Chapter 2: Problem 11

Fresh milk has a pH of 6 . How do you think the pH will change as it turns into curd? Explain your answer.

Short Answer

Expert verified

The pH will decrease, making the curd more acidic.

Step by step solution

Understanding pH

pH is a measure of how acidic or basic a substance is. A pH less than 7 is acidic, a pH of 7 is neutral, and a pH greater than 7 is basic.

pH of Fresh Milk

Fresh milk has a pH of 6, which means it is slightly acidic.

Fermentation Process

When milk turns into curd, it undergoes a fermentation process caused by bacteria which convert lactose into lactic acid.

Effect of Lactic Acid

Lactic acid is more acidic than fresh milk. As the concentration of lactic acid increases during fermentation, the pH of the milk decreases.

Predict the pH Change

Since the production of lactic acid increases as milk turns into curd, the pH will drop, making the curd more acidic compared to fresh milk.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

pH scale

The pH scale is a tool used to measure how acidic or basic a substance is. This scale ranges from 0 to 14. A pH of 7 is considered neutral, meaning it is neither acidic nor basic. Substances with a pH less than 7 are acidic, and those with a pH greater than 7 are basic (also known as alkaline). The lower the pH, the more acidic the substance is. For example, lemon juice has a pH around 2, making it very acidic, while baking soda has a pH around 9, making it basic.

fermentation process

Fermentation is a biological process where microorganisms like bacteria or yeast convert sugars into different substances. In the context of milk turning into curd, certain bacteria (lactic acid bacteria) play a crucial role. These bacteria feed on lactose, the sugar found in milk. During this process, they convert lactose into lactic acid. This fermentation process not only changes the texture of the milk, causing it to thicken and form curd, but also impacts its chemical composition, notably its pH level.

lactic acid production

Lactic acid production is a key part of the fermentation process. When lactic acid bacteria break down lactose in milk, they produce lactic acid as a by-product. Lactic acid is what gives curd its slightly tangy taste. Because lactic acid is more acidic than fresh milk, its production lowers the pH of the milk. This increase in acidity helps in preserving the milk and also plays a role in the formation of the curd's texture. The more lactic acid produced, the more acidic the milk becomes.

acidity in curd

The acidity in curd is a direct result of the lactic acid produced during fermentation. As fresh milk with a pH of around 6 undergoes fermentation, the production of lactic acid increases. This decrease in pH makes the curd more acidic compared to the original milk. The change in pH not only affects the taste, giving it a tangy flavor, but also helps in its preservation. The higher acidity helps to inhibit the growth of harmful bacteria, making curd a safer food option. So, in summary, as milk turns into curd, its pH drops, making the curd more acidic.

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Fresh milk has a pH of 6 . How do you think the pH will change as it turns into curd? Explain your answer.

Short Answer

Step by step solution

Understanding pH

pH of Fresh Milk

Fermentation Process

Effect of Lactic Acid

Predict the pH Change

Key Concepts

pH scale

fermentation process

lactic acid production

acidity in curd

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