Study On Flavor Of Seawater Fish Meat And Its Products

China is a fishing giant and has abundant bio-resources with large varieties. Seawater fish, such as yellow croaker, eel and pomfret, are popular with consumers of Zhejiang Province for its delicious taste and rich nutrition. Some convenience fish products, such as crispy yellow croaker, baked codfish fillets, baked eel fillets, are the most popular fish products for its unique flavor and taste. But the off-flavor problem always remains in seawater fish meat, the characteristic fishy flavor of fresh fish has a negative impact on the quality of fish flavor. On the other hand, volatile compounds, which are produced from auto oxidation of polyunsaturated fatty acids in storage and processing, might also have some contribution to fishy flavor. For this, lipid oxidation has been recognized as a leading cause of quality deterioration in fish muscle foods. In this paper, volatile flavor components of seawater fish and its products were studied. The purpose of this study was to obtain the basic chemical information of seawater fish in order to provided experimental data of quality management of seawater fish and a refernece to synthesis of various fish meat flavor. In addition, volatile compounds formed from lipid oxidation of fish muscle were studied and effect of different seasoning on the rate of oxidation were determined. The results obtained from this study provided scientific foundation to prevent the formation of the fishy flavor from the deterioration of fish muscle, and to improve the flavor quality of fish products. The main contents were as follows:First of all, volatile flavor compounds of the five widely eaten sea fishes meat including yellow croaker, eel, codfish, pomfret and spanish mackerel and the seven types of commercial seawater fish products including baked spanish mackerel fillets, baked eel fillets, baked codfish fillets, baked skate fillets, baked yellow croaker fillets and crispy yellow croaker were extracted and identified by headspace solid phase micro-extrac-tion(HS-SPME) and gas chromatography-mass spectrometry(GC-MS). The relative odor activity value(ROAV) in association with odor threshold was applied to confirm the key compounds of different samples. The changes of some indexs including TB A-value, smell and volatile flavor in the baked yellow croaker fillets, as well as the correlativity on the three indexs were studied by Schall experiment. Two indexs including TBA-value and volatile compounds in different baked fish fillets by adding different seasonings(sugar, salt, ginger, yellow rice wine, star anise) were compared. The main results were as follows:(1) 1-Octene-3-ol, pentanal, heptanal,4-heptenal, octanal, benzaldehyde, nonanal, decanal,2,3-octanedione were the key odor compounds of yellow croaker. The flavor of eel were composed of 1-Octene-3-ol,3-methyl-butanal, heptanal, octanal, benzaldehyde, nonanal,2,3-octanedione, ethyl acetate and trimethylamine. The key odor compounds of codfish were 1-Octene-3-ol,3-methyl-butanal, benzaldehyde, decanal,1-octene-3-one, trimethylamine, dimethyl-disulfide. The flavor of pomfret were composed of 1-Octene-3-ol,3-methyl-butanal, heptanal octanal, nonanal, decanal,2,3-octanedione.1-Heptanol, 1-octene-3-ol,3-methyl-butanal, pentanal, Heptanal,4-heptenal, octanal, nonanal, benzaldehyde,2,3-octanedione and ethyl acetate were the key odor compounds of spanish mackerel.(2) Decanal,2,3-diethyl-5-methyl-pyrazine, trimethylamine, 1-octene-3-ol, 3-ethyl -2,6-dimethyl-pyrazine, ethyl acetate, benzaldehyde, octanal,3-methyl-butanal, and hexanoic acid-ethyl ester were the key odor compounds of the baked spanish mackerel fillets. 1-octene-3-one, hexanal, decanal,2,3-Butanediol,1-octene-3-ol and trimethylamine were the key odor compounds of the baked eel fillets.2,3-Diethyl-5-methyl-pyrazine, decanal, 1-octene-3-ol,3-ethyl-2,6-dimethyl -pyrazine, benzaldehyde,3-methyl-butanal, hexanoic acid-ethyl ester,2,3-(?)utanediol, ethyl acetate,2-undecanone, and 2-methyl-butanal were the key odor compounds of the baked codfish fillets.2,3-Diethyl-5-methyl-pyrazine, trimethylamine,3-ethyl-2,6-dimethyl-pyrazine, l-octene-3-ol,3-methyl-butanal, acid ethyl ester and benzaldehyde were the key odor compounds of the baked skate fillets. Trimethylamine,2,3-diethyl-5-methyl-pyrazine, decanal, l-octene-3-ol,3-ethyl-2,6-dimethyl-pyrazine and 3-methyl-butanal were the key odor compounds of the baked yellow croaker fillets. Trimethylamine, decanal,3-methyl-butanal, l-octene-3-ol,2-methyl-propanal,2-methyl-butanal, ethyl acetate, nonanal, benzaldehyde, octanal and heptenal were the key odor compounds of the crispy yellow croaker.(3) The changes of some indexs including TB A-value and volatile flavor in baked yellow croaker fillets were analyzed, and the measured results show that:The contents of hexanal, heptenal, nonanal, l-octene-3-ol as well as TBA-value in the baked yellow croaker fillets increased as the accelerated storage time increased. The increase in four compounds showing the higher correlations with the TBA-value and smell index. According to these results, hexanal, heptenal, nonanal, l-octene-3-ol were preferred as potential markers to evaluate the lipid oxidation in fish muscle.(4) Effect of various seasonings(sugar, salt, ginger, yellow rice wine and star anise) on the change of two indexs including TBA-value and volatile compounds in baked yellow croaker fillets were compared. The results showed that:Different types of seasoning had a significant influence on the rate of TBA-value in the baking process. The TBA-value increased as the concentration of sugar, yellow rice wine, ginger and star anise seasoning increased. The contents of hexanal, heptenal, nonanal, l-octene-3-ol in baked yellow croaker fillets which soaked 7.5% sugar,0.4% ginger and 0.4% star anise seasoning were reduced. Salt, ginger, yellow rice wine and star anise showed the suppressive effect on the rate of lipid oxidation. Salt content showed small effect on the rate of lipid oxidation. Soaked some kind of seasoning in yellow croaker fillets, not only can removed fishy flavor, but also improved the antioxidant capacity of product.