The main ingredient in yogurt is milk. Yogurt is produced through the fermentation of milk by beneficial bacteria, primarily Lactobacillus bulgaricus and Streptococcus thermophilus. These bacteria convert lactose, the sugar found in milk, into lactic acid, giving yogurt its tangy flavor and thick texture. The fermentation process not only enhances the taste but also increases the nutritional value of yogurt by improving its digestibility and making certain nutrients more bioavailable. Yogurt may be made from various types of milk, including cow, goat, or plant-based milk alternatives, and is often enjoyed plain or flavored.