Which statement correctly describes rennet used in cheesemaking with respect to its proteolytic enzyme composition?

Introduction:
Rennet is the traditional milk-clotting preparation used to coagulate casein during cheesemaking. Understanding its enzyme composition helps explain curd formation, flavour development, and texture. The terminology around chymosin and rennin can be confusing, but they refer to the same principal milk-clotting enzyme.

Given Data / Assumptions:

• Rennet is derived from calf abomasum or produced via fermentation.
• Major enzymes: chymosin (also called rennin) and pepsin in varying ratios.
• Question asks which description is true.

Concept / Approach:
Chymosin specifically cleaves κ-casein to destabilize casein micelles, forming a gel network. Commercial rennets may contain pepsin as a secondary protease. Therefore, describing rennet as a mixture of chymosin and pepsin is correct, and describing it as a mixture of rennin and pepsin is equivalent because rennin is an older name for chymosin.

Step-by-Step Solution:

Verification / Alternative check:
Label claims and specifications for rennet products list milk-clotting units and composition, typically indicating chymosin content and pepsin percentage. Performance in vat trials corresponds to expected gelation profiles for κ-casein cleavage.

Why Other Options Are Wrong:

• None of the above: Incorrect because both wordings accurately describe rennet.

Common Pitfalls:
Confusing rennin with renin (a kidney hormone) is a common error in terminology. Overuse of pepsin-rich rennet can lead to bitter peptides in aged cheeses due to broader proteolysis; match the enzyme profile to the cheese type.

Final Answer:
Both (a) and (b)