| Previous research of our research group showed that under the condition of ultra-high pressure,lotus seed amylose and fatty acids with different chain lengths and saturation degrees form V-type complex with good thermal stability and anti-digestion characteristics,which provides a theoretical basis for the combination of starch and lipid.However,the tight arrangement of lotus seed starch results in the difficulties of depolymerization,and for lipid entry,therefore affecting the embedding effect of the complex to a certain extent.If lotus seed starch can be modified properly to enhance the interaction between starch and lipids,the composite effect can be improved.Conjugated linoleic acid?CLA?is an essential fatty acid for human body,which can effectively improve the intestinal flora.However,the structure of CLA is not stable and it is easy to be oxidized under a high temperature.Therefore,octenyl succinate?OSA?was used to modify lotus seed starch in this paper.On this basis,the non thermal processing technology and ultra-high pressure were used to prepare OSA modified lotus seed starch conjugated linoleic acid complex,and the physical and chemical properties,structural properties,thermal properties and anti digestion properties of the complex were studied.This study is beneficial to expand the application of non thermal processing technology in the fields of starch modification and starch to CLA embedding.The main conclusions are as follows:?1?Study on the modification and structural characteristics of lotus seed starch octenylsuccinic acidIn order to enhance the complex effect between lotus seed starch and conjugated linoleic acid,lotus seed starch was esterified with different amounts of octenylsuccinic anhydride?OSA??3%,5%,7%,9%??35?,3 h?,and the degree of substitution?DS?,particle characteristics and aggregation structure of lotus seed starch esters were studied.The results showed that when the concentration of OSA increased from 3%to 9%,the degree of substitution increased from 0.0148 to 0.0389.The results of SEM showed that the esterification of OSA could destroy the morphology of lotus seed starch,and the degree of damage was in direct proportion to the concentration of OSA.There are two new absorption peaks at 1526cm-1 and 1728 cm-1 in FTIR spectrum analysis.1526 cm-1 and 1728 cm-1are characteristic absorption peaks generated by-COO-and C=O,respectively,indicating that lotus seed starch is successfully esterified.The particle size of lotus seed starch increased significantly after esterification?P<0.05?,and the particle size of lotus seed starch ester increased gradually with the increase of the content of OSA.When the content of OSA was 9%,the D?10?of lotus seed starch ester increased from 1.71±0.07?m to 15.4±0.70?m,and D?50?from 10.7±1.01?m to387±15.09?m and D?90?increased from 16.8±0.78?m to 491±3.00?m.After esterification of starch with OSA,the Mw,Mn and Mw/Mn of amylose decreased slightly.The results of X-ray diffraction showed that the esterification of OSA did not change the crystal form of lotus seed starch,but the crystallinity decreased to some extent.In conclusion,compared with lotus seed starch,octenylsuccinate lotus seed starch is easier to spin and form a hydrophobic spiral cavity,which provides a basis for the combination of lotus seed starch and conjugated linoleic acid.?2?Study on the preparation and structural properties of OSA modified lotus seed starch conjugated linoleic acid complexOn the basis of OSA modification of lotus seed starch,the complex of lotus seed starch conjugated linoleic acid?CLA/LS?OSA-Starch?=1:2,1:3,1:4?was prepared by ultra-high pressure treatment?600 MPa,30min?.The composite index,particle characteristics and aggregation structure of the complex were studied.The results of X-ray diffraction showed that the crystal structure of OSA modified lotus seed starch conjugated linoleic acid complex was still C-type,which was consistent with the original starch,but the crystallinity was significantly increased,up to 42.73%.The results showed that the super-high pressure treatment could destroy the hydrophilicity of the OSA modified lotus seed starch conjugated linoleic acid complex and increase the particle size of the complex.Due to the introduction of macromolecular conjugated linoleic acid,the molecular weight of OSA modified lotus seed starch conjugated linoleic acid complex increased,which also indicated that the structure of the complex was stable.The results of scanning electron microscopy showed that there were cracks and collapses on the surface of lotus seed starch conjugated linoleic acid composite particles.The laser confocal scanner further observed the internal structure of the composite particles,which showed that the distribution of conjugated linoleic acid was both inside and outside the composite particles.?3?Study on the thermodynamic properties of OSA modified lotus seed starch conjugated linoleic acid complexBased on the study of the structure and properties of the complex,the thermodynamic properties of the complex were further studied.The results of solubility and swelling power showed that the solubility of the complex increased with the increase of temperature,and increased significantly at 75?.When the temperature is lower than 75?,the solubility and swelling power of the composite prepared by UHP are the largest.When the temperature is higher than 75?,the solubility and swelling power of the composite prepared by UHP are lower than that of the control group.DSC results showed that the thermal stability of the conjugated linoleic acid starch conjugated linoleic acid complex was better when the ratio of conjugated linoleic acid was 1:2?conjugated linoleic acid/lotus seed starch?.There was no significant difference in the values of To,Tp and Tc,which indicated that the presence of conjugated linoleic acid had little effect on the thermodynamic properties of lotus seed starch.The results of TGA showed that the weight loss of each group increased with the increase of temperature.According to the different temperature,the mass loss is divided into two stages,25-200?is the first stage of mass loss,and 200-350?is the second stage.In the first stage,the loss of quality is mainly due to the evaporation of water in starch,while in the second stage,the loss of quality is due to the destruction of carbonyl structure?C=C?in Starch Chain and the degradation of starch chain.In the first and second stages,the mass loss of the composite prepared by UHP was less than that of lotus seed starch,which indicated that the crystal structure of lotus seed starch conjugated linoleic acid could improve the thermal stability of the composite.?4?Study on the anti-digestion properties of OSA modified lotus seed starch conjugated linoleic acid complexConjugated linoleic acid can effectively improve the colon micro ecological environment.In order to maximize the biological activity of conjugated linoleic acid,OSA modified lotus seed starch conjugated linoleic acid complex should be difficult to be digested in the stomach and small intestine,and only be decomposed by microorganisms in the colon.In this chapter,the dynamic in vitro rat stomach duodenum?DIVRSD-??model was used to simulate the in vitro digestion process of the complex and explore the anti digestion performance of the complex.Results showed that the digestibility of OSA modified lotus seed starch conjugated linoleic acid complex was the lowest in the whole digestion process?0-180 min?,and the digestibility of the complex was higher than that of other samples after 120 min,indicating that the formation of the complex increased the content of resistant starch in the starch.The formation of conjugated linoleic acid complex?1:2,conjugated linoleic acid/lotus seed starch?significantly reduced the digestion rate of lotus seed starch,which was about 27%lower than the original lotus seed starch.The results of scanning electron microscopy and laser confocal observation showed that the surface of the hydrolysate?180 min?of OSA modified lotus seed starch conjugated linoleic acid complex was smooth and the structure was compact,and the fluorescence intensity was the strongest in the laser confocal image,which indicated that the OSA modified lotus seed starch conjugated linoleic acid complex prepared by ultra-high pressure had strong anti-digestion effect. |
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