A young Parmigiano Reggiano can taste milky, while older wheels lean nutty, spicy, or broth-like; what pushes the flavor away from plain dairy?

Answer: Proteolysis

More salt is added — Plausible, but wrong: more salt would be an easy way to make food taste stronger, yet Parmigiano Reggiano's recipe is not built around repeated seasoning. Official and independent tasting descriptions instead tie older wheels to changing texture and aromas. Salt perception may shift, but it does not explain the move from milk notes toward nuts and broth.

Proteolysis ✓ — Right: proteolysis is the engine. As proteins are broken into peptides and free amino acids, the flavor moves from fresh dairy toward more savory and complex notes. The official sensory guide lists milk and yogurt for younger wheels, then nuts, spices, and meat stock for older ones; dairy-science work tracks the peptide changes behind that arc.

Wood adds aroma — Plausible, but not the best explanation: storage environment can matter in many aged foods, so the wooden-shelf guess is understandable. For this cheese, the cited age descriptions and peptide research point more directly to internal ripening chemistry. The flavor arc follows protein breakdown better than a simple outside-aroma story.