Study On The Control Of Formaldehyde And Improvement Of Process In Dried-seasoned Dosidicus Gigas

The dried-seasoned squid tastes well and is nutritional and very popular as a kind of recreational food in many countries of the world.Along with reduced catches of Todarodes pacificus,the raw materials of dried-seasoned are replaced by Dosidicus gigas which is cheaper and has a large catch amount.Although the change of materials reduces the production costs,it imposes some new problems at the same time.On the one hand ,the content of Trimethylamine oxide (TMAO) in Dosidicus gigas can reach up to 80mg/kg and TMAO will decompose and produce more formaldehyde(FA),what is harmful to people's health.On the other hand,it is not sure whether the traditional processing technology needs new technological parameters and it needs to be researched. At the same time, the moisture content of dried-seasoned squid in the market is low, the toughness is very strong and its mouthfeel is very poor, so it's an important and actual problem to improve its taste and quality.Based on the above reasons, the paper studies the way of non-enzyme degradation of TMAO in Dosidicus gigas and establishes the dynamical model during storage in order to control the content of FA and improve its security.On the other hand,the paper improves the process parameters of cold storage (-10—-5℃) and develop a new kind of high moisture dried-seasoned squid, in order to improve its quality and save the cost of production.Conclusion summarized as follows:1. TMAO standard solution is stable and can't be decomposed at high temperature,but when some reducing agent or irons existes,it can be decomposed and The higher the temperature is, the longer reaction time is, the decomposition of TMAO is more .The decomposition of TMAO is maximum when the pH is 7.0,Both acidity and basicity can inhibit the decomposition of TMAO.The thermal decomposition of TMAO was significantly enhanced when VC, taurine, cysteine and other substances are added with ferrous ions. Among the addition, the complexes of Vc and ferrous ions has the best effect on the reaction in which TMAO is decomposed completely. It's speculated that ferrous ions is the main promoting factor of the thermal decomposition of TMAO. Chelating agent and pH both can affect the promote role of ferrous ion in TMAO decomposition,and When Vc and ferrous ion coexist,lower pH is beneficial to the formation of TMA so as to inhibit the generation of FA. By storage simulation experiment , during the storage period, TMAO decomposed gradually as time goes by and In the first two days the decomposition is rapid but then it proceeds slowly . Iron ions can promote the decomposition of TMAO, and the effect is proportional to iron ion concentration.So in the processing and storage process,Fe²⁺is an important factor which promote TMAO decompositon and FA increasing.The productor needs to minimize the contact of product with metal machine so as to reduce the content of Fe²⁺in the products ,control the degradation of TMAO and reduce FA production speed.2. In order to monitor the change of FA in the dried-seasoned squid during storage, the paper establishes the dynamical model of TMAO, DMA and FA at 25℃, 35℃, 45℃,determine its reaction series to be grade 1 reaction and reaction activation energy are respectively 22778.6 J/mol,31555.0 J/mol,9504.6J/mol.the uncertainty between reaction activation energy improve the complexity of TMAO decomposition. the equations launched by Arrhenius equation are K_B=8.3×105e-31555.0/RT ,K_B=610.3e-9504.6/RT,the R² are all big than 0.98.it has high reliability and lays a foundation for the limited standards of FA in the aquatic products and for the control of FA during shelf life.3. By studying the mechanism of Cold storage ,the paper proves that the chemical and physical properties of fiber protein changes dramatically with protein denaturation and the change of space structure,and form a loose, stable network structure so as to ensure the product intact, uniform, fluffy. Based on the change of EPN ,space structure and TMAO,TMA,DMA,the paper determines the optimal time of cold storage is 3-6 days, so that the processing cycle is shortened greatly.4. By lowering the water activity(Aw),the paper developes a new kind of water activity lowering agent . Through the analysis of low field nuclear magnetic resonance (NMR), Water activity reduced because of the change of moisture state with the reduction of free water and the increasing of middle water . High moisture samples with different Aw produce FA with a different rate.So reducing water activity can slow the rate of increasing of FA and improve the safety of dried-seasoned squid.