
LACTOSE TOLERANT
CHINA 8%
LACTOSE TOLERANT
CENTRIFUGAL
SEPARATOR
CREAM
CONDENSED
MILK
POWDERED
MILK
ICE CREAM
SPRAY-DRIED
WATER
EVAPORATED
FREEZING
Lactose intolerantLactose tolerant
US_084-085_Milk.indd 85 23/02/2017 11:27
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