Sweetened black vinegar (甜醋): a Cantonese confinement staple
tian cu (甜醋)
Sweetened black vinegar is the base of the famous pork trotter dish. What it is, why sweetened not plain, which brand to buy, and the pot it must not touch.
If red date tea is the everyday drink of confinement, sweetened black vinegar is the taste of its most famous dish. The Cantonese pork trotter braise lives or dies on this one ingredient, and it is worth knowing before you cook.
Why sweetened, not plain
This is the decision that determines whether the dish works. Sweetened black vinegar is made specifically for the trotter braise: it is already balanced with sugar, so it simmers down round and mellow. The plain black vinegars, Chinkiang, Pearl River Bridge, Koon Chun, are made for dipping dumplings and dressing noodles. They are sharply sour, and correcting them with sugar takes so much that the result tastes flat and syrupy rather than deep.
Most families buy a bottle of the sweetened kind, with a little unsweetened added back for edge. The brand people reach for is Pat Chun, sold at any Chinese grocer.
Its traditional role
In TCM, black vinegar is classed as warm and sour, and is traditionally said to move blood and disperse stasis, which is why the trotter dish belongs to the later stage of the month, once the body is understood to have finished clearing.
It also does two practical things across the long simmer the dish demands. The acidity draws calcium and minerals from the trotter bones into the sauce, and it acts as a preservative, which is why the dish could traditionally be made in a big batch before the birth and kept for the weeks after, improving as it sat.
One kitchen rule
Because it is acidic, sweetened black vinegar reacts with aluminium and bare cast iron, taking on a metallic taste and damaging the pot. Cook it only in clay, enamelled cast iron or stainless steel.
Sweetened black vinegar is the base of pork trotter in ginger and black vinegar, where the full method lives. For where that dish sits in the month, see how the 30 days are structured.
Common questions
What is the difference between sweetened and plain black vinegar?
Sweetened black vinegar is made for the confinement trotter dish, already balanced with sugar so it is round rather than sharp. Plain black vinegars such as Chinkiang, Pearl River Bridge or Koon Chun are made for dipping and dressing; using them for the dish means adding a lot of sugar and still missing the rounded flavour.
Which brand should I buy?
Pat Chun is the sweetened black vinegar most families reach for and the safest choice for the trotter dish. It is sold at Chinese grocers. Look specifically for sweetened black or sweet vinegar rather than plain black vinegar.
Why can it not touch certain pots?
Vinegar is acidic and reacts with reactive metals like aluminium and bare cast iron, which taints the dish with a metallic taste and can damage the pot. Use clay, enamelled cast iron or stainless steel instead.
Can I use it for anything besides the trotter dish?
It is quite specialised, but the sweet-sour sauce is good for braising eggs, and a splash lifts a simple stir fry. Its main confinement home is the trotter dish, and a bottle bought for that will keep well for other uses.