Occurrence of D-amino acids in fish sauces and other fermented fish products

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 fermentation 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 suppressed 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.