Transcript + Milk

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Milk
Dr.Fatimah Yousef
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Composition of milk
 Milk
is a unique beverage that provides
complete protein and many of vitamins & minerals.
 The basic composition of milk regardless of the
source remains the same:
 Water 87.3% .
 Carbohydrate 4.8% .
 Protein 3.4%.
 Fat 3.7%.
 Vitamins (vitamin A,D, many of B-vitamins)
 Minerals 0.8%(especially calcium).
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Composition of milk
 Water
: The high concentration of water gives
milk a near-neutral pH of 6.6.
 Carbohydrate:
 Lactose
or milk sugar is primary carbohydrate found
in milk.
 When bacteria in milk metabolize lactose, lactic
acid is produced.
Milk
Lactose
bacteria
Milk products
Lactic acid
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Composition of Milk
 Protein:
The protein in milk is a complete protein.

Casein: The primary protein (80%) found in milk;
it can be precipitated (solidified out of solution)
with acid or certain enzymes.

Whey: The liquid portion of milk, consisting
primarily of 93% water, lactose, and whey proteins
(primarily lactalbumin and lactoglobulin). Its
concentrates are used as foaming and gelling
agents. Add the milk protein to other food
improves their texture, moisture retention, and
flavor.
Composition of Milk
+Composition of Milk
 Fat



:
It plays a major role in the flavor, mouth-feel
and stability of milk products.
Milk fat consists of triglycerides surrounded by
phospholipid-protein membranes, which allow
them to be dispersed in the fluid portion of
milk, which is primarily water.
The fat and caloric content are different in
various milk products.
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Composition of Milk
 Vitamins: Milk
contains vitamins A and D,
riboflavin (B), and tryptophan, and amino
acid important in the formation of the
vitamin niacin . It is low in vitamin C and E.
MILK exposed to ultraviolet light loses
riboflavin, so it is packaged in cardboard or
opaque plastic containers to prevent the
degradation of this vitamin by light
 vitamins
A and D found in the the milk fat of
whole milk because it is a fat soluble
vitamin
+ Composition of Milk

In reduced fat and fat free milk, however,
the vitamin A has been diminished, so
these milk are required to be fortified with
that vitamin.
 Vitamin
A fortification is also required in
dry milk and evaporated skim milk
 98
percent of milk processors add vitamin
D in reduced fat and fat free milk also it is
required in evaporated whole and fat free
milk .
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Composition of Milk
 Minerals: the major mineral in milk is calcium

Other primary minerals found in milk and milk products
include phosphorous, potassium, magnesium, sodium
chloride, and sulfur. Although milk is rich in many minerals, it
is low in iron.
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Color compounds:
 Factors
that contribute to the color of milk are:
 Fat, casein, calcium complexes,
and water
soluble riboflavin (B2).
 These compounds by interfering with light
transmission contribute to milk's color.
 Carotenoid pigments dissolved in the milk fat
influences the color of milk.
 Removing any fat eliminates a proportional
amount of carotenoid pigments and solids,
resulting in the color changing from a yellowish
white to the bluish hue seen in fat-free (nonfat) milk.
+ Purchasing Milk
Grades:
Milk is graded according to its bacterial count
Milk is an excellent growth medium for
microorganisms such as bacteria, yeast, and molds
 pasteurization : is to heat milk for a short time to
below its boiling point to kill microorganisms.
pasteurization destroys 100 percent of pathogenic
bacteria, yeasts, and molds and 95 to 99 percent of
other of the enzyme that cause the off flavor.
Pasteurization also inactivates many of the
enzymes cause off flavors of rancidity
Pasteurization temperatures and times vary but
the on commonly used is heating milk at 63
centigrade for 30 minutes or 71c for 15 sec
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Purchasing Milk
 Ultrahigh-Temperature
milk (UHT):
 A process uses higher temperatures to
destroy more bacteria than stander
pasteurization and increases the milks
shelf life. This milk is then packaged
aseptically in sterile containers and
sealed so that it
can be stored
unrefrigerated for up to 3 months.
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Types of milk
 About
half the milk produced in the market is sold
as fluid milk and cream. Much of the rest comes to
market as butter, cheese, and ice cream.
 The
available market forms of milk include:
Fresh fluid milk - whole, reduced fat, low fat, non
fat (fat-free), flavored fluid milk ex. Eggnog,
chocolate
milk.
Canned
milk,
evaporated,
sweetend condensed, dry milk. and cultured
milk such as buttermilk and yogurt.
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Types of milk
 I-
Fresh fluid milks:
 Whole milk: contain 3.25% fat and at least 8.25%
milk solids-non-fat (MSNF), It is usually fortified with
vitamin A&D.
 Reduced-fat and low-fat milk. These milks have
had some of their fat removed, fat levels are
decreased to 2 and 1 % respectively, the MSNF may
exceeds to 10 % by protein fortified, thus improve
the consistency, taste, and nutritive content. As well
as fortified with V. A &D
 Fat-free or nonfat milk (Skim): Should contain no
more than 0.5 %fat and 8.25% MSNF, fortification is
required.
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Purchasing Milk
 Reduced-lactose
milk:
any
pasteurized milk Treated will enzyme
lactase will have most of its lactose
converted to its two mono sacharids
glucose and galactose thus make it
slightly sweeter flavor. This milk is more
easily digested y people how have some
d
 Goat, sheep an other animal milks:
From various animals.
 Soy milk: A milk-like product made
from soybean.
Egree of lactose
intolerance
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Types of milk
 II-
Canned fluid milks:
 Whole milk: some ultrahigh-temperature milk is
canned.
Evaporated
milk:
60% of water evaporated.
Then homogenized, canned, and sterilized.
Sweetened
condensed milk:
50% of water evaporated.
40-45% sugar by weight.
Sterilization not needed.
Types
of
milk
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 III-
Dry milk:
 Milk is dried by either spray, foam-spray or
roller drying processes. To long shelf life.
 In spray drying, concentrated milk is sprayed into
hot air, while foam-spray drying sends a jet of hot
air into the concentrated milk. Roller drying
consists of moving pasteurized or condensed milk
through two steam-heated rollers.
 Dried milks that originally contained some fat
required to be fortified with vitamin A and D
(fortified).
 The decreased in moist and fat gives milk a long
shelf life.
 Increased the calcium and protein content.
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Types of milk
IV- Cultured milk products:
 Cultured
or fermented milk products have been
used for centuries.
 Some
cultured milk products commonly consumed
in are:
 Buttermilk
 Yogurt
 Acidophilus milk.
 Sour milk.
Types
of
milk
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 Yogurt:
 This
smooth, semisolid fermented dairy product
can be made from whole, reduced-fat or fat-free milks.
 It is produced by mixing two types of bacteria,
Lactobacillus
bulgaricus
and
Streptococcus
thermophilous, and
adding them to pasteurized,
homogenized milk.
 The whole mixture is held at a warm temperature (4246°C) to allow fermentation to develop the desired
consistency, flavor and acidity.
 During fermentation, the bacteria convert lactose to
lactic acid, increasing the acidity.
 In addition, folate levels increase as a natural byproduct of bacterial growth.
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Milk products in food preparation
1-Flavor changes:
 The
bland, slightly sweet flavor of milk comes from its
lactose, salts, sulfur compounds, and short-chain fatty
acids.
 The
percentage of fat determines the mouth-feel and
body of a particular milk.
 Exposure
to heat or sunlight, oxidation , the use of
copper equipment or utensils, and the feed ingested
by the source animal are just some of the other factors
that can influence the flavor of milk.
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Milk products in food preparation
 Off-flavor
methionine
develops
reacts
when
with
the
the
amino
acid
sunlight-sensitive
riboflavin .
 The
cooked flavor of heated milk develops in part
because heating denatures whey proteins to release
volatile sulfur compounds, which contribute to offflavors.
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Milk Products in Food Preparation
2-Coagulation and precipitation
 Some
milk proteins coagulate or precipitate
to form a solid clot, or curd, under certain
conditions. These conditions include:
 Application of heat
 Addition of:
 Acid
 Enzymes
 Polyphenolic compounds
 Salts
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Milk Products in Food Preparation
 1-Application
of heat:
 When milk is heated to near the boiling point, the
whey proteins lactalbumin and lactoglobulin
become insoluble, mesh with the milk's calcium
phosphate, and precipitate, forming a film on the
bottom and sides the pan.
 Casein not coagulate with heat unless it is boiled
for long periods of time.
 This film can scorch easily.
 Scorching can be prevented by constant stirring, slow
temperature increases , or use of a double boiler.
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Milk Products in Food Preparation
 Why
dose a skim form on the surface of heated
milk?
 This
is caused by the evaporation of water, which
is accompanied by an increased concentration of
casein, fat, and mineral salts.
 This
 To
thin skim also scorches easily.
avoid this by continual stirring during heating.
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Milk Products in Food Preparation
2-Acid:
 Adding acid to milk causes the casein in the milk
to coagulate.
 Casein precipitates when the normal 6.6 pH of fresh milk
drops below 4.6.
 Sources of acids include those from foods such as lemon,
tomato products and certain fruits, or from bacteriaproduced acids in cultured milk products.
 To prevent this by add the acid to the milk base instead of
the other way around, and avoiding high temperatures
after milk has been mixed with acid. Or thickening fluid
milk by adding starch or wheat flour.
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Milk Products in Food Preparation
3-Enzymes:
 Milk coagulates when it is combined with
certain enzymes originating from animal, plant, or
microbial sources.
 The most commonly enzyme used to coagulate
milk is rennin, which is used in the production of
cheese and ice cream.
 One of the major differences between coagulation
caused by enzymes and that initiated with acid is
that rennin-coagulated clots are rich in calcium
and have a tough, rubbery texture, unlike those
created by acid, which are less elastic and more
fragile in consistency.
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Milk Products in Food Preparation
4-Polyphenolic compounds:
 Some fruits, vegetables, tea and coffee contain
polyphenolic compounds, which when combined
with milk result in the precipitation of proteins.
5-Salts:
 Salts may cause cured for milk.
 To prevent curdling, salt or salted foods should be
added to the milk base, and high temperature
must be avoided after the combination has been
made .
Whipped Milk Products
 During
whipping, the protein in
these milk products is mechanically
stretched into thin layers that trap
air bubbles, fat particles, and
liquid.
 Whipped cream: cream expands
two to three times its volume when
whipped.
 The stability of milk foams ,
especially whipped cream, is
dependent on several factors:
 The fat content, the temperature,
and the equipment used, the age
of cream, the sugar content, and
the length of whipping time.
Whipped Milk Products
 1-Fat
content: The higher the fat content, the more
stable the whipped cream, because solid fat
particles provide rigidity to the foam.
Heavy whipping cream beats more easily than
lower-fat whipping cream, but becomes lumpy and
buttery with overbeating.
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2-Temperature: Cooling cream increases its
viscosity or firmness and its tendency to clump.
Whipped Milk Products
Whipped Milk Products
 3-The
age of cream: The older the cream , the
greater its viscosity and ability to foam.
 4-Sugar:
Sugar increases the stability of whipped
cream, but it should be added gradually, toward the
end of the whipping period.
Added earlier, it increases the whipping time and
reduces overall volume. For the best stability,
powdered sugar instead of granulated sugar should
be used, because it dissolves more readily in the cold
cream
Whipped Milk Products
 5-Whipping
time:
Physical agitation of the cream is necessary,
because it disrupts the phospholipid membranes
surrounding the fat globules, preventing them from
aggregating. Overbeating, for even a few seconds
over the peak point turns whipped cream into
butter and whey.
To make whipped cream with an electric beater, it
is best to beat on medium high and then slow to a
lower speed as soon as the cream starts to thicken.
The formation of stiff , yet moist, peaks signals the
completion of the whipping process.
The cream should be under-beaten slightly if
ingredients such as sugar are to be whipped into
the cream.
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 Whipping
evaporated milk:
The high concentration of milk solids in evaporated
milk makes it possible to whip it to three times its
volume.
But the flavor, texture, and stability are less
acceptable than the whipped cream.
Evaporated milk foams are less stable than whipped
cream foams, because of former's lowest viscosity
and lower fat content.
Adding 1½ tablespoons of sugar per cup can further
stabilize the protein and resulting foam.
Lemon juice can also be used to stabilize the foam.
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 Whipping
non-fat dry milk:
This whipped milk product is very unstable, but it
is much less expensive and lower in both calories
and fat than whipped cream.
Stability is increased by adding 1 tablespoon of
lemon juice or 2-4 tablespoons of sugar during
beating.
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Storage of Milk Products
Refrigerated
 All
fluid milk except unopened, aseptic packs of
ultrahigh-temperature
pasteurized
milk
and
certain canned milk products should be stored in
the refrigerator.
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Storage of Milk Products
Dry Storage
 Nonfat dry milk stored away from moisture and in
tightly closed containers will keep for about one
year.
 Unopened cans of evaporated and sweetened
condensed milks will keep up to a year in dry,
ventilated areas, double that if refrigerated.
 Ultrapasteurized milk can be stored unopened at
room temperature for up to three months.
 They should all be stored at or slightly below room
temperature (72°F/22°C).
 Once opened, all these milks must be refrigerated.