Acidity of Milk

Acidity of Milk
The determination of acidity is undoubtedly the most commonly used analytical measure on dairy technology. Since the acidity of milk is relatively constant, any increase in acidity should raise questions on the quality of the milk.

However, since it is often necessary to adjust the acidity one way or the other for processing various dairy products it is important to know which components affects acidity levels.

The pH (active acidity) of normal milk varies between 6.2 and 6.8. However, most milks have a pH between 6.4 and 6.6. Colostrum is more acid than normal milk while milks produced at the end of the lactation period, and milks produced by sick cows, generally have higher pH levels, close to those of blood.

All components capable of combining with basic ions contribute to the degree of acidity of milk. This balance between basic (sodium, potassium, magnesium, calcium and hydrogen) and acidic (phosphates, citrates, chlorides, carbonates , hydroxyls and proteins) milk components determines the degree of acidity.

These two groups of components can exists in all combinations. Also it is important to understand that these combinations can vary in their degree of ionization, dissociation constant and solubility product.

It is also important to point out that the degree of dissociation increases with neutralization or pH, and that calcium salts are less dissociated than sodium or potassium salts.

This explains why milk shows a predominance of calcium salts, which tends to combine with proteins, This is more so if the milk is more acidic.

In dairy technology, particular attention is paid to acidity fluctuations caused by processing treatments because these can affect the stability of milk components. Heating the milk produces a loss of carbon dioxide.

At high temperatures, tricalcium phosphate can precipitate and produce an increase in acidity by the dissociation of phosphate radicals.

Heat can also decompose lactose into various organic acids, or can neutralize the basic amino groups in the protein.
Acidity of Milk