Chapter 9: Milk and dairy products
Natural milk
Colloidal structures, components and their functions
- Whole milk is an emulsion of fat globules in a continuous phase consisting of a colloidal
dispersion of casein micelles in a solution of globular proteins, lactose and salts
- Skimmed milk is also called plasma
o Plasma from which the casein micelles are removed = serum/whey
- Composition of the fat changes per season
o Summer cows eat grass outside, fat is more unsaturated
o Winter cows eat hay, fat is more saturated
- Lactose (carbohydrate) is the most stable compound in milk
- Casein micelles = protein present in aggregates
Fat globules
- Diameter: 0.1 5 micron
- Each fat globule has a thin layer around it prevent them from coalescing
Casein micelles
- 80% of milk proteins
- Diameter: 0.1 micron
- Micelles consists of several types of proteins aggregated together
- IEP casein pH 4.6, pH of milk pH 6.7
o Therefore, casein micelles are negatively charged and repel each other
- Outer layer of casein micelles consists of a “hairy region” formed by kappa-casein
o Hair regions prevent casein micelles in milk from coagulating together
Natural milk
Colloidal structures, components and their functions
- Whole milk is an emulsion of fat globules in a continuous phase consisting of a colloidal
dispersion of casein micelles in a solution of globular proteins, lactose and salts
- Skimmed milk is also called plasma
o Plasma from which the casein micelles are removed = serum/whey
- Composition of the fat changes per season
o Summer cows eat grass outside, fat is more unsaturated
o Winter cows eat hay, fat is more saturated
- Lactose (carbohydrate) is the most stable compound in milk
- Casein micelles = protein present in aggregates
Fat globules
- Diameter: 0.1 5 micron
- Each fat globule has a thin layer around it prevent them from coalescing
Casein micelles
- 80% of milk proteins
- Diameter: 0.1 micron
- Micelles consists of several types of proteins aggregated together
- IEP casein pH 4.6, pH of milk pH 6.7
o Therefore, casein micelles are negatively charged and repel each other
- Outer layer of casein micelles consists of a “hairy region” formed by kappa-casein
o Hair regions prevent casein micelles in milk from coagulating together
