|Small-Scale Processing of Fish (ILO - WEP, 1982, 140 p.)|
|CHAPTER II. SALTING - DRYING - FERMENTING|
|VII. FERMENTED FISH PRODUCTS|
Fish sauces are basically water-extracted solutions of fully fermented fish and are used in a similar manner to soya bean sauce. Indeed, the manufacture and final composition of many fish sauces is similar to that of soya sauce, it being basically a mixture of protein breakdown products (i.e. peptides, amino acids, amines, etc.) in combination with high salt concentrations. Fish sauces may be of limited nutritional value (van Veen, 1965) as their high salt content precludes bulk consumption. However, in some regions, consumption is surprisingly high and in Viet Nam the sauce nuoc-mam can provide up to 20% of the daily protein intake. Fish sacues are rich in hydrolysed proteins and minerals (e.g. sodium chloride and calcium salts) and can be an important source of calcium in the diet.
VII.3.1. Nuoc-mam (Viet Nam)
Nuoc-mam is by far the most important fish sauce in South East Asia, many thousands of tonnes being produced each year, principally in the coastal regions of Viet Nam, Thailand and Cambodia. Nuoc-mam of good quality is a fairly stable, clear dark brown or amber liquid with a distinctive odour and flavour. The lower quality nuoc-mam may, however, have an unpleasant odour and a reduced storage life. Quite often, additional ingredients are added in order to darken the liquid and improve the flavour of the product. These include such materials as caramel, roasted rice, molasses and roasted or boiled corn. Due to its widespread distribution and consumption, legislation has been introduced in some countries in order to guarantee set quality standards.
The fish species used in the production of nuoc-mam are usually of the genera Stolephorus, Engraulis, Dorosoma and Decapterus and clupeoids. Nuoc-mam can also be prepared from shrimp. The processing method is similar to that of bagoong except that the fermentation is generally protracted and the product is the exudate rather than the solid fraction. The actual process varies according to scale. In the small scale operations, whole fish are kneaded lightly by hand, mixed with salt in earthenware pots and buried in the ground for a few months. The nuoc-mam is the clear liquid which settles on top and is carefully decanted off. In the large scale operations the fish (whole and unwashed) are piled, with salt spread between layers, in timber vats. 4 parts of salt to 6 parts fish should be used for this purpose. After three days, the blood pickle (nuoc-boi) is allowed to flow out slowly over a 3-day period into another recipient. The fish are then trampled by foot until a flat surface is obtained. The latter is covered with coconut leaves over which are set two semi-circular bamboo trays, the whole system being wedged down tightly. The nuoc-boi is then poured back over the fish until a 10 cm liquid layer is formed on the top of the trays. It is then left to mature for four months to a year depending on the species of fish. After maturation, the pickle which is run off is the top quality nuoc-mam. The trays and leaves are removed, and fresh salt is added to the top layer of the fish residue. Fresh brine is also added to obtain a lower quality of nuoc-mam.
The yield varies from 2 to 6 parts of nuoc-mam from 1 part of fish, the residual mass being used as fertiliser. Nuoc-mam is normally packed in bottles but may also be stored in earthenware pots.
VII.3.2. Other fish sauces
A number of other fish sauces are also produced in South-East Asia in large quantities. Patis (Philippines) is produced from the bagoong process and is similar to nuoc-mam. Nam-pla is made in Thailand, the preferred fish species being Stolephorus spp. Production of the latter is similar to that of nuoc-mam although less salt is used (i.e. 1 part salt to 4 parts fish). The process may take from 6 to 36 months to complete depending on the quality required. In Malaysia, a sauce known as budu is made from small anchovies. Production involves mixing 1 part of salt and 5 parts of fish in eartheware pots together with tamarind and palm sugar. A dark, sweet-smelling sauce results after 6 months of fermentation. The product has a storage life of 2 years or more.