The pH of dahi, which is another name for yogurt, is typically in the range of 3.7 to 4.5. This is significantly lower than the pH of milk, which is around 6. The lower pH of dahi is due to the formation of lactic acid during fermentation by lactic acid bacteria (LAB). These bacteria convert lactose, the sugar in milk, into lactic acid, which makes the dahi more acidic.
The exact pH of dahi can vary depending on several factors, including:
- The type of milk used: Different types of milk, such as cow's milk, goat milk, or buffalo milk, can have slightly different pH levels.
- The type of bacteria used: Different strains of LAB can produce different amounts of lactic acid.
- The fermentation time: The longer the fermentation time, the more lactic acid is produced and the lower the pH.
- The temperature of fermentation: The temperature at which the dahi is fermented can also affect the amount of lactic acid produced.
Examples:
- A study on dahi and datshi, which are fermented milk products from Bhutan, found that dahi had a pH of 3.7.
- Another study on fortified dahi found that the fortification process did not affect the pH of the dahi.
The pH of dahi is an important factor in its quality and shelf life. A lower pH indicates a more acidic dahi, which is generally considered more flavorful and has a longer shelf life.
