Volatiles from the headspace gas of fish sauce with no change in the pH (pH as is) were trapped in a Tenax TA column and analyzed by gas chromatography (GC) and GC-mass spectrometry (MS). Fish sauce was alkalized (pH 11.0) to enhance the release of nitrogenous and sulfurous compounds and was likewise analyzed. About 124 volatile compounds, including 20 nitrogen-containing compounds, 20 alcohols, 18 sulfur-containing compounds, 16 ketones, 10 aromatic hydrocarbons, 8 acids, 8 aldehydes, 8 esters, 4 furans, and 12 miscellaneous compounds, were definitely and tentatively identified. Detection of highly volatile nitrogenous and sulfurous compounds such as trimethylamine and dimethyl disulfide, which could not be easily detected by already existing methods, was enhanced after alkalization. Keywords: Headspace gas; volatile compounds; odor; fish sauce

Volatile compounds in fish sauce were isolated by a column concentration method using Porapak Q and by a simultaneous distillation and extraction method with diethyl ether under reduced pressure. Column concentration isolates were further fractionated by silica gel column chromatography and organoleptically evaluated. About 155 volatile compounds, including 14 acids, 36 carbonyls, 17 nitrogen-containing compounds, and 10 sulfur-containing compounds, were identified. Column concentration could be a suitable method for isolating volatile compounds in fish sauce. Large amounts of acids, large numbers of carbonyls and sulfur-containing compounds, such as, dimethyl sulfide, dimethyl trisulfide, and 3-(methylthio)propanal, as well as many types of nitrogen-containing compounds are thought to be major contributors to fish sauce odor. Keywords: Fish sauce; odor; volatile compounds

Headspace gas chromatography (GC) analysis was used on three brands of Philippine fish sauces (patis) with a non-adjusted pH and pH 11.0. Under alkalized conditions, Iarge amounts of trimethylamine and dimethyl disulfide were detected in samples A and B. Since the pH value of sample B was 0.3 unit higher than sample A, the volatilities of these two compounds were estimated to be about 2 times higher in sample B than in sample A. This estimation could explain the good, fishy smell of sample A and the very fishy and disagreeable smell of sample B. Sample C also included both compounds at low levels, but had higher amounts of pyrazines as compared to samples A and B. The burnt and sweet smell of sample C could be attributed to these compounds combined with large amounts of ketones and alcohols.

Amberlite XAD-2 was selected as a suitable resin for column treatment to remove odorants in fish sauce samples. Amberlite XAD-2 could treat up to 700 times its volume of fish sauce. Headspace gas chromatographic analysis of treated and untreated samples revealed remarkable decreases in each class of volatile compounds