Abstract:

Fatty acid composition in grass carp muscle and their content changes during chilled storage were studied using
gas chromatography-mass spectrometry (GC-MS) to explore the effect of natural light on the amount and composition
of fatty acids in grass carp muscle. The results obtained showed that monounsaturated fatty acids (MUFA) such as
9-octadecenoic acid and 9-hexadecenoic acid as well as polyunsaturated fatty acids (PUFA) such as 9,12-octadecadienoic
acid and 9,12,15-octadecatrienoic acid were continuously degraded during chilled storage. Their relative contents
significantly declined (P ＜ 0.05) with prolonged storage time, resulting in a significant increase in the relative content of
saturated fatty acids (SFA) such as hexadecanoic acid and octadecanoic acid (P ＜ 0.05). Light had significant effects on
the degradation of 9,12-octadecadienoic acid, 9,12,15-octadecatrienoic acid and the content of total PUFAs including ω-3
PUFAs (P ＜ 0.05) , resulting in significantly higher relative contents of hexadecanoic acid, octadecanoic acid and total
SFAs in the light group than in the dark group. However, the contents of 9-octadecenoic acid, 9-hexadecenoic acid, total
MUFAs and ω-6 PUFAs were not significantly affected by light. PUFAs were oxidatively degraded earlier and the extent
of degradation was 6.30% higher than that of MUFAs after 10 d of chilled storage. ω-6 PUFAs were degraded fast and its
degradation extent was higher than that of ω-3 PUFA. Accordingly, the greater the degree of unsaturation of fatty acids, the
faster the degradation rate, and the greater the extent of degradation. The degradation of unsaturated fatty acids deteriorates
the nutritional value of grass carp muscle. Chilled storage in the dark is helpful to prevent lipid oxidation and thus ensure the
nutritional value and processing quality and prolong the shelf life.

Key words: grass carp, fatty acid, light, gas chromatography-mass spectrometry (GC-MS)