Study On Preparation And Properties Of Polyglycerol Medium-Chain Fatty Acid Esters

Polyglyceryl fatty acid esters(PGFE)which are a new kind polyhydroxy ester nonionic surfactant of high efficient and excellent performance, are synthetized by polyglycerol and fatty acids.Polyglycerol medium-chain fatty acid esters are synthetized by polyglycerol and medium-chain fatty acids.Since the characters of good emulsibility,stability,dispersibility,defoaming,quality,improvement,oil crystallization adjustment and preventing protein denaturation,PGFE have been widely used in food, cosmetic, pharmaceutical industries, etc.They also can prevent the cohesion of the remaining fat to improve the expansibility and uniformity of the products,thus improving the taste of products.Therefore, developing medium-chain fatty acid esters as food emulsifiers and preservatives is promising.Polyglycerol was synthetized under the high temperature using NaOH as a catalyst.The result of MS showed that the product of polyglycerol has more polyglycerol with2to9degree of polymerization,which contained more cyclic polyglycerol.The hydroxyl value of polyglycerol was1048.25and the average degree of polymerization was4.35.Polyglycerol medium-chain fatty acid esters were synthetized by direct esterification. Acid value, saponification value, ester value and melting point were tested as the chemical and physical indexes of polyglycerol medium-chain fatty acid esters.Acid value, saponification value, ester value and HLB value and melting point of Polyglycerol Laurateare were1.3mgKOH/g,181.46mgKOH/g,180.16mgKOH/g,7.04,59.6℃respectively.Acid value, saponification value, ester value HLB value and melting point of Polyglycerol Caprate were1.52mgKOH/g,146.80mgKOH/g,145.28mgKOH/g,10.98,46.2℃respectively。Standing stability,centrifugal stability and thermal stability of emulsifying performance indexs were tested to evaluate emulsifying property of Polyglycerol Laurate and Polyglycerol Caprate when the oil/water ratio was1:1,and the minimum additive amounts of each index were the best were determined.The results showed that most of the emulsion types with low concentration of Polyglycerol Laurate and Polyglycerol Caprate are water in oil (O/W) type while the emulsion with high concentration of Polyglycerol Laurate and Polyglycerol Caprate are oil in water(O/W) type; the minimum additive amounts of each indexs of Polyglycerol Laurate are all2%,so the emulsion has the best indexes of emulsifying property when the amount of Polyglycerol Laurate was2%;the minimum additive amount of Polyglycerol Caprate for standing stability is3%, for centrifugate stability is4%, for thermal stability is4%and the emulsion has the best indexes of emulsifying property when the amount of Polyglycerol Caprate was4%.Polyglycerol Laurate has the better emulsifying property than Polyglycerol Caprate.The antimicrobial activity of Polyglycerol Caprate against food spoilage and foodborne pathogens were tested by the agar diffusion method and tube double dilution method.The minimum inhibition concentration(MIC) of Polyglycerol Laurate against fungi and bacteria are as follow:Escherichia Coli2.5mg/mL,Bacillus subtilis2.5mg/mL,Staphylococcus aureus0.32mg/mL,Aspergillus niger0.63mg/mL,Saccharomyces cerevisiae0.63mg/mL;The MBC of Polyglycerol Laurate against fungi and bacteria are as follow:Escherichia Coli10mg/mL, Bacillus subtilis10mg/mL, Staphylococcus aureus2.5mg/mL,Aspergillus niger1.25mg/mL,Saccharomyces cerevisiae2.5mg/mL;The minimum inhibition concentration(MIC) of Polyglycerol Caprate against fungi and bacteria are as follow: Escherichia Coli2.5mg/mL,Bacillus subtilis2.5mg/mL,Staphylococcus aureus0.32mg/mL,Aspergillus niger0.16mg/mL,Saccharomyces cerevisiae0.16mg/mL,Escherichia Coli5mg/mL,Bacillus subtilis5mg/mL,Staphylococcus aureus1.25mg/mL,Aspergillus niger0.32mg/mL, Saccharomyces cerevisiae0.63mg/mL.Polyglycerol Caprate has the better antimicrobial activity than Polyglycerol Laurate.In this paper, the antibacterial mechanism of Polyglycerol medium chain fatty acid esters was tested mainly from the cell membrane. The affection of Polyglycerol medium chain fatty acid esters to cellular membrane permeability was tested by conductance method. Coomassie brilliant blue colorimetric method and diphenylamine method were respectively to test the affection of Polyglycerol medium chain fatty acid esters to soluble protein content of culture medium and content of DNA.The results indicated that cellular membrane permeability increased at different degrees; protein and nucleic acid had leaked in varying degrees.