魚醤の絶対値。

こんなコラムがSFChronicleに。

Red Boat Fish Sauceって知らなかったけど、地元Haywardの"cult"な人気の魚醤らしい。で、それ関連で調べてたら、

What does "40N" on my bottle mean?

It has to do with the nitrogen concentration per liter, which is related to the protein level. Above 30N, you’re talking a better, more complex-tasting fish sauce, according to Red Boat Fish Sauce.

Nguyen puts it this way: “I think of them as octane numbers in gasoline,” she says. The higher the number, “the more oomph to it, so you can use a little less.”

How to Buy Fish Sauce Like a Pro | Epicurious

ほぉ、リッターあたりの窒素含有率（タンパク質レベル）。そんな数値があるのか。数値が高いほどキックが強いらしい。ガソリンでいうオクタン価。これで胡散臭い蟹の数、

から開放されるかもｗ。"Red Boat Fish Sauce 40°N"はいつか試してみる。