| Recently, with the emergent of security incidents in endlessly, the great attention has been paid to food safety of aquatic products. Among of those incidents, the security problem of formaldehyde (FA) in squid was particularly serious in China, which had become an important problem demanding prompt solution, and had badly affected the survival and development of squid industry and even the whole aquatic product processing industry of China. So, the work that proving up the generation mechanism of FA during the processing progress of squid products to develop the methods of controlling FA content for the safety processing of squid products, has become an urgent task.In view of these situations, a study of the generation mechanism of FA during the processing progress of squid products was done in this paper. First, to monitor trimethylamine oxide (TMAO) thermal conversion, the contents of FA and Dimethylamine (DMA) were measured. Second, the effect of temperature, pH, heating time on the thermal conversion of TMAO in Jumbo squid was studied and the differences of thermal conversion of TMAO between cod and Jumbo squid were compared. The additives experimentation was used to screen out the inducement factor in thermal conversion of TMAO. Then in vitro model of TMAO-Fe(II) was established to eliminate disturbing biotic and abiotic factors in organism. Finally, ESR was applied to determine the free radical produced by thermal decomposing of TMAO in various systems and the thermal conversion mechanism of TMAO was confirmed by contrasting the signals among various systems. This work aims at providing scientific basis and basic data for controlling the FA content of seafood. The safety of squid products was increased. It was good for development of enterprise in ZheJiang province.A GC-FID method for determination of DMA in sea food was estabilished. The method of extraction, preparation and analysis were discussed. The sample was extracted by 7.5 %TCA.The supernate and p-touluenesulfonyl chloride were reacted for 1 hour at 60℃.And the product of derivatization was analyzed under the determinate GC method. The result of methodology indicated that regression factor was 0.9998 in the concentration range of 0.001 mg/mL-2.000 mg/mL,The intra-day RSD were within 2.8 %, The inter-day were within 5.0 %.The Limit of detection for DMA was 0.38μg/mL.The limit of quantitation was 0.71μg/mL.The recoveries were between 90.21 %-103.24 %. This method was high sensitivity,as well as easy operation.The regularity of thermal conversion of TMAO to FA and DMA in Jumbo squid was studied. Apparently, the thermal conversion of TMAO to DMA and FA in supernatant of squid was high-temperature dependent. The optimal pH of the decomposed of TMAO was pH 7.0. Under extreme acidic or alkaline conditions, the increases of DMA and FA were not significant. The thermal conversion of TMAO was processing as the heating time prolonged. It couldn't stop until heating 90 min.These proved that the thermal conversion of TMAO was belonging to the non-enzmic pathway. The differences of TMAO conversion between Jumbo squid and cod were studied. The effects of various factors on TMAO conversion were examined. Among various compounds used in this study, three substances, such as Cys, Vc and FeCl2 exhibited a remarkable increase on FA content, especially FeCl2.The effects of promoter were not relative to reductive potents. Fe2+ was the most important factor for thermal conversion of TMAO in Jumbo squid.The aqueous solutions of TMAO and promoters (Cys, Vc, FeCl2) were mixed respectively to do the simulate experiments. Among three compounds used in the study, only Fe2+ could induce TMAO decomposed. So the model system was estabilished as TMAO-Fe(Ⅱ) system. The regularity of thermal conversion of TMAO-Fe(Ⅱ) system was studied. It indicated that The regularities of TMAO decomposed between Jumbo squid and TMAO-Fe(Ⅱ) system were the same. TMAO-Fe(Ⅱ) system was feasible.The radical which was relating to formation of FA and DMA in Jumbo squid was determined by ESR. The results were that (CH3)3N·radical was produced when FA and DMA formed in Jumbo squid during heating treatment. For identification of the formed relationship between (CH3)3N·radical and FA, the regulars of (CH3)3N·radical were studied in TMAO-Fe(Ⅱ). Among of them, the formed regulars of (CH3)3N·radical were increased when the temperature was increased. This regular was according to the formed regular of FA and DMA. The signal intense of (CH3)3N·radical was decreased in 10 min,and then decreased slowly. This paper indicated that there was a radical reaction in TMAO thermal conversion in Jumbo squid. |
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