Fish Sauce Buying Guide: Nitrogen Grade and Origin

This fish sauce buying guide starts with one number: the nitrogen degree on the label. A bottle marked 30N is rated higher than one marked 20N. The number tells you how much nitrogen the sauce holds, and nitrogen comes from the fish protein, so a higher number points to a more concentrated sauce.

Read the nitrogen degree first

The degree is written with a letter N after the number, such as 20N, 30N or 40N. It is a measure of the nitrogen level of the sauce. It does not guarantee good taste, but it does give you a fair way to compare two bottles.

Most fish sauce on the shelf sits in the mid-20s. Anything over 30N is considered high grade, and 40N is described as the best. Treat these as rough guides, not law. Compare bottles only against others of the same degree, or you will be comparing a light table sauce with a rich dipping sauce.

A simple way to pick: use a mid-grade bottle for cooking, where heat and other ingredients hide fine detail. Save the higher degree for dipping, dressings and dishes served cold, where the sauce is tasted on its own.

Sources: Wikipedia, "Fish sauce" and "Nước mắm" (nitrogen level and grade ranges).

Check the ingredient list

Traditional Vietnamese fish sauce is made from fish and salt. The fish is often anchovy. The fish and salt are arranged in wooden barrels to ferment and are slowly pressed, and the salt draws the liquid out of the fish.

A short list is a good sign. Fish, salt, and perhaps water is all a classic bottle needs. Some Vietnamese sauces are made with only anchovies and salt, with no sugar, hydrolyzed protein or preservatives. If the label says high nitrogen and the list is long, ask yourself where the flavour is really coming from.

Look at the order, too. Ingredients are listed from most to least. If water or sugar comes before fish, the bottle may be more diluted than its big number suggests.

Sources: Wikipedia, "Fish sauce" (ingredients, barrel fermentation and pressing).

Look at colour and smell

A good sauce should be clear, with a deep golden amber colour. It should not have a particularly strong smell.

You will also see the words "first press" on some bottles. This means the sauce was bottled from the first draining of the fermenting barrels, which is seen as a sign of quality. The words alone do not prove much, so check the degree and the ingredients as well.

Sources: Wikipedia, "Fish sauce" and "Nước mắm" (colour, smell and first press).

Understand the origin label

Two areas in Vietnam are most famous for making fish sauce: Phu Quoc island and Phan Thiet. A place name on a bottle can draw buyers, so read labels with care.

So read the origin line with care. "Made in" tells you where the bottle was filled. "From Phu Quoc" or a similar phrase tells you where the fish and the work come from. A brand name that uses an island or town name in its logo is not the same as a clear statement of origin. Look for the producer name, the address of the plant and the place of production printed on the back label.

If the claim matters to you, ask the shop where the producer is based. A seller who knows the answer is a better sign than a pretty label.

Sources: Wikipedia, "Fish sauce" (Phu Quoc and Phan Thiet as the two most famous areas).

Buy and store it well

Pick the size you will finish in a reasonable time. A small bottle is better than a large jug that sits open for months. Check that the cap seal is whole and that the label shows the producer, the date of production and an expiry date.

At home, close the cap tightly after each use. Keep the bottle away from sun and heat, in a cupboard or on a cool shelf. Wipe the neck so salt crystals do not build up.

Fish sauce is salty. If you are watching how much salt you eat, use it in small amounts and read the label for sodium. This is general information, not medical advice. Speak to a doctor or dietitian about your own needs.

A quick checklist

When you stand at the shelf, run through these steps in order. First, find the nitrogen degree and decide whether the bottle is for cooking or for dipping. Second, read the ingredients and prefer a short list that starts with fish. Third, check the colour through the glass. Fourth, read the origin line and the producer address. Fifth, look at the seal and the dates. If a bottle passes all five, the price is usually fair for what you get.

Do not chase the highest number. A 40N bottle used in a long stew is a waste of money. A 20N bottle used as a dip may taste thin. Match the grade to the job, and keep a second bottle at home for the other use.

Sources: Wikipedia, "Fish sauce", en.wikipedia.org/wiki/Fish_sauce; Wikipedia, "Nước mắm", en.wikipedia.org/wiki/N%C6%B0%E1%BB%9Bc_m%E1%BA%AFm.