The raw material is small marine fish of the family
Engraulidae or the genus
Corica. Whole fish are mixed with 30–50 percent salt (by weight) and packed into jars or concrete tanks under lids and weight. Protein breakdown is almost complete after a few months; commercial ageing is usually 12–18 months. In the first pressing or first grade, the first liquid drawn off, and sugar is added before bottling. In the second pressing or second grade, brine and an amino-acid solution are added to the residue and allowed to steep 5–15 days. The liquid is bottled with a small amount of acetic acid. In the third pressing or third grade, the remaining solids are boiled with brine and treated with acetic acid and amino acids. The final price is roughly one-third that of first-grade. Some makers use
freshwater fish from the
Chao Phraya basin; the spent mash from this process is mixed with roasted-rice powder and rice bran and sold as
pla ra (fermented fish paste). Artificial, caramel-coloured “fish sauces” made without fermentation were banned in the 1980s. == Culinary use ==