Yogurt is a whitish semi-solid mass formed from the bacterial fermentation of milk. The name is derived from the Turkish word yoğurt. According to historical records, first use of yogurt was accounted by the Neolithic people of central Asia around 6000 B.C. It was not until 1919, when Isaac Carasso from Barcelona started the first industrial production of yogurt through his company now popularly known as ‘Danone.’
Two bacteria - Streptococci Thermophilus and Lactobacilli Bulgaricus are responsible for breaking down the milk sugar- lactose into lactic acid, which then acts on the milk proteins, to give yogurt its typical tart taste. During the Yogurt formation, the two bacteria coexist and support each other’s growth while acidifying milk to yogurt. During the initial phase, Streptococci Thermophilus is the most active, and when the milk acidity reaches 0.5%, Lactobacilli Bulgaricus takes over the rest of the yogurt formation and brings the total acidity to 1%.
The transformation from Milk to Yogurt happens through a two-step process: heating followed by cooling the milk and fermenting the warm milk. Heating the milk at a higher temperature concentrates the protein and gives yogurt a firm texture. On a commercial scale, heating reduced fat milk at 90 °C for 10 min and cooling it to a desired fermentation temperature of 30 °C ensures that the yogurt has the right consistency. Maintaining fermentation temperature is essential for the slow gel formation and better-set yogurt with no leaking of the whey.
For people with lactose intolerance, Yogurt is a good substitute for milk.