Determination of volatile compounds in different parts of grass carp using GC✕GC-MS combined with chemometrics

The flavor of freshwater fish, which is a highly complex mixture of volatile molecules in varying concentrations, has a nasty and earthy odor. Many compounds of freshwater fish cannot be differentiated due to insufficient separation in traditional one-dimensional gas chromatography-mass spectrometry (GC-MS). This study employed an improved method to detect volatile compounds in different parts of grass carp, including the dorsal meat, skin, intestines, belly, fins, and gills. Comprehensive two-dimensional gas chromatography-mass spectrometry (GC✕GC-MS) with high resolution power was utilized to fully separate the volatile compounds. Additionally, an in-house written script based on Matlab and chemometrics was used to conduct large scale and untargeted studies on volatile compounds. The results demonstrated the superior capability of GC✕GC-MS in identifying a greater number of volatile compounds. The in-house written script was used to automatically compare the same compounds from different samples. Through OPLS-DA analysis, 51 key volatile compound candidates, including dihydrojasmone, cryptomeridiol, (Z,Z)-3,6-nonadienal, 3,5-octadien-2-one, and others, were identified as the most-influential variables in differentiating different parts of grass carp. PCA analysis revealed that the 51 key volatile compound candidates still retained information about the origin of different parts, despite their low concentration. Furthermore, expect that most of these compounds have been found in fish or fish-related products, some may originate from plants, insecticides, or pollution.