5.7 understand the role of bacteria (Lactobacillus) in the production of yoghurt

1. Milk is pasteurized at 85-95 Celcius for 15-30 minutes to kill any natural bacteria it contains.
2. Milk is homogenized to dispense fat molecules/globules.
3. Milk is then cooled at 40-45 Celcius and added with Lactobacillus and streptococcus.
4. These bacteria produce lactic acid and digest milk proteins. The culture is kept at this temperature for several hours while pH falls to 4. This drop in pH will cause the mixture to thicken as milk proteins will denature due to the drop in pH and turn semi-solid.
5. When the fermentation process is finished, the yogurt is stirred and cooled to 5 Celcius. Flavours, colourings are added before packaging for sale.