Research On The Preparation And Antimicrobial Activity Of Glycerol Monocaprate

Monoglycerides,especially medium-chain monoglycerides are of good emulsifying ability and antibacterial effect on bacteria,yeast and mould,contributing to the application in food,medicine and cosmetic industry.Presently,the monoglycerides are synthezed by transesterification method with heterogeneous catalyst despite the disadvantage of synthesis method including low speed,high reaction temperature,low yield and easy saponification.The monoglycerides prepared after separation and purification by chemical methods were of low purity,inefficiency and toxic solvent residue,which caused the limit in the field of food,medicine and drugs.At present,preparation methods,physicochemical properties and antibacterial activity of glycerol monocaprate are little reported,and chemical preservatives is poisonous to human body in general Additionally,the prepared glycerol monocaprate with high purity is important to explore noverty,efficient,safe and.health preservative in food industry due to the harm of chemical preservative with poision to human health.In this study,the process optimization of GMC based on single-factor experiment and response surface methods using concentrated sulfuric acid as catalyst was set.The purity of GMC purified using crystallization,column chromatography and molecular distillation were measured.Using X-ray diffraction(XRD),polarized lightmicroscopy(PLM),differential scanning calorimetry(DSC),nuclear magnetic resonance(NMR)spectrophotometry,inverted microscope and thermogravimetric-differential thermal analysis(TG-DTA),the physicochemical property including crystal structure,microstructure of crystallization,isothermal crystallization,melting characteristics,solid fat content(SFC),emulsification ability,emulsion microstructure and thermal stability were determined repectively.Using 7 kinds of common food spoilage organisms(bacteria,yeast and mould)as indicator bacteria of bacteriostatic experiment,the minimal inhibitory concentrations(MIC)of GMC were determined and the effect of pH value on MIC by gar dilution method.Meanwhile,use liquid culture method to determine the minimum bactericidal concentration(MBC)using potassium sorbate and sodium nitrite positive control as positive control.1.The optimal conditions was as follows:the mole ratio of glycerinum to capric acid,2.5:1;reaction temperaure,132?;the amount of catalyst,2%;reacton time,2.5 h.Effect order of GMC content were amount of catalyst,reaction temperature,reaction time and mole ratio,repectively.In this case,the content of GMC was approximately 52%.2.According to the separation and purification results,using crystallization,column chromatography and two-level molecular distillation methods,the purity of GMC were 70.35%,85.09%and 95.80%,respectively.The accuquired rate of high purity GMC was 45.3%.Besides,the optimal conditions were as follows:I level molecular distillation to remove capric acid,feeding rate was 250 g/h;rotor speed,300 rad/min;condensing temperature,45?;distillation temperature,110 ?;system residual pressure,20 Pa.II level e molecular distillation to remove diacylglycerol and triacylglycerol,feeding rate was 250 g/h;rotor speed,300 rad/min;condensing temperature,45 ?;distillation temperature,150 ?;system residual pressure,10 Pa.3.According to the physicochemical properties results,GMC presented white powder,with its melting point ranging 48-55 ? and refractive index being 1.464 at room temperature.GMC with polymorphism produced three kinds crystal texture namely ?,?'and ? at room temperature,and ?' was the most.Additionally,crystal particle at room temperature with foliated form was bigger than that at low temperature.In the crystallization process of GMC,with the increaseing cooling rate,the summit of three crystal peak tended to left shift slightly.In the melting process,at the heating rate of 5,10,15?/min,the only peak temperayure of GMC were 48.43,49.21,and 48.43 ?,respectively.GMC was of plasticity at 25?(room temperature)and the solid fat(SFC)was 77.70%.GMC was of emulsifying property,and presented the distribution regularity of emulsion particles;its emulsifying ability was the strongest at water-oil ratio 4:6.At 4%the emulsion particle size were basically the same with the uniform distribution.Thermal stability of GMC was very good below 170??4.According to the results of the microorganism(bacterial,yeast and mould)activity of GMC,GMC had antimicroorganism effects on bacterial,yeast and mould.The MICs on escherichia coli,staphylococcus aureus,bacillus subtilis,bacillus cereus,saccharomycetes,aspergillus niger and aspergillus oryzae were 0.16,0.08,0.04,0.16,0.64,0.32 and 0.64 mg/mL,respectively,independent of pH.Accordingly,the MBCs were 2.5,0.63,0.63,2.5,1.25,2.5,5 mg/mL.Moreover,the MICs and MBCs of GMC on microorganism were lower than that of potassium sorbate and sodium nitrite,and antimicroorganism effects of GMC were more excellent than that of potassium sorbate and sodium nitrite.