Identification Of Characteristic Aroma-active Compounds In Meat Of Cultured Puffer Fish (Takifugu Obscurus)

Cultured puffer fish have distinctive aroma and desirable taste, and there have beensaids that “Has been eating puffer fish, nothing is fresh” and “Desperate to eat puffer fish”.For a long time, there is a habit of eating puffer fish in China. Puffer fish are alsoconsidered as a delicacy cuisine in Japanese and Korean. In recent years, with the successof artificial breeding technology, puffer fish are becoming more and more popular amongdomestic and foreign consumers mainly due to their no tetrodotoxin level in the meat,distinctive aroma, desirable taste, abundant collagen and high nutritional value. People havemore and more high voices to open up puffer fish market. The economic value of pufferfish is becoming increasingly prominent. However, very few studies on flavor of puffer fishwere reported although the researches were mainly focused on the detection of TTX, safeconsumption of pufferfish and the evaluation of nutritional quality of puffer fish. Therefore,it is important to identify the volatile compounds and furthermore to find out thecompounds responsible for the special flavor in the steamed meat of puffer fish. And it isalso important to explore the taste and flavor in different breeding environment and toprovide guidances for puffer fish farming and processing, as well as improving the quality.Puffer fish has a large market potential as well as outstanding economic value and socialvalue, for their large size of individuals and fast growing speed.There will be verysubstantial benefits if these reseach results combine with market efficiency.After all, theproduction and sales of puffer fish are tremendous in Asia. If we have unique technologyadvantages in flavor and storage, we will be able to open up foreign markets, and theexports will also be greatly improved. In the present study, the volatile compounds insteamed meat of farmed obscure puffer were isolated by three extraction methods (SPME,SDE and TD), and analyzed by GC-MS. So as to lay the foundation for cultured Takifuguobscurus, it is very important to establish a fast, accurate and simple volatile compoundsextraction method. The SDE is the better method among the three extraction methods. Thedichloromethane has a good effect comparing with the diethyl ether. The volatilecompounds of three different cultured puffer fish by SDE-GC-MS are compared, combined with sensory evaluation and electronic nose. After the volatile compounds were furtherconcentrated, the odor-active compounds in the extracts were analyzed by GC-MS-O andquantitatively determined by GC. Based on the posterior intensity of GC-O and odoractivity value (OVA) of each odor-active compound, the key compounds that responsiblefor the flavor of steamed meat were estimated. The results will shed a light on the culturedTakifugu obscurus production and provide the scientific foundation on the special flavorquality assessment of cultured Takifugu obscurus.The results are as follows:1. The volatile compounds of steamed meat in farmed obscure puffer (Takifuguobscurus) were isolated by simultaneous distillation and extraction (SDE, dichloromethaneand diethyl ether as solvents, respectively), solid phase micro extraction (SPME) andthermal desorption (TD), and analyzed with gas chromatography-mass spectrometry (GC-MS). A total of101volatile compounds were identified under3different conditions by GC-MS analysis including31aldehydes,14alcohols,11ketones,21N-or S-containingaromatic compounds,16alkanes,3esters, and5acids. Among these volatiles identified,74volatile compounds were extracted by SDE with dichloromethane and diethyl ether，with56compounds by SDE (dichloromethane) and54compounds by SDE (diethyl ether).36compounds were extracted by SPME and22compounds by TD.6compounds wereextracted by the three methods.16compounds were only extracted by SDE(dichloromethane), and14compounds were only extracted by SDE (diethyl ether).16compounds were only detected by SPME and10compounds only by TD.The threemethods have their advantages and disadvantages, therefore, the three methods should becombined in order to get a comprenhensive evaluation of the volatile compounds. SDE isthe better pre-treatment method among the three methods. The dichloromethane isdetermined as the extraction solvent.2. The three puffer fish extracts were analyzed by GC-MS.56compounds wereidentified in Takifugu obscurus,52compounds in Takifugu flavidus and57compounds inTakifugu rubripes. According to the results identified, aldehydes, alcohols, ketones, N-orS-containing compounds and aromatics, acids, alkanes, and esters are the main compoundsin the puffer fish. Aldehydes comprised the mainly group of compounds in Takifuguobscurus, and alcohols comprised the mainly compounds in Takifugu flavidus, while inTakifugu rubripes the content of alkanes is relatively higher. The numbers of N-or S-containing compounds are the same in three puffer fish. However, these compounds haverelatively large differences.The three puffer fish can be distinguished by electronic nose. Bythe PCA analysis, the main volatile compounds in the three types of puffer fish are different. By cluster analysis, results showed that Takifugu obscurus are closer to Takifugu flavidus.In order to evaluate the most potent aroma compounds, the odor activity value (OAV) wasadopted.According to the literatures, a total of17compounds (OAV>1) were founded inTakifugu obscurus,12compounds in Takifugu flavidus, and10compounds in Takifugurubripes.3. The volatile and odor-active compounds in steamed meat of farmed obscure puffer(Takifugu obscures) were analyzed by gas chromatography-mass spectrometry-olfactometry(GC-MS-O). The volatile compounds were extracted by using simultaneous distillation-extraction (SDE), then separated and identified by GC-MS. Odor-active compounds in theSDE extract were characterized by GC-MS-O. The results showed that a total of68volatilecompounds were found including23aldehydes,10alcohols,9ketones,17N-or S-containing compounds and aromatics,3acids,3alkanes, and3esters. In which,31odor-active compounds were detected and identified. Trimethylamine (fishy),1-octen-3-ol(roast),2-ethyl-1-hexanethiol (cooked fish),2-acetylthiazole (meaty), N,N-dibutylformamide (crab meat),2-acetylpyrrole (crab meat) were identified as the key odorcompounds in the cooked meat of farmed obscure puffer based on posterior intensity andtime intensity methods.