| Pectin is a common and important natural polysaccharide,it’s application in industry has been limited due to the strong hydrophilic,in order to enable it to meet the industrial application,so we have to adjust its performance by chemical modification.A large number of studies have shown that there are many chemical modification methods including esterification,alkylation,amidation,thiolation,sulfation,and oxidation,etc.However,the research of use lipase to catalyze pectin modification was rarely reported.Therefore,this project studied lipase RMIM used as catalyst,pectin and middle fatty acids in Cinnamomum camphora seed oil as the substrate of the esterification reaction,the carbon chain of middle fatty acids were introduced into pectin molecule,its degree of substitution was determined by GC to optimize the best synthetic conditions;FTIR and 1H NMR were used to characterize the modified pectin.The properties of emulsion and rheological of products were studied;Used pectin and its derivatives as emulsifier to prepared silymarin microemulsion and determined its release in vitro;Effectiveness of pectin and its derivatives cotaing in improving shelf-life of eggs and studied the inhibitory effect of two kinds of food-borne bacteria(escherichia coli,staphylococcus aureus).The obtained results are as follows:1.Using single factor optimization method to optimize the best reaction conditions of pectin and Cinnamomum camphora seed oil were the reaction temperature 60 ℃,pectin-camphor tree seed oil quality ratio of 1:2,lipase adding amount of 15% w/w,response time is 24 h,modified pectin are obtained by GC determination of degree of substitution(62.40±0.01)%.2.The chemical structure of pectin and its derivatives was characterizaed by FTIR,it can be proved that the hydroxyl of pectin had occured esterification reaction with the carboxyl of middle fatty acids in CCSO.FTIR result indicated that compared to the pristine pectin,a decrease of the O-H stretching bands observed.Major because that the carboxy group of the fatty acids were reaction with the hydroxyl of pectin.On the other hand,it was obvious that the increase of C-H stretching band indicated thatpectin was combined of new C-H moieties in the introduced fatty acids.The region featuring the state of carboxylic groups(1750–1350 cm-1)is the most interesting.As showed in FI-IR spectrum of the pectin,there three peaks at 1751,1629,1446 cm-1 in the carboxylic groups region assigned to the C=O stretching of methylated carboxyl groups,and to anti-symmetric and symmetric stretching modes of COO-,respectively.Other changes are registered in the “fingerprint region”,the intensity of the band1102 and 1019 cm-1 which were assigned to the C-O and C-C,were increased with the degree of substitution.The 850–600 cm-1 region contains new bands which are related to the introduced fatty acid chains.Nuclear magnetic spectrum results show that comparison of the original pe ctin,the spectrum of pectin ester has appeared some new absorption peak am ong 1.0-2.0ppm,except the characteristic peak of original pectin at the spectra of modified pectin.Among them,the absorption peak atδ1.13 came from the CH2 group of middle chain fatty acids,the absorption peak atδ1.34 came from the CH2CH2 COO group of middle chain fatty acids and the absorption peak a tδ1.94 came from the CH2 COO group of middle chain fatty acids,thus indicat ed that carbon chain of middle fatty acids were introduced into the molecular structure of pectin.3.Emulsion and rheological properties were studied,the results showed that the Emulsion Capacity(EC)of pristine pectin at the concentration of 0.5% was 43.70%.At the concentration of 0.3%,1.0%,1.5%,2.0% they EC were(40.51±1.20)%,(58.24±1.66)%,(72.63±1.20)% and(85.29±3.85)% respectively.After esterification,the EC of emulsion was strengthened and increased with the increasing of pectin’s concentration.For the concentration were 0.3%,0.5%,1.0% and 1.5%,the EC of pectin derivatives were(46.25±1.02)%,(52.57±0.05)%,(77.27±1.83)% and(87.01±0.41)%,respectively.Moreover,the emulsion stability of modified pectin was better than the pristine pectin.When the concentration of pectin at 0.3% and0.5%,no emulsion layer was observed on this two sample after storage and centrifugation.And when the concentration increased to 1.0%,1.5% and 2.0%,the ES of the pristine pectin were(42.10±2.56)%,(75.23±1.53)%,(90.04±2.59)% after 7days of storage.But,the ES of pectin derivatives were different.Their ES were(7.62±0.23)% and(12.32±1.61)%,(69.05±1.55)% and(96.67±0.39)%,respectively,at the concentration of 0.3%,0.5%,1.0% and 1.5% after 7days of storage.Also,the viscosity of pectin derivatives was higher than original pectin,it maybe because the carbon chain of middle fatty acids were introduced into pectin.4.Using pectin and its derivatives as emulsifier to prepared silymarin microemulsion and determined its release in vitro,the results showed that choose 1,2-propylene glycol as co-emulsifier,camphor tree seed oil as oil phase.Mixed emulsifier that pectin/pectin with 1,2-propylene glycol ester is 2:1,silymarin-oil phase-mixed emulsifier is 0.5:1:8.5 the preparation of two kinds of microemulsion(pectin/pectin ester),to determine the content of saturated silymarin,particle size and zeta potential were(53.84±0.80),(56.89±1.30)mg/mL,(502.67±14.63),(462.67±14.63)nm and(-45.3±0.10)mV,(-46.8±0.30).In vitro release results show that the release effects of two kinds of homemade microemulsion stronger than legalon,including the release of pectin ester microemulsion effect is best,the cumulative release rate of 12 h(55.8±2.67)%,pectin microemulsion 12 h release rate was(46.67±1.71)%,and the liver lung release rate into only for 12 h(32.28±0.20)%,so these two kinds of homemade microemulsion has a certain effect of in vitro release.Therefore,the use of modified pectin preparation of microemulsion is such effect is good.5.Coating preservation method was used to study of pectin and its derivatives extend the life of the eggs,the results showed that pectin and its derivatives(especially PE+LA)had good preservation effect,can effectively control the change of sensory and physicochemical index of eggs during storage time,inhibit the growth of bacteria,thus extend the life of eggs and freshness.The research of the inhibition effect of two food-borne bacteria(escherichia coli,staphylococcus aureus)of pectin and its derivatives,the results showed that when the concentration of pectin in 5 mg/m L,its inhibition on E.Coli only 2.71%,low for staphylococcus aureus antibacterial rate reached 39.08%,and when its concentration reaches 10 mg/m L for the two kinds of bacteria inhibition rate was 15.43%,45.28%,respectively.However,compared to pectin,the effect of inhibition of pectin ester is better.When the concentration of pectin ester solution respectively in 5 mg/mL,10mg/mL,the inhibition rate of e.coli were 19.32%,45.94%,inhibition of s.aureus were 51.62%,63.13%,this is obviously higher than that of pectin,shows that after modification of pectin has better antibacterial activity. |
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