Manufacture of fish sauces and pastes

The general procedure for the production of fish sauces is not complicated.The starting material can be small (<15 cm in diameter) fish,

Table 12.9. Types of fish sauces and pastes.

Product

Country

Description

Nam-pla

Thailand

Fish sauce

Budu

Malaysia

Fish sauce

Patis

Philippines

Fish or shrimp sauce

Ishiru

Japan

Fish sauce

Nouc-mam

Vietnam

Fish sauce

Nam-pa

Laos

Fish sauce

Bagoong

Philippines

Fish or shrimp paste

Mam

Vietnam

Fish paste

Trassi

Indonesia

Shrimp or fish paste

Belachan

Malaysia

Shrimp paste

such as sardines (that otherwise have minimal commercial value), small shrimp, squid, or oysters (Figure 12-7). Fish is usually used whole and uneviscerated, although de-headed, eviscerated, ground, or cut-up pieces can also be used. The only other ingredient necessary to make these products is salt.The fish-to-salt ratio varies, depending on the product, but usually ranges from 3:1 to 5:1. Fish sauces do not undergo a lactic fermentation, per se, and are preserved mainly by salt and low water activity, rather than by pH. Thus, high salt concentrations are necessary.

After the salt is added to the fish (on wooden or concrete floors), the mixture is moved into tanks (often built into the ground) and covered. The material is held for about six months (or longer) at ambient temperature. At various times, the mixture may be uncovered, stirred, and exposed to air and sunlight, all of which are thought to improve flavor and color and accelerate enzyme activity. During this incubation period, the solid fish material is transformed, or more precisely, liquefied by the action of endogenous fish enzymes. These enzymes, primarily trypsin-like acid-proteases and various endo- and exo-peptidases, are ordinarily present within the intact cells of various fish tissues. However, in the non-living animal, the cells soon autolyze and those enzymes are released, result-

Figure 12-7. Fish sauce flow chart.

ing in extensive hydrolysis of muscle tissue. In fresh fish, autolysis and proteolysis result in tissue softening and spoilage; in fish sauce production, the result is liquefaction.

In addition to the physical transformation from solid to liquid, proteolytic digestion of the fish substrates results in formation of free amino acids and peptides. In intact tissue, for example, the soluble nitrogen concentration is essentially nil, but in nam-pla and nuoc-mam (Thai and Vietnamese fish sauce, respectively) there is more than 2% soluble nitrogen (mostly amino nitrogen). Glutamic acid, which, like in soy sauce products, is responsible for flavor enhancement, is among the amino acids that accumulate in fish sauce. Likewise, 5'-nucleotides may also be formed, providing a source of umami or meaty-like flavors (as described above).

Further hydrolysis of peptides and amino acids by enzymes that are either endogenous or microbial in origin (see below) eventually results in a large number of volatile aroma and flavor products. Among those that are most prominent and that confer "fish sauce flavor" are ammonia, triethylamine, and various alcohols, aldehydes, ketones, and lactones.Lipolysis also occurs during fish sauce manufacture, resulting in formation of volatile fatty acids, including acetic, butanoic, and propanoic acids. These compounds are particularly characteristic of fish sauce flavor, which is sometimes described as "cheesy."

After several months of enzymolysis and fermentation, the liquid is separated from the sed-imented material by decanting or filtering the liquid directly through the fish solids.This "first run" product has the highest quality. Additional brine can be added to the solid material, the mixture aged for several more weeks (or simply boiled), and then a second, lower quality, liquid is obtained. The remaining solids can then be recovered and used as a paste. Some fish sauces and pastes are aged in the open (and exposed to the sun) for several more weeks to allow partial dissipation of the strong fish aroma.The sauce or paste is then bottled. The final composition (weight basis) of fish sauces is usually about 60% moisture, 30% salt,

10% protein (including amino nitrogen),with a final pH of about 6.5. Pastes contain about 30% moisture, 20% salt, 30% protein, and 20% ash.

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