【作者】 高伟；

【导师】 崔波；

【作者基本信息】 山东农业大学 ， 食品科学与工程， 2021， 博士

【摘要】 辛烯基琥珀酸淀粉酯（OS淀粉）是淀粉与辛烯基琥珀酸酐（OSA）经酯化反应而得,因其优良的乳化性能和安全性成为国内外研究的热点。然而在其传统改性制备过程中,OSA在水中溶解度较低且OSA官能基团在淀粉颗粒内部分布不均匀导致反应效率低下、产品性能较差。因此,对淀粉颗粒进行适当的预处理以增加OSA进入淀粉颗粒内部的有效路径进而实现酯化反应的充分进行是十分必要的。本研究以淀粉颗粒结构为切入点,采用不同温度（83℃、76℃和69℃）对2%淀粉悬浮液（w/w）进行预处理并回收,定义为不同水热预处理玉米淀粉（C_s）,研究了其结构和性能的变化,并基于此进一步探讨了OSA与C_s的反应规律,结果表明不同水热预处理提高了OS淀粉的取代度（DS）,实现了OSA与C_s的充分反应。此外,采用二甲基氯硅烷（TDMS-Cl）对淀粉葡萄糖结构单元（AGU）碳2、6位羟基进行保护预处理,初步实现了碳3位OS淀粉（C-3-OS淀粉）的合成,旨在拓展与创新OS淀粉合成方法。最后,采用油包水（W/O）反相微乳液工艺制备了玉米淀粉（CS）、辛烯基琥珀酸酐酯化玉米淀粉（OSCS）和不同水热预处理辛烯基琥珀酸酐酯化玉米淀粉（OSC_s）微凝胶并用于包封表没食子儿茶素没食子酸酯（EGCG）以研究其缓释应用特性;采用OSC_s-83为乳化剂,制备了不同大豆油含量的玉米淀粉/OS淀粉复合膜并研究了其相关性能。主要结果如下:1.不同水热预处理对玉米淀粉的分子结构和理化性能有显著影响。CS和不同水热预处理玉米淀粉（C_s-83、C_s-76和C_s-69）均包括支链淀粉、中间级分和直链淀粉3种组分,其相对分子量（M_w）介于4.11×10⁷～11.42×10⁷ g/mol。直链淀粉含量顺序依次为:C_s-83>CS>C_s-69>C_s-76。CS与C_s-83的动态模量、表观粘度、峰值黏度和最终黏度并无显著差异,而C_s-69和C_s-76则呈下降趋势。CS、C_s-69、C_s-76和C_s-83的开始热降解温度分别为312.26℃、311.87℃、307.62℃和307.11℃。经不同水热预处理后,淀粉的晶型由A型转变为C型,C_s的相对结晶度低于CS（26.87%）。红外光谱（FTIR）结果表明,C_s分子内和分子间氢键作用减弱。2.不同水热预处理显著影响OS淀粉的结构。FTIR结果显示OSCS和OSC_s在1720 cm^-1和1570 cm^-1附近出现了两个新的特征峰,其分别对应酯羰基（C=O）和羧基（RCOO^-）的不对称伸缩振动,并且OSC_s特征峰强度大于OSCS。OSCS、OSC_s-83、OSC_s-76和OSC_s-69的DS值分别为0.0121、0.0170、0.0128和0.0140。随着DS值的增大,OSCS和OSC_s的直链淀粉含量增加而M_w减小。此外,X射线光电子能谱（XPS）和激光共聚焦显微镜（CLSM）结果显示OSC_s具有较小的表面DS值和较强的荧光强度,这表明不同水热预处理促进了OSA官能基团在淀粉颗粒内部的均匀分布。3.不同水热预处理对OS淀粉的理化性能有显著影响。随着DS值的升高,OSC_s颗粒形状不规则且表面呈现明显粗糙。OSC_s糊的PV值（1761.3～4251.0 c P）显著（P<0.05）高于OSCS（1031.3 c P）。OS淀粉糊呈现剪切变稀的特性,其表观粘度变化趋势与DS值一致,大小顺序如下所示:OSC_s-83>OSC_s-69>OSC_s-76>OSCS。OSC_s糊具有弱凝胶结构特性,其凝胶抗拉强度高于OSCS。不同水热预处理降低了OSC_s的热稳定性,OSCS、OSC_s-83、OSC_s-76和OSC_s-69的最大热降解温度(T_max)分别为319.76℃、306.52℃、306.56℃和308.10℃。不同水热预处理破坏了淀粉颗粒结晶结构,导致无定形区域增加,促进水分子进入淀粉颗粒内部,这有助于提高OS淀粉的溶胀性能和透明度。经不同水热预处理后,OSC_s的抗性淀粉（RS）含量增加（37.90%→45.33%）,快消化淀粉（RDS）含量降低（50.96%→45.23%）。4.定向合成了C-3-OS淀粉。FTIR结果显示,2,6-TDMS淀粉和C-3-OS-2,6-TDMS淀粉在1253 cm^-1、833 cm^-1和776 cm^-1处出现了三个与TDMS-Cl的C-Si拉伸有关的特征峰,而在C-3-OS淀粉的FTIR图谱中,这三个特征峰消失。C-3-OS淀粉的¹³C-NMR谱显示,在100 ppm处仅观察到一个信号峰,其对应于AGU邻近2位羟基的C1,这表明AGU的C2位置没有被取代。同样,C-3-OS淀粉的¹³C-NMR谱在60 ppm的信号与CS相比,其强度也没有变化,表明C6位置也没有被取代。而在80 ppm处,C-3-OS淀粉的未取代位置C3的信号比CS的信号低,这意味着AGU的C3位置发生了取代反应。5.采用W/O反相微乳液工艺制备并表征负载EGCG的CS、OSCS和OSC_s微凝胶。在W/O体系中,OSC_s分子之间形成了较强的氢键。OSC_s微凝胶的平均粒径较小,热稳定性差,形状不规则,呈典型的V型晶体结构。EGCG被OSCS和OSC_s微凝胶吸附后,EGCG的羟基与OSCS和OSC_s微凝胶的氧原子之间形成了较强的相互作用,包封率（EE）为41.78～63.89%,对1,1-二苯基-2-苦肼基（DPPH）的清除率为75.53～85.37%,均高于CS微凝胶。负载EGCG的OSC_s微凝胶呈现较明显的缓释特性,EGCG累计释放量变化较小,且低于负载EGCG的CS和OSCS微凝胶。因此,OSC_s微凝胶在负载多酚类物质方面具有潜在的应用前景。6.制备了不同大豆油含量的玉米淀粉/OS淀粉复合膜并对其表征。选取DS值最大的OSC_s-83作为乳化剂,制备了不同大豆油含量的玉米淀粉/OS淀粉复合膜。一定浓度的大豆油（<2%）可促进淀粉分子间的相互作用和氢键的形成。不同大豆油含量的玉米淀粉/OS淀粉复合膜均呈现相似的X射线衍射（XRD）图样和较低的相对结晶度。扫描电镜（SEM）和原子力显微镜（AFM）结果显示随着大豆油添加量的增加（0～2%）,淀粉膜表面出现不规则和粗糙的结构,平均粗糙度（Ra）从12.2nm增大到41.7 nm。当大豆油含量为1.5%时,玉米淀粉/OS淀粉复合膜的水接触角（CA）最大而水蒸气透过率（WVP）最小,分别为76.14°和2.46×10^-12g·cm/cm²·s·Pa。当大豆油含量为1.0%时,玉米淀粉/OS淀粉复合膜的抗拉强度最高,为6.54 MPa。当大豆油含量为1.5%时,玉米淀粉/OS淀粉复合膜的断裂伸长率最高,为71.84%。更多还原

【Abstract】 Globally,there is an increasing interest in the research of octenyl succinylated starch（OS starch）（obtained by esterification of starch and octenylsuccinic anhydride（OSA））due to its excellent emulsifying and safety properties.However,the low solubility in water and the uneven distribution of OSA groups within starch particles lead to poor reaction efficiency and product performance.Therefore,it is necessitated pretreatment of starch granules to increase the effective path of OSA within starch particles to realize the full esterification reaction.With starch granule structure as the breakthrough point,starch particles were pretreated and recovered at different temperatures（83,76,and 69oC）to evaluate changes of their structure and properties in this study.Based on that,the reaction rule of OSA with C_s was further discussed.The results showed that different hydrothermal pretreatments improved the degree of substitution（DS）of OS starch,and realized the full reaction between OSA and starch granules.In addition,a new synthetic method of C-3 octenyl succinic anhydride-modified corn starch（C-3-OS starch）assisted by thexyldimethyl chlorosilane（TDMS-Cl）was designed for directional modification of starch.Moreover,corn starch（CS）,octenyl succinic anhydride modified corn starch（OSCS）,and octenyl succinic anhydride modified corn starch pretreated at different hydrothermal pretreatments（OSC_s）microgels were prepared via water-in-oil（W/O）inverse microemulsions for loading and releasing of epigallocatechin gallate（EGCG）.CS/OS starch composite films incorporated with soybean oil at 0,0.5%,1.0%,1.5%,and2.0%（w/w）were prepared to investigate their physicochemical properties.The main results of our work are stated as following:1.The physicochemical properties of CS were significantly affected by different hydrothermal pretreatments.Both CS and C_s contained three components（amylopectin,intermediate fraction,and amylose）with M_w ranging from 4.11×10⁷ to 11.42×10⁷ g·mol^-1.The amylose content of CS and C_s was in the following order:C_s-83>CS>C_s-69>C_s-76.There were no significant differences between CS and C_s-83 for dynamic modulus,apparent viscosity,peak viscosity,and final viscosity,while C_s-69 and C_s-76 displayed a decreasing trend.There was an obvious decrease in the thermal degradation onset temperature（T_o）for treated samples（CS:312.26℃,C_s-69:311.87℃,C_s-76:307.62℃,and C_s-83:307.11℃）.The crystalline patterns of CS were converted from A-type to C-type during different hydrothermal pretreatment processes.The relative crystallinity of C_s was significantly lower than that of CS（26.87%）.The FTIR results showed a weak intramolecular and intermolecular hydrogen-bonding（O-H）of C_s.2.OS starches（OSCS,OSC_s-83,OSC_s-76,and OSC_s-69）were prepared based on different hydrothermal pretreatments.High intensity peaks around 1720 cm^-1and 1570 cm^-1 were observed for OSC_s in FTIR spectra.The DS values of OSCS,OSC_s-83,OSC_s-76,and OSC_s-69 were 0.0121,0.0170,0.0128,and 0.0140,respectively.The average molecular weight（M_w）of OSA modified CS decreased,due to the introduction of OS groups.Meanwhile,lower surface DS and higher fluorescence intensity were noticed for OSC_s.Conclusively,different hydrothermal pretreatments would promote the uniform distribution of OSA functional groups within starch granules.3.The properties of OS starch were affected by different hydrothermal pretreatments.OSC_sshowed pronounced surface depression with increasing DS values.OSC_sshowed a higher PV（ranging from 1761.3 to 4251.0 c P）than OSCS（1031.3 c P）.A reduction in the apparent viscosity with increases in shear rates for all starch pastes denote that starch dispersion showed a shear-thinning behavior.The apparent viscosity at a fixed shear rate was in the order of OSC_s-83>OSC_s-69>OSC_s-76>OSCS>CS.OSC_s starch gels had greater tensile strength than OSCS.T_maxof OSCS,OSC_s-83,OSC_s-76,and OSC_s-69 were 319.76℃,306.52℃,306.56℃,and 308.10℃,respectively.Different hydrothermal pretreatments damage starch granules and result in increases of amorphous region that lead to high swelling power and transparency of OSA derivatives.An increase in RS content（37.90%→45.33%）and a decrease in RDS content（50.96%→45.23%）were recorded for OSC_s.4.A new synthetic method of C-3 octenyl succinic anhydride-modified corn starch（C-3-OS starch）was designed.There were three characteristic peaks appearing at 1253,833,and 776 cm^-1 for 2,6-di-O-TDMS starch and C-3-OS-2,6-di-O-TDMS starch,which were associated with C-Si stretching of TDMS-Cl.Further,when C-3-OS-2,6-di-O-TDMS starch was deprotected by TBAF to generate C-3-OS starch,the characteristic peaks at 1253,833,and 776 cm^-1 practically disappear.Only one signal at approximately 100 ppm assigned to C-1 of the AGU neighbouring position 2 bearing a hydroxyl group was observed,the finding which denotes that position C2 of the AGU was not functionalized.Similarly,there was only a signal at 60 ppm,and its intensity did not change.As expected,the signal of unsubstituted position 3 at 80 ppm for C-3-OS starch became lower than that of CS,which means that position C3 of the AGU was acetylated.5.CS,OSCS,and OSC_s microgels were prepared via water-in-oil（W/O）inverse microemulsions for loading and releasing of epigallocatechin gallate（EGCG）.Strong hydrogen bonds between starch molecules in the W/O system and interplay between hydroxyl group of EGCG and oxygen atoms of starch microgels were formed.OSC_smicrogels had low average particle diameters and weak thermal stability with an irregular shape and a typical V-type crystal structure.When absorbed into OSCS and OSC_s microgels,encapsulation efficiency（EE）and clearance rate of 2,2-diphenyl-1-picrylhydrazyl（DPPH）for EGCG were in the range of 41.78-63.89%and 75.53-85.37%,respectively,which were higher than those of CS microgels.Moreover,OSC_s microgels controlled the slow release of EGCG into the gastrointestinal simulated system and therefore could be proposed as an encapsulating agent for loading polyphenols.6.CS/OS starch composite films with different soybean oil contents were prepared.Low concentrations of SO could facilitate the molecular interaction and the formation of hydrogen bonds between starch molecules.All films exhibited similar diffractograms and lower relative crystallinity values.Scanning electron microscopy（SEM）and atomic force microscopy（AFM）showed that the irregular and coarse surface structures（Ra:12.2 nm to41.7 nm）of the films were obtained with increasing SO concentration.A higher contact angle of 76.14°and lower water vapor permeability of 2.46×10^-12g·cm/cm²·s·Pa were obtained for CS/OS-1.5%SO film.The highest tensile strength value of 6.54 MPa was achieved for CS/OS-1.0%SO composite film,while the optimum elongation at break of 71.84%was displayed by the C/OS-1.5%SO composite film.更多还原