Evaluating The Fish Product Freshness By The Ratio Of Volatile Amine And TMAO

After the fish stopping breathing, TMAO which is the substance with characteristicsof flavor in fish can transform it into volatile amine, the method of tradition is usuallymeasured the degree of corruption of fish. The method of using the ratio of volatile amineand TMAO was applied to measure the freshness of fish according to interactions betweenTMAO and volatile amine. The study also established a TMAO model system to study thethermal decomposition characteristics of TMAO from the reaction kinetics, in order tounderstand the mechanism of thermal decomposition of TMAO. The main results of thepaper are showed as followed:1. Bass, turbot, grass carp and tilapia were respectively studied, and the TMAO,TMA, DMA?the ratio of TMAO and volatile amine and FA and other indicators duringstorage at different temperature were tested to analyze feasibility of indicators asevaluation freshness.(1) Different batches of samples with large different TMAO in the initial state of thesamples?and the content of TMAO is influenced by different storage conditions, soTMAO is measured in shelf life at different temperatures are quite different. The contentof TMA is also influenced by individual difference and storage condition. Therefore, thecontent of TMA and TMAO value can not truly reflect the freshness of these four speciesof fish. DMA and FA is not available for quality evolution under cold storage and roomtemperature because of both FA and DMA are the corrupt elements under freezingconditions of these four fish.(2) The ratio of volatile amine and TMAO grew steadily with the increasing storagetime at three storage conditions. It is different to detect the freshness of fish betweenamine and ratio, the ratio of volatile and TMAO can reflects molar mass which TMAOconvert to DMA and TMA. To evaluate the freshness of fish based on the mass of whichTMAO convert to DMA and TMA for avoiding of limition by evaluation of volatile amine.Referring to sensory evaluation, the amount of volatile amine is closed to TMAO whenthese four species of fish reach their shelf life. Therefore, the ratio of volatile amine andTMAO equals1which is defined as warning value, when the ratio over this value, theynot belong to the scope of safe, when the ratio is less than1, the ratio is smaller, thesample is more fresh.(3) Because slow growth in the TVB-N of these four fish under the cold storagemeans lower sensitivity, if taking the TVB-N as evaluation indicator. Due to the effects of cold storage, the microbial growth was inhibited; causing the measured TVC values didnot indicate real freshness after frozen storage for a long time.2. TMAO-Vc and TMAO-Vc-Cys thermal decomposition system were established,adding Cys thermal processing of aquatic products were studied, studying its thermalresponse characteristics, and finally measured TMA, DMA and TMAO content under theconditions of the two systems at different times and different temperatures, to find variousindicators at different stages of Arrhenius activation energy of the reaction. Cys should beavoided adding to the cooking process, and should try to reduce the heating time toprevent the second stage for reducing volatile amines and in order to ensure the qualityand safety of aquatic products.