The milk from the animal immediately starts to show an acidic reaction. This is called natural acidity. This initial acidity does not last for long. During milking and during the milking period, a large number of microorganisms start to infect the milk depending on various conditions. With this activity of microorganisms, acidity level in milk starts to increase.

The acidity of the milk is made to determine whether the milk is fresh and normal, whether it will withstand heat during processing, whether a neutralizing agent is added, or whether the milk complies with the current legal regulations, standards and Turkish Food Codex.

Many tests are performed in dairy farms. Test studies, such as, for example, titration acidity, alcohol test or boiling test, are intended to determine the stability of milk, or to determine the increase in acidity in milk. The acidity level of the milk is directly related to its hygiene quality. The degree of acidity supports the decision on which food products are suitable for milk. Acidity status is an indicator of quality in some dairy products and helps to control production in some dairy products.

Two different methods are used in the determination of acidity by milk titration method. The first method is to determine the acidity percentage in lactic acid. The second method is to calculate the Soxhlet-Henkel (SH) degree.

According to the Turkish Food Codex Communiqué on Raw Milk and Heat Treated Drinking Milk, the acidity of raw milk should be between the following values ​​in terms of milk acid:

• Cow's milk percent 0,135 - 0,20
• Sheep's milk percent 0,160 - 0,35
• Goat milk percent 0,150 - 0,28
• Buffalo milk percent 0,140 - 0,22

In the authorized laboratories, lactic acid determination in milk is carried out using High Performance Liquid Chromatography (HPLC) device within the scope of chemical tests. These studies comply with the standards published by national and international organizations.