Food Production

Yoghurt is made from milk using the bacterium Lactobacillus.

• Milk is first heated (pasteurised) to kill unwanted microorganisms, then cooled to about 40 °C, and a culture of Lactobacillus is added.
• The bacteria respire the milk sugar lactose anaerobically, producing lactic acid.
• The lactic acid lowers the pH of the milk. The acidity makes the milk proteins clot (coagulate), thickening the milk into yoghurt and giving it its sharp, tangy taste.
• The acidic conditions also help preserve the yoghurt by stopping the growth of many spoilage and harmful microorganisms.