Presentation on theme: "Isolation of Casein from Milk"— Presentation transcript:
1 Isolation of Casein from Milk ■ Kinds of proteins in milk:CaseinLactalbuminLactoglobulinThey are complete proteins.
2 Molecular surface model of CaseinThe main protein in milkPresent at a concentration of about 35g/l.It is a phosphoprotein.Not a single compound, it is a heterogeneous mixture of αS1 , αS2 , β, κ.Casein exists in milk as the calcium salt, calcium caseinate.Molecular surface model ofK-Casein.
3 * Principle ■ The isoelectric point of a protein (I.E.P.) : is the PH at which the molecule is electrically neutral (net charge is zero).When a protein is charged e.g. with a –ve charge, the –ve molecules repel each other and thus remain in the solution and do not precipitate.When a protein is neutral at the I.E.P. they tend to precipitate due to the absence of the repelling forces and, the high molecular weight of protein.Most proteins show minimum solubility at their isoelectric pointPH of milk is (its isoelectric point).Casein is also insoluble in ethanol and this property is used to remove unwanted fat from the preparation.Milk is present at a high PH than the isoelectric point of casein
4 Measure the pH of the milk 6030154551020253540505560301545510202535405055Add 2 ml of CH3COONaAdd 2 ml of CH3COOH 10%Measure the pH of the milk40 ºC25 ºC30 mlDistilled Water30 mlMilkpH=4.5
5 Shake well ph.ph. 10 ml 0.1N KOH 80 ml D.w. 10 ml H2O Precipitate 10 ml 95% alcohol10 ml ether10 mlether-alcohol mix.10 ml H2O
6 0.1N HClVBVTBlank10 ml 0.1N KOH80 ml D.W.3drops ph.ph.
7 * Calculations 1L (1 N) KOH = Mwt of casein 1 ml (0.1N) KOH = Mwt. Of Casein10×10001ml (0.1N) KOH = g casein = 1 ml HClVolume of Casine = VB - VT(VB-VT) x = ? g casein/30ml milkY = ? g casine %Y = (VB-VT) x x 10030Samar A. Damiati