The Enzymatic Synthesis And Functional Properties Of Sugar Esters

Firstly,the foaming and emulsifying properties of a range of sucrose stearates were studied by measuring the content of monoester,diester,polyester as well as their hydrophile-lipophile balance（HLB）values.The composition and functional properties relationship has been revealed.Results showed that the HLB values were mainly determined by the content of sucrose stearate monoester,a significant correlation was observed.As the lower HLB values as well as content of sucrose stearate monoester usually resulted in decreased foaming ability,foam stability and emulsion stability of the series of sucrose stearate,however,the emulsifying ability was observed to increase prior to decrease in this process.Meanwhile,an enzymatic synthesis of mono-sucrose stearate was completed,in a regio-selective fashion by using sucrose and stearic acid ethyl ester as the substrates,in the presence of phase transfer catalyst（myristyltrimethylammonium bromide）.The physico-chemical properties of the associate product were measured.The structure of mono-sucrose stearate synthesized by this work has been confirmed by ¹H-NMR,¹³C-NMR and ESI-MS with a HLB value 14.90,its foaming ability,foam stability and emulsifying ability as well as emulsion stability were also evaluated.Secondly,silica gel column chromatography was applied to purify and the structure of sucrose stearate separated by this work have been confirmed by IR,¹H-NMR,¹³C-NMR and ESI-MS.Furthermore,the HLB value,solubility in different solvents as well as thermogravimetric analysis were evaluated.Results showed that the products were 6-O-sucrose stearate,6′-O-sucrose stearate and 6,6′-O-sucrose stearate.The optimum conditions for silica gel column chromatography were:1.74 g sample dissolved in mixed solvents of methanol and methylene chloride,the products were separated with silica gel column chromatography by elution gradient of mobile phase.The 6-O-sucrose stearate and 6′-O-sucrose stearate showed similar HLB value,solubility in different solvents and thermal stability,The HLB value of 6,6′-O-sucrose stearate was 11.44,however,the dissolution was secondary and the initial loss rate was higher.Ultimately,an enzymatic synthesis of mono-maltose ester was completed,in a regio-selective method by using maltose and fatty acid ethyl ester as the substrates.The physico-chemical properties of the associate product were measured.Results showed As the chain length of the fatty acid increased resulted in the HLB value,foamability as well as emulsifying ability were observed to increase prior to decrease and revealed a surprising inverted V-type profile,but the thermal stability was decreased with increase of carbon chain length.Myristoylmaltose reduced particle size distribution can thus lower the probability of coalescence of the droplets,which resulted in a better emulsion stability.Furthermore,Sugar esters was synthesized by the acylation of glucose,maltose,malt-trisaccharide with vinyl palmitic using immobilized lipase in organic phase.The change rule of functional properties of monosaccharide-,disaccharide-and tri-saccharide-monopalmitate was revealed with the HLB value,thermogravimetric analysis,foaming as well as emulsifying properties were measured.Results showed that the solubility in water,the HLB values were mainly determined by the molecular weight of hydrophilic moieties.Note that between glucose-,maltose-,malt trisaccharide-palmitate monoester,maltose palmitate monoester was stabilizated to heat.However,the foaming and emulsifying properties of malt trisaccharide-palmitate monoester were better than others.