Dairy products Flashcards
How is butter formed?
Inversion of a cream emulsion (o/w to w/o)
Plasticity definition
Ability to retain shape under pressure
How is butter manufactured?
Milk forms cream under centrifugal separation
Cream undergoes pasteurisation, ripening, churning and draining to form butter and buttermilk
Granules are washed, salted and kneaded to form butter
How is butter a destabilised emulsion?
Air causes MFG absorption, causing MFG distribution and leaching of liquid fat. Leaching then causes clumping and air cell coalesce and collapse
How is yoghurt made?
Fermentation of milk
What is created through fermentation of milk?
3D casein structure
How is a casein structure produced?
Electrostatic and steric repulsion by trisaccharide on K-casein
Why does clumping occur during yoghurt production?
Acid causes pH to get closer to casein IEP causing aggregation
What happens to K-casein during acidification?
Causes steric repulsion on surface and therefore an aqueous phase
How is yoghurt made?
Warm milk to 50-60C
Homogenise
Heat treat
Cool to 30-45C
Inoculate with starter culture
Why is homogenisation important?
Forms stable and uniform suspension of fat
Where is homogenisation used?
Milks, yoghurt and ice-cream
What is lactose converted to during fermentation?
L (+) lactic acid, D (-) lactic acid and ATP
What does lactose fermentation cause?
pH decrease and H+ increase resulting in low electrostatic repulsion
Why does syneresis become limited?
B-lactoglobulin associates with K-casein causing slow pH decrease
How is cheese formed?
Destabilisation of casein micelles
How does acidification improve cheese?
Limits lactic acid production
Optimises coagulant activity
Increase curd strength
Promotes syneresis
Dissolution of calcium phosphate making casein susceptible to proteolysis
Role of renneting
Increase amino acids in K-casein
What can be used for renneting?
Chymosin
Pepsin
Biotechnology
What are the 2 phases of coagulation?
Enzyme action or clotting of casein micelles
How can coagulation be increased?
Increased temperature
Decreased pH
CaCl2 content
How does curd making start?
Cutting the curds to lose water and rearrange the casein network
When is salt added to cheese?
To broken curd or brine
Why is salt added?
Control microbial growth, promote syneresis, change cheese proteins and flavour
What causes ripening?
Rennet
Milk enzymes
Enzymes from starter culture
What occurs to residual lactose in cheese?
Converted to lactic acid
What is proteolysis in cheese?
Casein solubilised with amino acids is converted to amines at low pH to develop flavour and texture
Where does lipolysis occur?
Mouldy cheese as fatty acyl groups are released
