Study On Emulsifying Property And Antibacterial Properties Of 1-decanoyl-rac-glycerol

1-decanoyl-rac-glycerol(MDG)is a new kind nonionic surfactant with high efficience and excellent performance.As one kind of excellent food emulsifier,MDG has been widely used in cosmetic,food and pharmaceutical industries,etc.MDG has excellent emulsibility,stability,defoaming and dispersibility,can prevent protein denaturation,improve the quality and flavor of food.What's more,MDG is a kind of broad-spectrum food preservative which can inhibit the growth of some bacteria and fungi in food.This paper mainly studies the emulsifying,antibacterial activity and antibacterial mechanism of MDG.Single factor experiment(the mole ratio of glycerin to decanoic acid,reaction temperature,reaction time,catalyst amount)and orthogonal experiment have been used to study the effect of experimental factors and conditions on the content of MDG.The result shows the mole ratio of glycerin to decanoic acid is the most important factor,followed by reaction time,reaction temperature,and catalyst amount,and the optimum synthesis parameters are:reaction temperature is 180?,mole ratio is 4:1,reaction time is 6h,catalyst amount is 0.6%,and the content of MDG is 82.3%.After molecular distillation,the content of MDG is 96%.The emulsifying activity of MDG has been studied under different ratio of oil and water.After standing,high temperature handling and centrifugation,the stability of MDG with different concentrations are tested.The result shows that the emulsification of MDG stays stable when the oil-water ratio is 4:6,with 5%minimum additive amount,and the minimum additive amounts of MDG for standing stability,centrifugate stability and heat stability under oil-water ratio 1:1 are 6%,6%,8%.By the agar diffusion method,measuring the diameter of inhibition zoo as index,and the tube double dilution method,the antimicrobial activity,minimum inhibition concentration(MIC),and minimum bactericidal concentration(MBC)of MDG are tested with Staphylococus aureus,Bacillus subtilis,Escherichia Coli,Aspergillus niger,Saccharomyces as indicator bacteria.The result shows that MDG can inhibit the growth of some food bacteria and fungi,and the MIC and MBC of MDG against the indicator bacteria are as follows:Staphylococus aureus 0.08g/L,0.32g/L,Bacillus subtilis 0.08g/L,0.32g/L,Escherichia Coli lOg/L,40g/L,Aspergillus niger 0.32g/L,2g/L,Saccharomyces 0.32g/L,1g/L.The antibacterical aging of MDG against bacteria and yeast are tested by the adopted spectrophotometric method,while mycellum dry weight method to test the antibacterical aging of MDG against mildew.The result is:the antibacterial rate of MDG keeps for 100%,for Staphylococus aureus,Bacillus subtilis,Escherichia Coli are 60h,75h,and 20h;for Saccharomyces and Aspergillus niger a 45h and 3 0h,and for fungi,the bacteriostasis half-life MDG for Saccharomyces and Aspergillus niger are 105h and 95h.The antimicrobial activity of MDG for gram-positive bacteria and fungi is better than MDG for gram-negative bacteria.The antibacterial mechanism of MDG was studied from cell membrane level.The affection of MDG to cellular membrane permeability is tested by conductance method,while the affection of MDG to the content of soluble protein and DNA are tested by Coomassie brilliant blue colorimetric method and diphenylamine method.The final result shows that MDG can change the cellular membrane permeability and make the soluble protein and nucleic acid leaked at different degrees.