| Flavor compounds play a significant role in the quality of our food because flavor perception is one of the foremost criteria used by the consumer for the preference or acceptance of a food product. Marine products have different characteristic flavor, and the flavor-active components have been identified by means of modern analysis instruments using the flavor extracts.An incredibly expensive delicacy in China, the puffer fish, a representative migration fish, has been praised as one of the three most delicious fishes in Yangtze River. It has been reported that there are 8 edible species of farmed pufferfish, because of their low(or even zero) TTX level. A typical example of an edible pufferfish in China is the farmed Takifugu obscurus. Cooked Takifugu obscurus muscle has a characteristic flavor and is used as a material for making soup in China and other Asian countries. On formal occasions, Takifugu obscurus is eaten regionally in China, for example, boiled Takifugu obscurus, which is one of the New Year dishes of south Jiangsu, is based on soup stock from boiled Takifugu obscurus muscle with fried liver. To date, the components determining the key odor of pufferfish have not been reported. Moreover, almost no information is available on the possible effects of edible liver on the flavor of pufferfish. Various methods, such as steam distillation under reduced pressure, solvent extraction, and solid phase micro extraction, have been used for the extraction and determination of volatile compounds in fish products. In the present study, simultaneous distillation–extraction(SDE) and monolithic material sorptive extraction(MMSE) were applied for the extraction of volatile compounds from heated obscure puffer(Takifugu obscurus) liver and their effects were compared. The better one combined GC-MS and GC-O was employed to analyze the volatile compounds in obscure puffer meat, liver and soup. And the main nitrogenous taste components were also analysed in this study. The results were as follows:1. SDE and MMSE were compared for their effectiveness in the extraction of volatile compounds from steamed obscure puffer(Takifugu obscurus) liver. Total 88 volatile compounds were identified, including 13 aldehydes, 14 N-or S-containing compounds, 5 ketones, 7 alcohols, 13 aromatics, 33 hydrocarbons, 2 esters and 1 acids. As demonstrated by a comparison between both extraction techniques, a higher level of hydrocarbons, aldehydes and aromatics were detected using SDE, while MMSE gave rise to a higher level of aldehydes and N-or S-containing compounds. MMSE combined GC-MS was employed to analyze the volatile compounds in obscure puffer liver. 46 compounds were identified in steamed Takifugu obscurus meat, 59 compounds were identified in boiled Takifugu obscurus meat, 43 compounds were identified in steamed Takifugu obscurus liver, 54 compounds were identified in fried Takifugu obscurus liver and 37 compounds were identified in Takifugu obscurus soup. According to the literatures, the results indicated that a total of 9 compounds(OAV>1) were founded in Takifugu obscurus meat, liver and soup simultaneously, which were trimethylamine, decanal, 1-penten-3-ol, 3-methyl-butanal, hexanal, benzaldehyde, octanal, nonanal, 2-ethyl-furan. Trimethylamine, decanal and dimethyl disulfide contributed actively to the flavor of farmed Takifugu obscurus meat. 2-Methyl-naphthalene, 2-ethyl-furan and trimethylamine contributed actively to the flavor of farmed obscure puffer liver. Trimethylamine, decanal and nonanal contributed actively to the flavor of farmed obscure puffer soup.2. The odor compounds in Takifugu obscurus were extracted by MMSE and analyzed by gas chromatography-mass spectrometry-olfactometry(GC-MS-O). 68 odor compounds were detected and identified, including 22 compounds in steamed meat, 19 compounds in boiled meat, 27 compounds in steamed liver, 37 compounds were identified in fried liver and 41 in soup. Combined with odor-active compounds(OAV≥1), trimethylamine, decanal, nonanal, 1-penten-3-ol, hexanal, 2-ethyl-furan, dimethyl disulfide and 2-undecanone were proved to be key contributions to the flavor of steamed Takifugu obscurus meat. Trimethylamine, 2-ethyl-furan, 1-penten-3-ol, 2-pentyl-furan, dimethyl disulfide, benzaldehyde and 3-octanone were proved to be key contributions to the flavor of boiled meat. 2-Ethyl-furan, trimethylamine, 1-penten-3-one, dimethyl trisulfide, 3-methyl-Butanoic acid, dimethyl disulfide and heptanal were proved to be key contributions to the flavor of steamed liver. 2-Methyl-naphthalene, trimethylamine, nonanal, 2-ethyl-furan, dimethyl trisulfide, 2-pentyl-furan, heptanal and benzaldehyde were proved to be key contributions to the flavor of fried liver. Trimethylamine, octanal, hexanal, 1-penten-3-one, heptanal and benzaldehyde were proved to be key contributions to the flavor of soup.3. Non-volatile flavor substances of the Takifugu obscurus were analysed systematically, including free amino acids, flavor nucleotides, TMAO and betaine. When heated, the order of contents of the umami free amino acids contribution on the taste of meat: steamed(7.39) > raw(5.29) > boiled(2.75); liver: fried(21.78) >steamed(15.79) > raw(8.03). The umami amino acids in Takifugu obscurus liver was richer than meat, and fried heating improved the contents of the umami free amino acids. In flavor nucleotides, TAV value greater than 1 in Takifugu obscurus was IMP of fish meat. The order of TAV of IMP contribution on the taste of meat: steamed(21.60) > raw(10.11) > boiled(7.04); liver: fried(0.41) > steamed(0.37) > raw(0.01). TMAO and betaine had important contribution on the taste of Takifugu obscurus. Finally, the umami synergy analysis of the main umami free amino acids and nucleotides showed that the monosodium glutamate equivalent(EUC) of Takifugu obscurus soup was 0.37 g MSG / l00 g, and the sapidity strength value was 12. All of this were benefit from the IMP in meat and umami free amino acids in liver, which also explained the well taste of Takifugu obscurus soup. |
PDF Full Text Request