Milk Flashcards
What is the aim of pasteurisation?
To destroy harmful (pathogenic) bacteria without adversely affecting the quality of the milk.
How is milk heated under pasteurisation?
Pasteurisation is usually carried out by heating the milk in a heat exchanger at over 72℃ for at least 15 seconds, then cooled rapidly to below 10℃.
How do we pack pasteurised milk?
After cooling, the milk is put into stainless steel tanks and bottled as soon as possible.
How is milk heated under UHT?
The milk is heated in a heat exchanger at 132℃ for not more than one second, then rapidly cooled.
How long can unopened UHT milk be stored?
UHT milk sealed in sterile packets can last for up to 6 months if unopened.
What is the main protein found in milk?
Caseinogen.
How is dried milk preserved?
By removing water until the resulting powder contains 5% or less moisture.
What is the fat content of whole cow’s milk?
3.5%.
What is the most complete food known to exist naturally?
Milk.
What are the main milk products?
Cheese, Cream, Butter, Yoghurt.
What is the colloidal system of milk?
An oil-in-water emulsion.
How is sterilised milk different from pasteurised milk?
Sterilised milk kills harmful and souring bacteria more completely than pasteurised milk and can keep for several weeks if unopened.
How is sterilised milk produced?
Milk is homogenised, put into glass bottles, sealed, and then sterilised in an autoclave at up to 113℃ for 15-40 minutes.
What does homogenisation do to milk?
It breaks up the fat globules in the milk into very small droplets, avoiding a skin surface on the milk.
What is condensed milk made of?
Whole, partly skimmed, or skimmed milk.
How is condensed milk made?
Milk is homogenised, heated to 80℃, water is evaporated under vacuum until the milk is concentrated, then cooled and canned.
What is evaporated milk concentrated by?
Evaporated milk is twice as concentrated as fresh milk.
What is skimmed milk used for?
To reduce the energy value of the milk, often in low-fat or energy-reduced diets.
What is the fat content of semi-skimmed milk?
Less than half of whole milk.
How can pasteurised homogenised milk be stored long-term?
It can be frozen in polythene bags for up to a year.
What are dried milk substitutes made of?
Skimmed milk and non-milk fats.
What is dried artificial cream for coffee made of?
It is non-dairy, lactose-free, cholesterol-free, and gluten-free.
How are milk proteins coagulated during digestion?
Caseinogen is coagulated by rennin to form a clot.
What is the process of spray drying milk?
Milk is sprayed into a chamber with hot air to evaporate water, resulting in a powder that reconstitutes easily with water.
How does milk fat rise to the surface?
Milk fat is present as tiny globules that rise to the surface to form a cream layer.
What are the main milk proteins?
Caseinogen, lactalbumin, lactoglobulin.
How are lactalbumin and lactoglobulin affected by heat?
They coagulate and form a ‘skin’ on the surface of the milk.
What happens to caseinogen during cheese making?
It separates from calcium and phosphorus when acid is added or naturally soured by lactic acid bacteria.
How does milk fat vary in composition?
Milk fat contains both saturated and unsaturated fatty acids in varying proportions depending on the cow’s feed.
Why are dried milk with less than 26% fat not recommended for babies?
Because it lacks essential fat for their development.
