Milk, this basic, nutritious and daily food, unlike what it seems, is a slightly acidic substance. Its pH is usually between values 6.5 and 6.8 on the scale and its acidity is due to a special component: lactic acid .
Milk and its composition
Milk is the secretion of the mammary glands of mammals. It is composed of different nutrients that favor the growth and development of the offspring, and that are also basic for human beings. Although both its liquid form and its derivatives are mainly consumed as food, milk has also been used since ancient times as a cosmetic for skin care due to some of its properties.
Among its most important components are:
- lactose . _ It is a unique disaccharide, present only in milk and its derivatives. It contains glucose, sucrose and amino sugars, among other substances. It can cause intolerance in some people.
- Lactic acid . Its concentration is usually 0.15-0.16%, and it is the substance that causes the acidity of milk. It is a compound that participates in different biochemical processes, one of them being lactic fermentation. It is used in nutrition as an acidity regulator in some foods and also as a beauty product to improve skin tone and texture.
- Some fats or lipids . Among them are triacylglycerides, phospholipids and free fatty acids. Cow’s milk is the richest in these components.
- casein . _ It is milk protein. It is used in the production of cheeses.
The pH of the milk
pH is a measure of the alkalinity or acidity of a homogeneous solution. It is measured with a scale that goes from 0 to 14, with 7 being the neutral point of acidity or/and alkalinity. Values above this point indicate that the solution is alkaline or basic (not acidic). If the values are less, then the compound is acidic. In the case of milk, its pH is approximately 6.5 and 6.8, therefore it is a very slightly acidic substance.
The pH of milk derivatives
The pH of dairy products is also acidic, more than that of milk itself, although it varies subtly since each milk derivative is the result of different manufacturing processes and has different chemical proportions:
- Cheeses : its pH varies between 5.1 and 5.9.
- Yogurt : pH between 4 and 5.
- Butter : pH between 6.1 and 6.4
- Milk whey : pH 4.5.
- Cream : pH 6.5.
Milk pH variation
Depending on some circumstances, the pH of milk can vary. Especially when the presence of bacteria of the Lactobacillus genus increases in it . These bacteria convert lactose into lactic acid, thus increasing its concentration, and therefore, the acidity of the milk. When the milk becomes acidic, we say that it “cut”. This can occur when consumed after several days or when exposed to heat for a long time.
In addition, the pH of the milk changes depending on whether it is whole, skimmed or powdered. On the other hand, colostrum or first breast milk is more acidic than cow’s milk.
