Studies On Plastein Reaction Between Hydrolyzed Gelatin And Methionine Lauryl Ester

Hydrolyzed gelatin,also called as collagen polypeptide, is a kind of polypeptide mixturefrom collagen or gelatin. It is widely used in food and cosmetic industries for its excellentpHysiochemical and functional properties. Nowadays there are still few studies reported onproducing and applying hydrolyzed gelatin. In our country, the collagen resource is severelywasted, thus causing environmental pollution. The main task of this subject is to study how toproduce the hydrolyzed gelatin and modify hydrolyzed gelatin through plastein reaction.First, the production of gelatin hydrolysates from bovine ossein with Alcalase was carefullystudied in this paper. Desalted ossein was cleaned several times with warm water, and milledwith grind wheel and colloid milling after adding two times volume water. The averageparticle of the slurry size is 158um. We chose the Alcalase in this research to study thehydrolysis condition. The results showed that the optimum hydrolysis conditions were:temperature 60 ℃ , pH9.5, the ratio of enzyme to substrate 1.5AU/kg, the substrateconcentration 4.4% and the time 3hr. The enzymatic reaction mechanism was also discussed.Various structures of the collagen were observed through scanning electric microscope (SEM).Molecular weight of the product was found to be about 788Da. From the result of amino acidanalysis we concluded that Gly was most, Glu less. Second, in order to expand the applying field of the hydrolyzed gelatin and investigate thecharacteristic of plastein reaction, we used methionine ester as modifier to modify thehydrolyzed gelatin through plastein reaction. This is a creation based on results of otherscientists in some way. Method of methionine ester synthesis reaction and product properties were studied in thiswork. We chose the DL-methionine lauryl as the modifier in the next study. DL-methioninereacting separately with different long chain was obtained. Results showed that various kindsof DL-methionine easter were obtained by ester reaction. The reaction conditions weremethionine: lauryl alcohol: p-toluenesulfonic acid:benzene = 1:5:1.1:22. These amino acidesters were recrystallized and the infrared spectrum analysis proved that DL-methioninen-alkyl esters were synthesized. Then products were separated by paper layer chromatogram.The result indicated that high purity esters were obtained. Results of methionine lauryl estersynthesis experiment showed that reaction time 24hr, benzene: methionine=11: 1(mol: mol),methionine: lauryl alcohol=1: 1(mol: mol), p-toluenesulfonic acid : methionine=1: 2(mol: mol)represented the optimal reaction conditions. Conditions of plastein reaction of methionineesters with hydrolyzed gelatin catalyzed by papain were studied.Statistical methods of single factor and princomp analysis were used in this paper. Theresults showed that productivity was the most important index, and then emulsify stability.The optimal reaction conditions were methionine dodecanol ester as substrate,temperature 55℃, pH6.0, the ratio of enzyme to substrate 0.1%, the substrate concentration 40% and thetime 6hr.Structures of plastein were analyzed via different methods in this study. The further resultsshowed that methionine lauryl ester joined successfully with hydrolyzed gelatin. Protein wasthe important component in plastein, and lauryl content was 1.7%. pI of plastein andhydrolyzed gelatin were 6.25 and 4.25 respectively. The average molecular weight of plasteinwas 956 Da. It mainly contained polypeptides of 233-2894 Da. Hydrogen bond, hydropHobicinteraction were mainly interactions in plastein. SEM pHotograpH indicated that jellyproduced during plastein reaction had compact space structure and was arranged orderly inregion.We have no last word on mechanism of plastein reaction till now, but its mechanism canprovide important theoretical bases in the application of plastein to food, cosmetic andchemistry industries. So we studied the mechanism of plastein reaction of hydrolyzed gelatinand methionine lauryl ester with papain. From effects of adding proteinase and ester or notand free terminal groups' content on plastein reaction, hydropHobicity and amino acidcomposition of plastein, we concluded that there were several processes in the plasteinreaction. These processes contained hydrolyzing, new peptide bond forming (transpeptide andpeptide condensation), pHysical aggregation (hydropHobic interaction, hydrogen bond,elecstatic interaction, etc.). Through these processes plastein jelly was formed.In addition, we studied rheology properties, thermodynamics properties, surface propertiesand water-solubility of the plastein in this paper. Results showed that the denaturalizingtemperature range of plastein became narrower and enthalpy variety was higher than that ofhydrolyzed gelatin. Viscosity of plastein solution became higher with higher concentration,but solution had good fluidity even if the concentration was 30%. Temperature had significanteffect on the viscosity, and the relativity accorded with Arrhenius model: lgη = lgA+Ea/2.303RT, that was lgη= 1.8978+11.5631/T. Plastein solution appeared to be a shearthinner liquid state when the shear rate was at lower range, but when the shear rate was above30 Pa.s, it became Newton liquid. Emulsify ability and stability of plastein solution becamehigher with higher concentration. Compared with hydrolyzed gelatin solution, plasteinsolution's emulsify ability descended, but emulsify stability ascend. pH and ion strength hadsignificant effect on plastein water-solubility, but temperature didn't...