Yogurt is made through fermentation when bacteria convert lactose, the sugar in milk, into lactic acid.
Here's a breakdown of the process:
-
Introduction of Bacteria: Specific bacteria cultures, typically Streptococcus thermophilus and Lactobacillus bulgaricus, are introduced to milk. These are often referred to as "yogurt cultures."
-
Lactose Fermentation: These bacteria consume the lactose (milk sugar) and produce lactic acid as a byproduct.
-
Acidification and Coagulation: The increasing levels of lactic acid lower the pH of the milk, making it more acidic. This acidity causes the milk proteins (primarily casein) to denature and coagulate, resulting in the thickening of the milk and the formation of the yogurt's characteristic texture.
-
Flavor Development: Besides thickening, the fermentation process also contributes to the flavor of yogurt. The lactic acid imparts a tangy taste, and other byproducts of bacterial metabolism contribute to the overall flavor profile.
In summary, the fermentation process, driven by specific bacteria, transforms milk into yogurt by converting lactose to lactic acid, which causes the milk proteins to coagulate and develop the characteristic flavor and texture.
