| Coilia ectenes is popular for consumers due to its delicious taste. As an anadromous species, Coilia ectenes migrates from offshore water to fresh water areas every year during the spawning season. According to the different capture site, Coilia ectenes population has been identified to three ecotypes. Yangzte Coilia ectenes is famous for its umami taste among Coilia ectenes population, and is known as one of the ―three most delicious fish in the Yangtze River‖ along with two other fish(the hilsa herring and the obscure puffer fish). So far no report was found about umami taste of Coilia ectenes. It has important scientific and practical significance to improve the umami attributes of farmed Yangtze Coilia ectenes and development of the simulation seasonings of the Coilia ectenes by investigating its umami taste.The project contains three parts: Analyzing taste components of Yangtze Coilia ectenes and comparing with that of Yellow River and seawater Coilia ectenes. Identifying of the key umami-related components and investigating their effects on the umami taste of the Yangtze Coilia ectenes by omission and addition test. Verifying the results of sensory experiment by electronic tongue and exploring the feasibility of electronic tongue to predict the amount of the key umami-related components in Yangtze Coilia ectenes.(1) Taste substances in Yangtze, Yellow River and seawater Coilia ectenes steamed meat were analyzed by flame atomic absorption spectroscopy, high performance liquid chromategraphy(HPLC) and amino acid auto-analyzer. Results showed that K+, PO43- and IMP were significantly contributed to the taste of Coilia ectenes meat, and free amino acids attributed to synergistic effects by calculating TAVs(taste activity value) of taste substances. The contents of taste compounds were changed with Coilia ectenes migration from East Sea to Yangtze River and Yellow River. K+ and flavor nucleotides were significant increased, however the contents of Na+, Ca2+, Mg2+, Cl-, PO43- were decreased(p<0.05). It was found that umami was significantly contributed to overall Coilia ectenes taste by calculating EUC(Equivalent umami concentrations). The EUC of both Yangtze and Yellow River Coilia ectenes were significantly higher than that of seawater Coilia ectenes(p<0.05), which might be one of the main reason of migratory Coilia ectenes tasted more delicious than seawater Coilia ectenes.(2) The umami intensity of Yangtze, Yellow River and seawater Coilia ectenes were researched by the method of ranking test. The results showed that the umami intensity of both Yangtze and seawater Coilia ectenes were significantly higher than that of Yellow River Coilia ectenes which were inconsistent with the results from quantitative analysis(p<0.05). Furthermore, the umami scores of both the synthetic extract and the meat extract were significantly higher than the EUC of Yangtze Coilia ectenes according to quantitative descriptive tests. The EUC formula proposed by Yamguchi was commonly used to quantify the umami taste of the synergistic effect between amino acids and nucleotides, however it could not completely express the umami taste in a complex matrix. According to the results from the omission experiment, Glu, Gly, AMP, IMP, GMP, K+, Na+, Cl- and PO43- were identified as key umami-related compounds in Yangtze Coilia ectenes meat, although the degree of their contributions differ from each other. GMP and IMP were found to be more important than the other umami-related compounds from the addition tests. The results showed that the inorganic ions are important for the expression of umami taste in Yangtze Coilia ectenes meat. K+ and Na+ do not produce umami taste by themselves, however, they can increase the umami taste in the presence of umami substances. It is therefore necessary to study the synergistic effect of inorganic ions with the umami components.(3) The umami intensity of Yangtze, Yellow River and seawater Coilia ectenes, the similarity between the synthetic extract and the meat extract of Yangtze Coilia ectenes, the validity of the results from omission test and the feasibility to predict the amounts of the key umami-related components in Yangtze Coilia ectenes were determined by using electronic tongue. The results showed that the umami intensity of both Yangtze and seawater Coilia ectenes were higher than that of Yellow River Coilia ectenes. The taste attributes of Yangtze Coilia ectenes characterized by umami and sweet tastes and the umami intensity between the synthetic extract and the meat extract of Yangtze Coilia ectenes were similar. The results from the electronic tongue generally validated the results from the sensory test, apart from the values for Gly, IMP and Cl-. This suggests that the electronic tongue is generally a good reflection of the umami attributes of samples, but has some limitations when assessing the effects of some taste substances in a complex matrix. Partial least-squares regression(PLSR) was used for prediction model of key umami-related compounds in Yangtze Coilia ectenes. The effects of Gly and IMP prediction were unsatisfactory. It showed that electronic tongue can supplement and verify the results of sensory experiment in a certain extent, but sensory panels still cannot be displaced by electronic tongue. |
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