Yoghurt is produced with the help of

Options

A. Lactobacillus bulgaricus
B. Lactobacillus thermophilus
C. Streptococcus thermophilus
D. Both (1) and (3)

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which microorganisms are involved in the production of yogurt.

2. **Identifying the Process**: Yogurt is produced through the bacterial fermentation of milk. This process involves specific bacteria that convert milk sugars into lactic acid.

3. **Recognizing the Key Bacteria**: The main bacteria involved in yogurt production are:
- **Lactobacillus bulgaricus**
- **Streptococcus thermophilus**

4. **Explaining the Fermentation Process**:
- These bacteria ferment lactose (the sugar found in milk) into lactic acid.
- The production of lactic acid lowers the pH of the milk, causing it to clot and form the characteristic texture of yogurt.

5. **Evaluating the Options**:
- Option 1: Lactobacillus bulgaricus - Yes, it is used.
- Option 2: Lactobacillus thermophilus - Not specifically mentioned in the context of yogurt production.
- Option 3: Streptococcus thermophilus - Yes, it is used.
- Option 4: Both 1 and 3 - This is correct since both Lactobacillus bulgaricus and Streptococcus thermophilus are used in yogurt production.

6. **Final Answer**: The correct answer is "both 1 and 3" as both Lactobacillus bulgaricus and Streptococcus thermophilus are essential for yogurt production.

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