Transcript MILK MILK PRODUCTS

MILK
MILK PRODUCTS
COMPOSITION OF MILK
Water - 87-88%
 Total milk solids - 12-13%
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CARBOHYDRATE – 5%
Lactose – main CHO
 Low solubility, may precipitate out as
grainy substance during heat
treatments
 Converts to lactic acid with souring or
fermentation – lactose stays in whey
 Part of milk solids non fat
 Less sweet than sucrose
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FAT
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3-4% for whole milk, varies according to state law
Primarily triglycerides, then phospholipids, sterols
Mix of unsaturated, monounsaturated,
polyunsaturated
High level of short chain – contribute to milk flavor
and low melting point of butter
Fat globules less dense than water  less stable
Milk is an emulsion
“Creaming” process – fat rises to the top
PROTEINS
CASEIN
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Primary proteingroup of similar proteins –
micellular proteins
Colloidally dispersed, poorly hydrated, calcium
sensitive, excellent emulsifiers
Can be separated by acidification to bring to
isoelectric point (4.6)
Rennin- enzyme also precipitates casein
clotting, clabbering, curdling when milk sours
WHEY
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Lactalbumin and lactoglobulin
More hydrated than casein, denatured and
precipitated by heat >600C or 1400F forms
scum on bottom of pan  scorches
Not precipitated with acid or rennet
Lactose precipitates with the whey
Enzymes – lipase, protease, alkaline
phosphatase
Casein and whey part of milk solids non fat
VITAMINS
Fat soluble - naturally in fat component
in whole milk
 High in vitamin A, some D
 Fair source of water soluble vitamins
(B), excellent riboflavin
 Small amounts of vitamin C
 Fortified with Vitamin A and D
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MINERALS
Calcium
 Phosphorus
 Magnesium
 Potassium
 Sodium
 Chloride
 Sulfur
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PIGMENTS
Fresh whole milk  ivory caused by
refraction of light in dispersed particles
 Skim milk  bluish cast
 Carotene and riboflavin yellow tinge
 Riboflavin  green tone
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FLAVOR OF MILK
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Mouthfeel due to emulsified fat, colloidally
dispersed proteins, lactose, milk salts
Fresh milk contains acetone, actealdehyde,
methyl ketones, and short chain fatty acids
to provide aroma
Normally a mild sweet flavor
Heat processing changes flavor
Affected by physical condition of cow and
composition of the feed
OFF FLAVORS
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Main cause  pasture weeds
Old or moldy feed rancid or bitter
flavors
Oxidation of fat  oxidized phospholipids
 fishy odors
Exposure to sunlight changes riboflavin
and milk proteins
CLASSIFICATION OF MILK
SOLUTION
Sugar - lactose
 Water-soluble vitamins thiamin &
riboflavin
 Mineral salts, and minerals
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COLLOIDAL DISPERSION
Casein bound to calcium phosphate in
micelle - too big to dissolve
 Whey proteins
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EMULSION
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Unstable due to large droplet phase of
fats, temporary
MILK PROCESSING
SANITATION AND QUALITY
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PHF
Grade A Pasteurized Milk Ordinance
USDA, US Public Health Service (FDA) and state
departments of agriculture regulate milk and
milk products
Voluntary
GRADES
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Grade A – available to consumer – fluid milk
Grade B & C higher bacterial count, safe,
wholesome
Grade US extra and US standard used for
dried milk
Grades based on bacterial count of fresh milk
Given on a voluntary fee for service basis
PASTEURIZATION
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Treating with heat to kill pathogens and
inactivate spoilage enzymes; some spoilage
organisms may survive so cool promptly and
hold under refrigeration
Destroys lipase which catalyzes hydrolytic
rancidity
Process is time/temperature dependent
Alkaline phosphatase - same heat
denaturation curve as milk pathogens;
presence indicates inadequate pasteurization
TIME/TEMPERATURES
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Use high temperature, short time
(H.T.S.T.) 162F, 72C for 15 seconds
Low temperature longer time
Ultra-high temperature (U.H.T.) growing, 280F for 2-4 sec. May develop
cooked flavor, use in shelf stable
products, often used with cream,
eggnog, half and half
STERILIZATION
Only occurs with ultra-high temperatures
for 2-6 seconds
 Can be aseptically packaged; no
refrigeration until opened
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HOMOGENIZATION
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Prevents creaming; maintains more uniform composition,
optional process
Mechanically reduces size, increases number of fat
globules permanently emulsifies fat globules
Characteristics:
Whiter milk
More viscous, creamy milk
More bland - fat globules smaller
Less stable to light
Increased chance of rancidity
FORTIFICATION
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Whole milk - optional addition of A & D
Lowfat milk, nonfat, low-fat chocolate - Must
be fortified for A
Addition of D optional but routinely practiced
To increase viscosity, appearance, and
nutritive value of lowfat milk, nonfat milk
solids may be added – states protein fortified
or fortified with protein
BLEACHING
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FDA - benzoyl peroxide or benzoyl
peroxide with potassium alum, calcium
sulfate, and magnesium carbonate to be
used as a bleaching agent in milk to
remove pigments such as carotenoids and
chlorophylls
Vitamin A or precursors may be destroyed
 sufficient A added into milk or curd (for
cheesemaking)
TYPES OF MILK
FLUID
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Must be free of pathogenic bacteria
Fat content and % of MSNF subject to FDA
regulations
Flavored – same nutrients as milk to which
flavor added
Certified milk – limited distribution due to
cost, sanitary standards very high
Eggnog- mixture of dairy ingredients (cream,
milk) egg yolk containing ingredients,
nutritive carbohydrate sweeteners.
OTHER FLUID MILK
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Canned whole milk – homogenized, sterilized, canned
aseptically
Frozen whole milk – homogenized, pasteurized, fat
separates when thawed, protein denatured by freezing
Skim or nonfat – as much fat as possible removed,
minimum of MSNF, fortified with vitamin A. Optional:
vitamin D, emulsifiers, stabilizers
Low-fat milk – some fat removed, named according to fat
remaining, minimum MSNF, fortified with vit. A. Optional:
Vit. D, emulsifiers, stabilizers
Labeled with protein fortified if MSNF >10%
CONCENTRATED MILKS
EVAPORATED MILK
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Concentrated through process of evaporation
Evaporated in a vacuum chamber
Whole or nonfat – 60% of H2O removed
Homogenized, fortified, canned, sterilized
Increasingly less stable with progression of
concentration and heat  may coagulate 
prevent by forewarming
Maillard reaction  light tan color
Reconstitute 1:1 ratio
CONDENSED MILK
Similar in content and use to
evaporated milk
 NOT sterilized
 Perishable at temperatures above 450F
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SWEETENED CONDENSED
MILK
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Concentrated whole or nonfat milk
60% of H2O removed
Sweetened with sucrose or dextrose prior to
concentration
40-45% sugar level, may cause grittiness
Pasteurized, not sterilized due to high
concentration of sugar
Used in pie filling – thickening occurs
because concentrated proteins coagulate
from the effect of added acid
DRIED MILK
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Processed from whole or nonfat milk (more
common)
Condensed 2/3 of H2O removed
Sprayed into heated vacuum chamber  less
than 5% moisture level
Most nonfat fortified
“Instant” or “agglomerated” – some moisture
added back pourable, dispersible, in cold
H2O
May also dry buttermilk, whey
CULTURED AND FERMENTED
MILK AND MILK PRODUCTS
CULTURED/FERMENTED
Cultured products fermented by
addition of bacterial culturesStreptococci and Lactobacilli
 Ferment lactose  lactic acid; create
low pH to coagulate casein
 Acidified products – souring milk with
acid, with or without microorganisms
 Cultured and acidified products contain
different amounts of lactic acid 
different flavors
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BUTTERMILK
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Traditionally liquid left after churning butter,
differs from nonfat milk due to content of
phospholipids and proteins from fat globule,
NFDM solids added
Cultured buttermilk – pasteurized lowfat or
nonfat milk with Lactobacilli and Streptococci
added
Acidified buttermilk – lactic acid producing
bacteria not compulsory
Smooth cultured flavor, high acid content
useful in cooking
SOUR CREAM
Traditionally heavy cream soured
 Pasteurized, homogenized fresh light
cream
 Coagulated similar to buttermilk
 Flavors, stabilizers added
 Proteolytic bacterial enzyme activity
may cause bitter flavor after 3-4 weeks
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YOGURT
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Culture pasteurized dairy product with
lactobacillus bulgaricus and streptococcus
thermophilis
National Yogurt Association seal for live and
active bacteria; at least 100 million
bacteria/gram at time of manufacture
Yogurt with viable strains of bacteria eaten in
sufficient quantities some will survive
passage through stomach and release lactase
in the intestine
OTHER PRODUCTS
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Acidophilus milk - pasteurized low-fat or nonfat milk
with Lactobacillus Acidophilus added, Bacteria can
live in intestine and produce number of B vitamins
Reduced Lactose milk - pasteurized milk treated with
lactase
sweeter than regular milk
Kefir– fermented dairy products, kefir grain yields
bacteria added to milk
Koumiss – milk heated before fermentation
Ferments to yield soft curd with yeasty sour curd with
mild alcoholic flavor
MILK SUBSTITUTES
Imitation milk – combination of several
nondairy ingredients; nutritionally
inferior
 Substitute milk – nutritionally
equivalent; reduced calories or fat,
usually milk derivatives ( casein, casein
salts, whey)
 Filled milk – substitute milk with
milkfat replaced with vegetable oil
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CREAMS
DESCRIPTION
High fat component separated from
milk
 Federal standards must have at least
18% milkfat
 Yellow, fat-soluble pigments visible
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TYPES
Light coffee cream – 18-30%
 Light whipping cream – 30-36%
 Heavy cream – 36% butterfat,
minimum
 Half and half – cream diluted with
nonfat milk 10.5%
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PRINCIPLES OF USING MILK
AND MILK PRODUCTS
EFFECTS OF HEAT
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Prolonged heating adversely affects:
Flavor – dependent on length of time of
heating and temperature reached
Due to production of sulfur compounds from
denaturation of whey proteins
Due to caramelized flavor from Maillard
reaction
Odor
Cooking properties
HEAT AND MILK PROTEINS
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Heated milk forms precipitate on bottom and
sides of pan – coagulated whey proteins
Precipitated proteins tend to scorch
One whey protein component produces a low
volume in yeast breads made with unheated
milk- scalded milk greater volume in yeast
breads
Heated in uncovered pan forms “skin” –
coagulated proteins, fat, minerals because milk
drying out on top
Prevents steam from escaping  boil over
HEAT AND MILK PROTEINS
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Casein changes little under normal heating
May not take place until milk has been boiled
for 14 hours
Temperatures above boiling  cleavage of
peptide and phosphate bonds
In concentrated milks coagulation greater
due to protein concentration
Unstable emulsion like soured milks
accelerate coagulation with heat
HEAT AND MILK MINERALS
Decreases dispersion of calcium
phosphate
 Precipitates and becomes
enmeshed in whey proteins on
bottom of pan
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EFFECT OF ACID
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Normal pH = 6.5-6.7
Add acid  pH decreases
Below 5.1 casein destabilizes
At pH 4.5 casein salts formed  milk curdles
Coagulum traps whey which is released when curd is cut,
stirred, or heated
Curd is soft, fragile
Cheese from acid coagulation is low in calcium compared to
whey
Cream of tomato soup – separates milk proteins
Acids in fruits curdle milk in smoothies
Add lemon juice to sauce at end of cooking
EFFECT OF ENZYMES
Coagulate proteins
 Clabbered by rennin – stomach of milkfed calves – extract is rennet, now use
pepsin from hog stomachs
 Genetically engineered rennet from
genetically modified Aspergillus mold
 Clots are tough, rubbery, contain most of
calcium
 Add to warm milk for optimal activity
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EFFECT OF ALKALI
Baking soda, for example
 Stabilizes colloidal dispersions
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EFFECT OF POLYPHENOLIC COMPOUNDS
Tannins
 Astringent compounds found in
fruit, vegetables, plant foods
 Produce curdling especially if
soured or destabilized by heat
 Potatoes cause curdling in
scalloped dishes
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EFFECT OF SALT
In high concentration will
destabilize a gel
 Influences coagulation of casein
 Ham added to milk-based dish
high sodium content curdles
surrounding liquid
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