Abstract:

This study was done to establish a more efficient method and appropriate conditions for deodorizing loach. For
this purpose, three deodrization methods, namely, olong tea infusion, bakery yeast and yeast extract, were compared with
respect to thiobarbituric acid (TBA) value, trimethylamine (TMA) value and sensory evaluation score. Besides, the odor
compounds of loach were identified and confirmed by gas chromatography-mass spectrometry detector (GC-MS). The
results showed that the efficiency of three deodorization methods was in the decreasing order of yeast extract, oolong tea and
bakery yeast. The suitable treatment conditions with yeast extract, olong tea infusion and bakery yeast were determined as
25 ℃, 1.5 h and pH 6.5; 3% (tea concentration), 25 ℃ and 3 h; and 35 ℃, 0.5 h and pH 6.5, respectively. GC-MS analysis
revealed that a total of 68, 55, 55 and 51 volatile flavor substances were detected in loaches before and after deodorization
with oolong tea, bakery yeast and yeast extract, respectively, with relative contents of aldehydes of 73.71%, 40.17%,
42.66% and 39.76%, respectively, which supported the results of TBA value, TMA value and odor analysis. The off-flavor
substances of loach may include hexanal, heptyl, octyl aldehyde, E-2-octene aldehyde, E-2-nonenal, E-2,4-decadiene,
heptaldehyde, and 2,3-butanedione.

Key words: loach, deodorization, yeast extract, oolong tea, gas chromatography-mass spectrometry (GC-MS)