Skim Milk Essay

CASEIN AND CASEINATE

The skim milk is a by-product obtained during manufacturing of cream. It is rich in solid-non-fat content and has high nutritional value. In dairy plants, it is mostly utilized either in standardization for the manufacturing of main products or preserved by removing moisture in spray dried form.

Casein is the principal protein found in cow milk from which it has been extracted commercially for most of the 20th century. It is responsible for the white, opaque appearance of milk in which it is combined with calcium and phosphorus as clusters of casein molecules, called micelles. The major uses of casein until the 1960s were in technical, non-food applications such as adhesives for wood, in paper coating, leather finishing

EXTRACTION OF CASEIN FROM MILK

Separation

Casein is extracted from milk using the processes outlined in Figures 2 and 3. Whole cow milk is first separated by means of centrifuges that produce cream and skim milk. Skim milk can thus be considered as the raw material from which casein products are made.

Precipitation

An important utilization of surplus skim milk is to produce casein. Casein is the principle protein milk, ranging from 24-29 g/lit of milk, accounts for 75 – 80% of the nitrogen in the skim milk. Casein exists in milk as calcium-caseinate calcium- phosphate complex. This complex substance being held in colloidal solution at neutrality – actually pH of 6.6 Casein is least soluble at a pH of 4.6 (iso - electric point of casein at 20º C), which is used as the base for production of casein.

Basic principal

The milk is acidified to the isoelectric point of casein- resulting in precipitation (coagulation) of the casein complex, (R being the casein protein).

H2N-R-COO- + H+ → +H3N-R-COO

Casein micelle acid casein

(pH = 6.6) (pH = 4.6)

Colloidal dispersion insoluble