Abstract
Changes of flavor components in crushed dried bonito during storage under various conditions were examined, and key compounds for the deterioration were clarified by GC analysis and addition tests of volatile compounds.
Rancid odor came up from crushed dried bonito which had been kept at -20°C for 24 days, whereas it was very weak in that kept at 70°C for 4 hours.
Volatile compounds in the stored samples were absorbed on Tenax-TA polymer and analyzed by GC-MS. The amounts of carbonyl compounds increased during storage in all samples kept under any conditions described before, but the composition of carbonyl compounds depended on the conditions. The amounts of straight-chain aldehydes such as pentanal and hexanal increased in the crushed dried bonito kept at -20°C. On the other hand, at 70°C these aldehydes were not detected and branched chain aldehydes and ketones increased. When these compounds were added to crushed dried bonito and heated, straight-chain aldehydes decreased most markedly.
It was clarified by the experiment using labeled oxygen that oxygen atoms of these carbonyl compounds, which were formed during storage, were derived from the headspace gas or water in dried bonito.
Addition of straight-chain aldehydes such as hexanal to the freshly crushed dried bonito resulted in strengthening the rancid odor. Branched chain aldehydes and ketones did not influence the flavor character. These findings suggest that straight-chain aldehydes might be involved in the deterioration of flavor in crushed dried bonito.
