Studies On Methods Of Determination And Intrinsic Content And Control Of Formaldehyde In Squid Products

The great attention has been paid to volatile toxic aldehydes in theaquatic products, and formaldehyde problem in squid has became serious inChina recently. There are no extremely reliable methods of formaldehydedetermination in the aquatic products in our country, which seriouslyrestricted in monitoring formaldehyde of aquatic product. Based on abovereasons, a high-performance liquid chromatography (HPLC) method wasdeveloped for determination of formaldehyde and ascertained theexperimental parameters of HPLC. Then some differences of HPLC andregular method of acetylacetone spectrophometer had been compared.Furthermore, the instinct formaldehyde contents in 27 samples from fourkinds of aquatic products were determined, including three species visceraand muscle of squids, three species squid threads and four kinds of otherseafoods. The formaldehyde change in the processing of two kinds of squid products and the control of the formaldehyde-producing in the processing ofdried squid thread was studied primarily. Finally, the formaldehyde producingmechanism during the high temperature was studied in squids.Based on steam distillation and 2,4-dinitrophenylhydrazinederivatization, formaldehyde was determined by HPLC analysis usingODS-C₁₈ column at UV detector (355 nm). Detection limit was 8.92μg/L instandard liquid and 0.18 mg/kg in sample, and recovery was 83.09～103.20ï¼…(R²=0.9996), with a better speciality, accuracy and repeatability to HPLCmethod. Compared with two methods of HPLC and acetylacetonespectrophometer, it was found that the determined formaldehyde content wassimilar between 1mg/kg～160mg/kg in samples, but high sensitive method ofHPLC should be recommend below 1mg/kg FA.The intrinsic formaldehyde content of squids, squid products and otherseafish were determined. The results indicated that the formaldehyde contentin viscera and dried squid thread was greatly higher than in flesh of squid.There are visible variations of formaldehyde content among four speciessquids, Argentina squid was the highest both in viscera and flesh. Theformaldehyde content in squid thread products and four kinds of otherseafoods had exceeded the NY5172-2002 formaldehyde standard about10mg/kg in China.Formaldehyde formation and variation in each step and entire processingtechniques were detected. The results showed that there was relatively higherformaldehyde content near viscus and gristle along the vertical and horizontal direction respectively, homologous content in the longitudinal distribution. Inthawed raw material, formaldehyde content in inner and outer sides was lowin the vertical distribution and longitudinal distribution was identical. And itwas identical in semi-finished product. There was a variational significantlytrend of formaldehyde in process of dried squid thread, increased in thecooking and baking steps. The formaldehyde content was about 4.51 mg/kg inraw material, however, it reached about 14.39 mg/kg in finished productbased on water material. However, the formaldehyde content had not changedobviously in raw material and finished product of squid ring processingtechnology.Two steps of cooking and baking, formaldehyde rose most quickly, wereconsidered as critical control points. In the cooking step, the formaldehydecontent increased with the time lengthened gradually. However, the relativehigh temperature and short-time could decrease the formaldehyde produced.Meanwhile, formaldehyde rose continuously with the temperature increased,but decreased distincly after 120℃in the baking. Therefore, the optimalcondition of the two steps were cooking at 90℃for 4min and baking at 125℃,which formaldehyde formation could be effectively controlled in theprocessing of dried squid thread. The formaldehyde content in squid rawmaterial and finished product were 2.50mg/kg and 8.70mg/kg, respectively,through above improved processing technology.The formaldehyde producing mechanism during the high temperaturewas studied. The content change trends of formaldehyde (FA), dimethylamine (DMA) and trimethylamine (TMA) were compared squid with hakes, afterheating in 100℃. Differing form the hakes, the content of three chemistrysubstances increased during high temperature (100℃) in squid. The morecontent of FA, DMA and TMA in squid were produced, the higher heatingtemperature and the longer heating time. Moreover, the three high reactionproducts of FA, DMA and TMA were detected in TMAO standard solutionduring heating condition, with TMAO content decreasing. The resultsindicated that the formaldehyde in heated squids could come from chemicaldecomposition of TMAO.