Correct answer: (1) Rennet

Rennet is the classic milk-clotting enzyme preparation used in cheese production. It contains the protease chymosin, which specifically cleaves κ‑casein, destabilizing casein micelles and causing milk to coagulate into curd while separating whey.

Option-wise explanation:

• (1) Rennet

  • Rennet (rich in chymosin) is the primary enzyme used to coagulate milk in most traditional and industrial cheeses.

  • By cutting κ‑casein, it allows casein micelles to aggregate and form a firm curd, which is then processed into cheese.

  • Therefore this is the correct answer.

• (2) α-Amylase

  • α-Amylase breaks down starch into smaller sugars.

  • It is widely used in baking, brewing, and starch processing, not for milk coagulation in cheese making.

• (3) Lactase

  • Lactase (β‑galactosidase) hydrolyzes lactose into glucose and galactose.

  • It is used to make lactose-free milk and dairy products, but it does not clot milk or form curd for cheese.

• (4) Trypsin

  • Trypsin is a serine protease from the pancreas, used in protein digestion, cell dissociation, and lab protocols.

  • It is not the standard milk-clotting enzyme in cheese technology.