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Milk Composition & Synthesis
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Milk Composition

Water content of milk is dependent upon the synthesis of lactose. Without some water in the milk, milk would be a viscous secretion composed mostly of lipid and protein and would be extremely difficult to remove from the gland. Upon birth, the mammalian neonate is not able to seek out its own water supply and would dehydrate rapidly without the water component of milk. Water content of milk can range from a low content in marine mammals (see below) to a high content in human milk and others. Cow milk is about 87% water, so the transport of milk from the dairy farm involves hauling considerable amounts of water.

If water is added to cow milk the additional water is easily detectable by several methods. These methods are based upon changes in freezing point of the milk (cryoscopic method) or on changes in refraction of light of the whey component of milk after precipitation and removal of the casein and fat components using either acetic acid (acetic serum method) or copper sulfate (copper serum method). These methods and other standard methods of milk testing are described in the Association of Official Agricultural Chemists (AOAC), Official Laboratory Analytical Procedures, published by the National Academy of Sciences.

Key points:
  • Milk is the only source of water for the neonate
  • Water provides the aqueous medium for suspension of organic components of milk
  • Water provides medium for milk removal

Milk Composition & Synthesis