Dairy Products and Processing
The Complex Nature of Milk
• There are over 250 chemical compounds founds in milk.
• Milk is a solution that is 87 percent water . disolved in the
water the water are water soluble vitamins the milk sugar
lactose , and many trace minerals and salts.
• Finally, milk is not only a solution and a colloidal
dispersion but also an emulsion. The fat in milk is present
as small droplets or globules whose size depends on the
breed of cow producing the milk. These fat globules are
prevented from coming to gether by a thin coating of
protein emulsifiers.
COMPOSITION OF MILK
1. PROTEIN
• There are two main proteins that are dispersed as colloids in
milk. These are casein and whey .
a. Casein- about 80 percent of the milk proteins are caseins.
– can be coagulated by acids.Milk tends to curdle when mixed with
acidic foods such as tomatoes
– are quite stable in heat but can be destabalized by the enzyme
rennin which is used in the first stage in cheese making.
b. Whey- also called us serum proteins; make up the other 20 percent of
milk protein
-easily coagulated by heat.
2. FAT
• In over 400 different fatty acids founds in the lipid in cow’s milk,
only 20 individual fatty acids account for most of the fat in milk.
• Milk fat contain very little cholesterol cmpared with egg yolk.
• The fats in milk influence its flavor, texture, and price.
• The fat droplets are emulsified and suspendend throughout the
milk. However they do not stay this way but instead associate in
clusters.Eventually the clusters become large enough that their
lower density causes them to float to the top of the milk , a
process called creaming.
• To eliminate creaming, milk is homogenized .
3. SUGAR
• Lactose is the sugar that found in all varieties of milk.
• Lactose reacts with amino acids when milk is heated.
• Lactose has many functions of milk. it:
– Provides food energy
– Makes milk delicately sweet
– Lactose can be split by the enzyme lactase into the glucose (
which can be fermented) and galactose
– Adds body to milk
4. MINERAL AND VITAMINS
• Most of the minerals presents in the milk are in the form of salts.
Usually the salt make up less than 1 percent of milk. These salts
include chlorides, phosphates and citrates of potassium,
calcium, sodium , and magnessium.
• The calcium and magnesium ions and milk help the casein
micelles stable.
• Among the trace elements present in milk are cobalt, copper,
iodine, iron, magnesium, nickel, and molybdenum.
• Of the four vitamins (thiamin, niacin, and vitamin A) in milk,
riboflavin is present in the largest amount.Riboflavin is the
reason milk should be stored in cardboard or plastic containers.
MILK PROCESSING
MILK PROCESSING
• Milk should have good flavor a high nutritive value. and a satisfactory
shelf life. Shelf life is the time of a food product can be sotred before
deteriorating. Local health departments carefully regulate the processing
and sale of milk and milk products.
• Most milk sold today is pasteurized, homogenized and fortified during
processing.
• which ensures the safety of milk. Pas teurization has been used for over
100 years to kill harmful bacteria present in milk. In this process, milk is
heated to high temperatures for a short time to destroy harmful bacteria.
• Pasteurization also denatures the enzymes present in milk. In fact, one
method of testing milk to see if it has been pasteurized is to test for the
specific enzyme alkaline phosphatase. If the enzyme is present, the milk
has not been pasteurized.
MILK PROCESSING
1. Pasteurization- has been used for over 100 years to kill
harmfull bacteria. It also denatures the enzymes present in
milk.
• Phosphatase test is done to see if the milk has been
pasteurized. If alkaline phosphatase is presesent, the milk
has not been pasteurized.
• Sometimes milk is pasteurized at ultra-high temperatures
for a short period of time.This milk, called UHT milk, has
few bacteria and a long shelf life.
MILK PROCESSING
2. Homogenized- reduces the size of the fat particles
3. Fortified- milk can be fortified by exposing it ultraviolet
light.This change some of fats components in the milk to
vitamin D, Vitamin D concentrate can also be added to the
milk prior ro pasteurization.
TYPES OF MILK PRODUCTS
TYPES OF MILK PRODUCTS
• Fresh fluid milk is divided into categories according to its
fats content. The level of fat in each type of milk is set by
law.
-Skim milk has had all fat removed
-Low -fat milk contains from 0.5-2 percent milk fat.
-Whole milk contains a minimum of 3.5 percent milk fat.
TYPES OF MILK PRODUCTS
• Cream can also be divided according to the amount of fat
it contains.
-Half-and-half is 1 percent fat
-Coffee cream contains 18 percent fat
-Light whipping cream contains a minimum of 30percent fat.
-Heavy whipping cream contains a minimum of 35 percent
fat.
• Whipping cream often bears the labels UHT.
TYPES OF MILK PRODUCTS
• Evaporated milk is whole milk that has been heated at
low pressure. The result is a concentrated form of milk
that is usually homogenized, sterilized in processing, and
sealed in a tin. Carrageenin is often added to stabelized
the casien proteins.
• Condensed milk is process by removing 50 percent of
the water in the milk, adding sugar, and canning it. It is 44
percent sugar. The sugar produces a high osmotic
pressure which draws the water left in the milk away from
the nutrients needed for bacterial growth.
TYPES OF MILK PRODUCTS
• Dried milk is availabe in a powdered form. the milk used
to make dried milk is pasteurized, and then the water is
removed leaving a dry solid material.
• Fermented milks have a distinctive flavor beacuse of the
breakdown of lactose by bacterial action. (e.g buttermilk,
sour cream, yoghurt)
EXAMPLE OF MILK PRODUCT