Lipid, Free Amino Acid, and Organic Acid Compositions of Rice Bran-Fermented Sardine

Abstract

Rice bran-fermented sardine, iwashi nukazuke, has been well known as one of the traditional fish products in Ishikawa Prefecture. In this study, lipid, free amino acid, and organic acid compositions of commercially available rice bran-fermented sardine were investigated.
The pH value, moisture content, and NaCl content of the samples ranged from 5.4 to 5.5, from 43.9 to 45.4%, and from 12.2 to 14.1%, respectively. Lipids in the samples showed somewhat high POVs (16.8-22.1meq/kg) and TBA values (63.0-82.1mg/kg).
Major organic acids were lactic and acetic acids, ranging from 443 to 528mg/100g and from 101 to 124mg/100g, respectively. Non-polar lipids (NL) were mainly composed of triglycerides and free fatty acids (FFA): both NL and polar lipids (PL) seemed to undergo enzymatic hydrolysis to release FFA. Major components of PL were phosphatidylcholine and phosphatidylethanolamine, in which percentages of polyenoic acids such as 20:5 n-3 and 22:6 n-3 were relatively high, suggesting that the samples underwent almost no oxidative rancidity during processing and/or storage. These results showed that the lipid deterioration which occurred in rice bran-fermented sardine during processing and/or storage might be attributed to enzymatic hydrolysis rather than oxidation.