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Question
Fresh milk has a pH of 6. When it changes into curd (yogurt), will its pH value increase or decrease? Why?
Solution
Usually, fresh milk has a pH of 6. When fresh milk changes into curd, its pH value decreases because of an increase in the acidity of the milk. Bacteria usually change fresh milk to curd by producing lactic acid. Fresh milk that has changed into curd is sour, because its acidity has increased. Hence, the pH value of fresh milk becomes less than 6 when it changes into curd.
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