Study of yoghurt formation


A yoghurt is made by inoculation of milk with bacteria, which, between 42 and 44°C,

will grow and reject some lactic acid. This acid is responsible for the coagulation of

the casein micelles and the gelation of milk into yoghurt.

The study of this gelation process is usually done by a measurement of the pH.

However, the variation of pH is quite small (from 6.5 to 4.5) and gives little

information on the actual process.

We have followed the formation of yoghurt with a Turbiscan LAB, which exists in a

thermoregulated version, enabling to maintain the sample at the temperature

required for the growth of the bacteria. The analysis allows a close follow-up, in real

time, of the gelation process and can give additional information regarding the

measurement of the syneresis of the product and its stability with time.