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Taste‐active components were determined for a typical first‐grade Vietnamese fish sauce Nuoc mam, of which total content of extractive compounds reached as high as 20 g/ 100 mL. A complete synthetic extract prepared from 35 compounds according to the analytical data reproduced almost satisfactorily the taste of the original fish sauce. From the synthetic extract, 11 compounds were identified to be the taste‐active components by a series of omission and addition tests. The components consisted of glutamic and aspartic acids, threonine, alanine, valine, histidine, proline, tyrosine, cystine, methionine, and pyroglutamic acid. The most effective compound for recreating the characteristic flavor of fish sauce was glutamic acid, followed by pyroglutamic acid and alanine. Many of these components contribute to umami, sweetness, and overall taste of fish sauce. Even though the simplified 11‐component extract reproduced the taste of fish sauce, the taste strength was weaker than that of the complete synthetic extract or fish sauce itself.

A Vietnamese fish sauce Nuoc mam used in the present study was rich in oligopeptides of which nitrogen content accounted for 20% of total nitrogen. The high‐molecular‐weight peptide fractions fractionated by ion‐exchange chromatographies and ultrafiltration enhanced sweetness and umami as well as sourness and bitterness of the fish sauce, and increased several flavor characteristics including continuity, first taste and aftertaste. Thus, it is apparent that large amounts of peptides produced during the long‐term fermentation of fish sauce are responsible for the complicated taste of the sauce. From each fraction, 17 peptides in total were isolated and determined for their amino acid sequences. These di‐, tri‐ and tetra‐peptides synthesized by solid‐ or liquid‐phase method gave any one of bitter, sour, umami taste, or practically no taste in the absence of salt. In the presence of 0.3% NaCl, however, almost all peptides showed sweet and umami tastes. Other than these 17 peptides, there existed many other kinds of peptides in the fish sauce. Thus, these peptides are thought to contribute to the overall taste of the fish sauce.

Free D-amino acids were determined on the 60 fermented fish sauces collected from Southeast and East Asia. Of major D-amino acids, D-alanine, D-aspartate, and D-glutamate, D-alanine was the most abundant and found in almost all fish sauces. Fish sauces from Myanmer contained significantly higher amounts of these D-amino acids than those from six other countries. In fish sauces differing in the fer mentation periods, D-alanine and D-aspartate were highest in the over-aged fish sauce fermented for 22 months.In the 20%-salted fish sauces prepared from sardine and squid, D-alanine increased only in squid preparation in small amount. In the 10%-salted preparations, the D-alanine increase was large in squid preparation along with the high and long lasted viable bacterial count. This increase was largely sup pressed in the case of sardine preparation.All of the other fermented fish products also contained D-alanine which varied largely with products and a small amount of D-aspartate. These data indicate that at least D-alanine use is possible as a molecular marker of bacterial activities in the fermented fish products of low salt concentration.

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