Research On The Synthesis Of Medium Chain Monoglyceride And Its Emulsifying And Antibacterial Activity

Medium Chain Monoglyceride (MCMG) which mainly include glycerol monocaprylate,1-decanoyl-rac-glycerol (MDG) and glycerol monolaurate (GML) have hydrophilic groups and hydrophobic groups, which make it an excellent emulsifier. MCTMG is a kind of broad-spectrum food preservative and can inhibit the growth of many common bacteria and fungal in food. In this paper, by esterification method to prepare MDG and GML, study the emulsifying and antibacterial activity on of MDG, GML and their mixture were studied. The results were as follows:The effect of the reaction time, temperature, catalyst amount and the mole ratio of glycerin to decanoic acid/laurel acid on the contents of MDG/GML were studied through single factor and response surface method(RSM).The results showed: the reaction time and temperature were the main factors; the mole ratio of glycerin to decanoic acid/laurel acid and catalyst amount were the secondary factors. The optimum synthesis parameters of MDG were:reaction temperature is 170.69℃, reaction time is 4.06 h, mole ratio is 3.53:1, catalyst amount is 0.5%, and the corresponding total MDG content is 89.24%. For GML, the optimum synthesis parameters were:reaction temperature is 160.61℃, reaction time is 3.06h, mole ratio is 2.52:1, catalyst amount is 0.4%, and the corresponding total GML content is 91.18%.The emulsifying activity of MDG, GML and their mixture were studied by adopted spectrophotometric method combining national standard GB/T11543-2008. The results showed that emulsification of MDG and the mixture was stable in the minimum adding dosage of 6%, in the optimal oil-water 3:7 ratio. And when the optimal ratio of oil and water was 4:6 and the minimum dosage of GML was 6%, the emulsifying activity was stable. Under the condition of the ratio of oil and water was 5:5,through centrifugation, standing, high temperature, cold-heat circulation processing, stability of different concentrations of MDG and GML and the mixture were determined. The results show that:the minimum adding amount of the mixture for centrifugal stability, static stability, heat stability and cold-heat cycle stability were 5%,3%,5%,4%. The minimum adding amount of GML for centrifugal stability, static stability, heat stability and cold-heat cycle stability were6%,5%,6%,6%.But MDG under this conditions only had the static stability. The results showed that emulsification of GML was superior to MDG, and the mixture of MDG and GML were better than a single MDG or GML.With the diameter of inhibition zone as index, the antibacterial activity of MDG, GML and the mixture were studied by the filter papers method. The minimum inhibition concentration(MIC) of MDG,GML and the mixture were determined by tube double dilution method. The results showed that MDG, GML and the mixture could inhibit the growth of some common bacteria and fungal in foods. The MIC of MDG was 2.5g/L for Escherichia coli,0.63g/L for S.aureus, Saccharomyces cervisiae and Aspergillus niger. The MIC of GML was 5g/L for Escherichia coli, 1.25g/L for S.aureus, Saccharomyces cervisiae and Aspergillus niger. The MIC of the mixture was 1.25g/L for Escherichia coli,0.32g/L for S.aureus, Saccharomyces cervisiae and Aspergillus niger.MCMG had weak inhibition on gram-negative Escherichia coli, but had better inhibition on Gram-positive bacteria, Staphylococcus aureus, yeast and Aspergillus niger. The inhibition activity of GML was weaker than MDG, and the inhibition activity of the mixture was superior to single GML or MDG. The MIC of MCMG inhibiting on Bacteria, mould and yeast were not changed with the pH from 4 to 8. That showed that MCMG had better acid and alkali stability inhibition activity.