Curd has more vitamin B12 than milk because the lactic acid bacteria (LAB, mainly Lactobacillus) that turn milk into curd make extra vitamin B12 while they grow. So fermentation improves the nutritional quality of milk. Memory hook: "LAB is a tiny B12 factory" — the bacteria eat, grow, and leave behind more B12 than plain milk had.
Lactobacillus (LAB) ferments milk into curd and, while growing, produces extra vitamin B12 — so curd has more B12 than milk.
Your doubts, answered
Which vitamin increases when milk is converted to curd?
Vitamin B12. NCERT clearly states that converting milk to curd 'improves its nutritional quality by increasing vitamin B12'. It is not vitamin A, D or E. This one line is directly tested in NEET, so remember only B12.
Why does the vitamin B12 increase in curd?
Because the lactic acid bacteria (Lactobacillus and other LAB) grow inside the milk. As they multiply, their own metabolism produces vitamin B12, so the finished curd ends up with more B12 than the milk you started with. The extra B12 comes from the microbes, not from the milk itself.
Is curd more nutritious than milk because of B12?
Yes, that is the main point NCERT makes. LAB not only coagulate the milk proteins to form curd, they also raise the vitamin B12 content, which makes curd nutritionally better than plain milk. That is why NCERT says fermentation 'improves nutritional quality'.
Does the same LAB also help in our stomach?
Yes. NCERT adds that in our stomach the LAB play a beneficial role by checking disease-causing microbes. So Lactobacillus helps in two ways: it enriches curd with B12, and it protects the gut. NEET can ask either point.
⚠️ The NEET trap ✗ Curd formation increases vitamin A, D or E (the fat-related vitamins). ✓ Curd formation increases vitamin B12 only. This is the exact word in NCERT and the exact answer NEET 2018 wanted. 🧠 Milk-to-curd = B12 up. Ignore A, D, E — the trap options are the other vitamins put there to confuse you.
Real NEET questions
NEET 2018
Conversion of milk to curd improves its nutritional value by increasing the amount of
A · Vitamin B12 ✓
B · Vitamin A
C · Vitamin D
D · Vitamin E
Solution: When lactic acid bacteria (Lactobacillus) convert milk to curd, they improve its nutritional quality by increasing vitamin B12. Vitamins A, D and E are not enriched during this fermentation. NCERT (Ch 8) states curd 'improves its nutritional quality by increasing vitamin B12'.
Solved Microbes in Human Welfare NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
