| Trachinotus ovatus is belong to the perciformes, carangidae, called pompano and golden pompano, which is a rare mariculture fishes, body side is wide and flat, oval, fleshy stingless and tender, fat, bright color. It belongs to the warm water in the upper layer of fish.The optimum temperature of Trachinotus ovatu from 24 to 28 degree centigrade, while 5 to 32 per thousand of salinity can be farmed. It mainly distributed in India, Australia, Japan, America and Chinese, tropical and temperate places such as the Atlantic, the west coast of Africa. It is currently one of the major mariculture varieties in Fujian, Guangdong, Guangxi and Hainan. Its survival rate is high, and its aquaculture production in China is about 7 tons.At present, there are not any integrated public reporting on nutrition, volatile flavor analysis of farmed Trachinotus ovatu.The subject research is to study chemical composition, non-volatile taste components and volatile flavor composition of farmed Trachinotus ovatu, then making a comprehensive evaluation about it. In the end, providing the basic theory for aquaculturing, feed formula, the quality improvement and processing techniques of Trachinotus ovatu.The main conclusions are as follows:1. In order to understand the nutritive quality and nutrient components in the muscle of seawater cultured Trachinotus ovatu, the main nutrient components in the muscle and feed of seawater cultured Trachinotus ovatu were analyzed. Evaluation standards of nutritive quality were based on the Food and Agriculture Organization of the United Nations/Word Health Organization（FAO/WHO） standard mode. The general nutrient compositions were determined by routine methods. Amino acid compositions were determined with an amino acid analyzer. Fatty acid compositions were measured by gas chromatograph-mass spectrometry（GC-MS）. The results showed that crude protein and crude fat of fish feed basically met the nutritional requirements of Trachinotus ovatu. The contents of crude protein, crude fat, crude ash and moisture in fresh muscle of seawater cultured Trachinotus ovatu were（19.48 ± 0.15）%,（8.40 ± 0.30）%,（1.34 ± 0.06）% and（70.84 ± 0.06）%, respectively, while crude fat was higher than other fish species. In dry muscle sample, the total content of amino acids（TAA） was（66.21 ± 1.17）%, and the content of essential amino acids（EAA） was（26.65 ± 0.54）%. Four delicious amino acids（DAA） accounted for（25.50 ± 0.54）%, the ratio of total essential amino acids to total amino acids（EAA/TAA） was 40.25%, and the ratio of total essential amino acids to total nonessential amino acids（EAA/NEAA） was 67.36%. It was clear that the content of different amino acids was stable and the proportions of essential amino acids met FAO/WHO standards. According to nutrition evaluation in terms of amino acids score（AAS） and chemical score（CS）, the first limiting amino acid of both muscle and feed was methionine. In addition, 27 fatty acids were detected in the muscle of seawater cultured Trachinotus ovatu, with PUFA, EPA and DHA accounting for（32.72 ± 0.05）%,（0.64 ± 0.04）% and（5.05 ± 0.23）% of the total amount, respectively. The ratios of n-6/n-3 and PUFA/SFA in muscle indicated its food safety according to the values recommended by the UK Department of Health. Therefore, farmed Trachinotus ovatu is a species of fish with delicious taste, high content of essential amino acids, balanced nutrient composition, high nutrition value for human consumption and health benefits. This study showed that the present feed basically meet the requirements for farmed Trachinotus ovatu growth. However, the quality of farmed Trachinotus ovatu muscle may be improved by increasing thecontents of methionine and n-3 series of fatty acids in the compound feed.2. Major flavour components including nucleotides, free amino acids, inorganic ions and glycine betaine in muscle of sea cage cultured Trachinotus ovatu were determined. Taste impact of the main flavour components were evaluated by taste active value（TAVs） and equivalent umami concentration（EUC） methods. The results showed that the total content of 5’-nucleotides in the Trachinotus ovatu meat was 379.9 mg/100 g, of which 5’- inosine monophosphate（IMP） was up to 373.59 mg /100 mg, followed by AMP（3.25 mg / 100 g）, GMP（2.50 mg / 100 g）, UMP（0.56 mg /100 g）. The total free amino acid is 256.60 mg / 100 The total free amino acid were 256.60 mg/100 g, and of which the glycine, Alanine, Glutamic acid（136.34 mg/100 g, 27.47 mg/100 g, 16.84 mg/100 g, respectively） made the largest contribution to the taste. K+, Na+ and PO43-were the major taste ion. Glycine betaine content was 1.95 mg/g. The EUC of cultured Trachinotus ovatu was 7.92 g MSG/100 g, and the TAV value was 264. Glycine and alanine contributed to the major sweet taste, while glutamicacid and IMP contributed to the strong umami taste. The TAV of Glycine, IMP, K+ and PO43- were greater than one. In conclusion, the main flavour components of Trachinotus ovatu were IMP. Glycine, alanine, glutamicacid, K+and PO43-, while IMP glycine and alanine had synergistic interaction, of which made up the umami of Trachinotus ovatu.3. Headspace solid-phase microextraction method（ HS-SPME） and simultaneous distillation extraction method（ SDE） were respectively employed for sampling in GS-MS analysis of volatile components in Trachinotus ovatu muscle. Totally 88 volatile compounds were identified in Trachinotus ovatu muscles, including 33 aldehydes, 21 hydrocarbons, 11 alcohols, 5 acids, 5 aromatic species, 4 esters, 2 ketones, 2 heterocycles. A total of 51 components were identified by HS-SPME method and 63 by SDE method. There were more aldehydes, esters and heterocycle extracted by SDE than those by HS-SPME, while hydrocarbons,alcohols and ketones extracted by SDE were significantly less than those by SPME. Aldehydes and alcohols, such as hexaldehyde, benzaldehyde, nonanal, 2,6-nonadienal, 1-Octen-3-ol, 1-hexanol and 2-ethyl-1-hexanol made a great contribution to the flavor of cultured Trachinotus ovatu meat. Besides, esters, heterocycle and ketone also affected the odour of it. At the same time, longifolene, butylated hydroxytoluene, p-Xylene, o-Xylene, naphthalene, which from the feed ingredients and cultured environment, also impacted the odour of the meat. A comprehensive evaluation on volatiles in Trachinotus ovatu could be obtained by the combination of both methods. |
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