MILK AND MILK PRODUCTS

Milk nutrient-rich liquid produced by the mammary glands of mammals. It is the primary
source of nutrition for young mammals, including human infants before they are able to digest
solid food.

Milk comes in many forms and is a basic element of the diet for many people throughout the
world.

Sources of milk

i. Cows’ milk
ii. Goat’s milk
iii. Sheep’s milk
iv. Buffalo milk

However, the most common source of milk is cows’ milk as cows are widely available and also
because cows’ milk has been proven to be rich in optimal amounts of fats and protein. Milk
from cows is the most commonly used in the production of pastry products, although other
types of milk are being used more frequently due to their nutritional properties and reduced
allergenic risk.

Composition and properties of milk

Milk consists of water, sugar and fat, with a minimum fat content of 3.5%.

Milk has a slightly sweet taste and little odour.

Uses of milk and milk products in catering

i. It contributes to the nutritive value of the diet, e.g. milk shakes, flavoured milk
ii. Milk contributes to the taste and flavour of food, e.g. tea and coffee
iii. It acts as a thickening agent along with starch, e.g. White sauce or in cream soups
iv. Milk is also used in the making of desserts, e.g. ice cream, pudding
v. Curd or buttermilk is used as a leavening agent to improve the texture
vi. Curd is used as a marinating agent
vii. Curd is used as a souring agent
viii. Milk helps to increase shelf life in baked goods when used as an ingredient
ix. Milk is used in baked products to improve texture
 x. The protein in milk also gives a soft crumb structure in cakes and contributes to the
moisture, colour and flavour of a baked product.

Preservation of milk

There are various methods of preserving milk, some of which are described below:

i. Pasteurization

This is a method of milk preservation that involves the application of heat, usually
below 100 degrees Celcius at a time. In most cases, the milk is heated to between
73 and 85 degrees Celcius, then cooled quickly to 4 degrees Celcius.

Pasteurization aims to reduce the number of viable pathogens and spoilage-causing

microorganisms in order to extend the shelf life of the milk, without reducing its
quality.

The four types of milk pasteurization are:

a. Vat Pasteurisation or Low-temperature, long-time

Using this method, the milk is heated at 63 degrees Celsius for 30 minutes.

b. High-temperature, short-time

Using this method, the milk is heated at 72 degrees Celcius for 15 seconds.

c. Ultra pasteurization (UP)

Using this method, the milk is heated at 138 to 150 degrees Celcius for one to two
seconds.

d. Ultra High Temperature

Using this method, the milk is heated at 280 degrees Celcius for only two seconds.

Reasons for pasteurizing milk:

- To destroy pathogenic organisms present in milk

- To ensure the quality of milk and milk products
- To destroy the unwanted organisms
ii. Sterilization or Ultra Heat Treatment

This is a method of milk preservation which involves the application of heat, usually
more than 100 degrees Celcius at a certain time to kill almost all bacteria. The milk
is then packaged in air-tight containers either before or after heat treatment. The
sterilized milk can be kept at room temperature for a longer period.

The two methods of sterilization are as follows:

a. In-bottle or conventional method

Using this method, the milk is packed first before heat treatment and then the
packed product is heated at 105 to 110 degrees Celcius for 30 t0 45 minutes.

b. UHT/ Aseptic method

Using this method, the milk is heated at 135 to 150 degrees Celcius for 1 to 20
seconds followed by instant aseptic filling into sterile containers.

Reasons for sterilising milk:

- To ensure the quality of milk and milk products at room temperature without
refrigeration, making it safe for human consumption.
- To ensure the destruction of microorganisms

iii. Dehydration

It is the process of removal of water normally present in milk by the application of

heat under controlled conditions by evaporation. In this method, the water activity
of milk is reduced to prevent the growth of spoilage-causing microorganisms.

Reasons for dehydrating milk:

-to reduce the growth of spoilage-causing and pathogenic organisms and extend the
shelf-life of milk
 -to reduce the volume and weight of milk without compromising the nutritive value
of the milk

Quality and purchasing points for milk

i. Buy milk and milk products from trustworthy and reputable retailers and
manufacturers
ii. Always check manufacturing and expiry dates of milk and milk products
iii. Ensure that the milk is fresh by shaking it and ensuring that is does not curd
iv. Ensure that the container is airtight and that the seal is not broken
v. Ensure that the milk does not have a bad odour

Storage of milk

i. Store milk in airtight container

ii. Store milk in chilled/refrigerated conditions
iii. Store powdered milk away from heat and moist conditions.