Tangerine peel

The Chinese name is the argument. 陈皮 means aged peel, not tangerine peel — the first character is the one used for old wine and old friends. Fresh citrus peel is not the same item. The tradition holds that this is one of the few things in the pharmacy that improves with keeping, and Chinese households have stored it the way other households store spirits.

Xinhui county in Guangdong is the origin that carries the reputation, and aged Xinhui peel is priced by the decade in exactly the way a vintage is. Three years is the usual minimum before anyone calls it chenpi at all. Old peel is dark, brittle, curls at the edges and smells of orange oil only faintly; young peel is bright, flexible and smells like a marmalade factory. The old is what a Chinese cook wants.

What it does in the classical vocabulary is move qi — 理气 — which is the tradition’s language for the feeling of a meal that has stopped moving. Fullness under the ribs, a sensation of a lump that came from nowhere, belching, a heaviness after eating that arrives regardless of how much was eaten. Nearly every Chinese formula written for that picture has chenpi somewhere in it.

A thumbnail of peel is enough for a whole pot. It goes into red bean soup, into steamed fish, into a braise, into congee. Cantonese kitchens keep a jar of it near the stove and use it the way an Italian kitchen uses a parmesan rind: not a flavour anyone names, but noticeable when it is missing.

Chenpi is warm and drying, and drying is the whole of its character. That makes it good company for a heavy, sticky, over-full sort of feeling and poor company for anything already parched. It is also mild enough that a small amount in cooking is genuinely unremarkable.