Fresh milk has a pH of 6. When it changes into curd (yogurt) will its pH value increase or decrease? why?
The pH value of milk decreases when it changes into curd. This is because curd contains lactic acid, which is acidic in nature. Acidic substances have pH values less than 7 and that of neutral substances is equal to seven. As the pH of milk is closer to 7 (6), the pH of milk will decrease when it changes into curd.