Fish Sauce

Fish sauce is to Thai cooking what salt is to European cooking. Open any Thai kitchen cupboard and there will be a bottle of it, usually more than one, and almost every savoury dish on the table has some in it.

Straight from the bottle it smells strong, even alarming. Cooked into food, the smell disappears and leaves a rounded, savoury saltiness (the taste Japanese cooks call umami) that plain salt cannot give.

How it is made

Small fish, usually anchovies (pla katak), are layered with sea salt in a ratio of roughly three parts fish to one part salt, packed into large concrete or wooden vats, weighted down, and left to ferment in the heat for 12 to 18 months. Enzymes in the fish break the flesh down into a clear, amber liquid.

The first liquid drawn off the vats is the finest, called “first press” or nam pla thae. Later extractions are made by adding brine and pressing again; they are lighter, saltier and cheaper, and are often blended with sugar and flavourings. The coastal provinces of Chonburi, Rayong and Chanthaburi on the eastern Gulf are Thailand’s main producers.

How to cook with it

Fish sauce is usually added towards the end of cooking, then tasted and adjusted. In curries and soups, season once the meat and vegetables are cooked; in stir-fries, add it with the other sauces in the last minute so it can caramelise slightly on the hot wok.

It is also used raw. Mixed with lime juice, palm sugar and chilli it becomes the dressing for yam salads and som tam; with sliced chillies it becomes prik nam pla, the condiment on every Thai table; with lime, garlic and chilli it becomes nam jim seafood, the classic dip for grilled prawns and squid.

A splash in a marinade for grilled chicken or pork (gai yang, moo ping) seasons the meat all the way through and helps it brown.

Grades and brands

Look at the label before the price. Good fish sauce lists only anchovy and salt, sometimes a little sugar. Cheaper sauces add hydrolysed protein, flavour enhancers and colouring.

Colour is a useful guide: clear, reddish-brown like weak tea is good; very dark, murky sauce is usually old or oxidised. Widely available Thai brands such as Tiparos, Squid and Megachef are reliable everyday choices. Vietnamese premium sauces such as Red Boat (made from just anchovy and salt) are excellent for dipping sauces.

Buying and storing

An unopened bottle keeps for years. Once opened, keep it in a cool, dark cupboard and use it within a year; it slowly darkens and its flavour gets stronger, which is harmless. Salt crystals at the bottom of the bottle are normal. Refrigeration is not necessary but slows the darkening.

Substitutes

There is no perfect substitute. Light soy sauce with a pinch of salt gives saltiness and some savouriness. A mashed anchovy fillet dissolved in a little water gets closer. For vegetarian and vegan cooking, use “vegan fish sauce” made from seaweed, mushrooms and soy, or light soy sauce with a little crumbled kombu or nori soaked in it.

Cook’s tip

Season in small steps. Add half of what the recipe says, stir, taste, and then add the rest only if the dish needs it. Different brands vary a lot in saltiness, and too much fish sauce cannot be undone.