Abstract:

The present study aimed to investigate the changes in fatty acid composition and volatile compounds of tuna oil
following deodorization by using electronic nose (E-nose) and headspace-solid-phase-microextraction-gas chromatographymass
spectrometry analysis (HS-SPME-GC-MS). Results showed the contents of saturated fatty acids (C14–C22) in tuna
oil decreased whereas unsaturated fatty acids increased following deodorization process. E-nose was able to detect the
changes in volatile compounds of tuna oil with high sensitivity. Before and following deodorization at 150 and 200 ℃, a
total of 50, 38 and 21 volatile compounds namely alcohols, aldehydes, ketones, esters, hydrocarbons, acids and heterocyclic
compounds were identified using GC-MS. The major volatile compounds in tuna oil were identified as octanal, nonanal,
(E)-2-octenal, 1-penten-3-ol and 2-undecanone, which contributed to the unpleasant earthy and fishy smell of tuna oil.
Following deodorization at 150 ℃, the amounts of octanal, nonanal and (E)-2-octenal in tuna oil significantly decreased,
resulting in a significant decrease in its unpleasant earthy and fishy smell, whereas 10-dodecyn-1-ol and 2-butyl-1-octanol
significantly increased, giving a characteristic woody and fatty aroma. A higher deodorization temperature of 200 ℃
significantly decreased the contents of octanal, (E,E)-2,4-heptadienal and (E)-2-decene aldehyde and increased the contents
of tetrahydro-2H-pyran-2-methanol, 2-ethyl-furan, and 2-pentyl furan in tuna oil. Tetrahydropyran-2-methanol, 2-ethyl furan
and 2-pentyl furan were responsible for the fatty, grass and green aroma of tuna oil.

Key words: deodorization fish oil, electronic nose, headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), fatty acid, volatile compounds