【作者】 马森；

【导师】 于淑娟；

【作者基本信息】 华南理工大学 ， 制糖工程， 2012， 博士

【摘要】 甜菜粕是甜菜制糖过程中的副产物，含有果胶、纤维素等功能性膳食纤维，这些膳食纤维被认为是维系人体健康、不能被其它物质所代替、具有特殊生理功能的营养素。目前甜菜粕资源尚未得到合理利用，本论文研究了甜菜粕膳食纤维的提取、脉冲电场改性、花生酸酐改性、离子液体为介质的物理和化学改性、结构鉴定及相关的作用机理。以期合理利用甜菜粕资源，促进我国制糖工业和相关产业健康可持续发展。分别采用有机酸法、超声波法和压力法提取甜菜粕果胶。研究发现采用柠檬酸、马来酸和乳酸作为提取剂的有机酸法得到的果胶品质不同，果胶得率和半乳糖醛酸(GalA)含量不仅受酸的强热性质影响，还受它们本身三元、二元、一元酸的特性影响，确定最佳条件为采用柠檬酸调pH至1.5，85oC提取2h，果胶得率和GalA含量分别为17.1%和78%。超声波法在单因素实验基础上采用Box-Behnken设计和响应面分析，确定最佳提取条件为超声功率900W，超声时间45min，pH1.5，果胶得率和GalA含量分别为6.3%和71%，经拟合得到果胶得率和GalA含量的两个二阶方程能很好的预测果胶的品质。压力法得到的最佳提取条件为在20Mpa，160oC下提取90min，果胶得率和GalA含量分别为22.5%和65%。探讨了三种方法制备的甜菜粕果胶在结构组成上的差异，并对甜菜果胶的流变学特性进行了深入研究。发现不同方法制备的果胶在得率、总糖含量、半乳糖醛酸含量和分子量方面均存在显著差异。其中，有机酸法得到较理想的得率，总糖含量和半乳糖醛酸含量最高，而分子量相对较低。超声波法和压力法制备果胶的酯化度没有显著差异，两者均比有机酸法制备果胶的酯化度高。流变学特性研究表明甜菜果胶的粘度随着果胶浓度的增加而增大，随着剪切速率的增加而减小。温度的升高、pH值和静置时间的增加都会降低果胶的粘度，而适当提高金属离子浓度和糖浓度可使果胶粘度显著增大。研究了脉冲电场对甜菜粕果胶的改性，试验条件主要包括电场强度18-30kV/cm和脉冲时间806-2418μs。用X-射线衍射、蒸发光散射和红外光谱等仪器技术评价改性果胶的物化特性，并用布金汉(Buckingham)定理推导脉冲电场降解甜菜果胶的过程仿真模型。结果表明，脉冲电场处理破坏了果胶的晶型，果胶的酯化度、分子量和平均粒径随着电场强度和脉冲时间的增加而减少。脉冲电场对果胶降解的过程仿真模型能很好的描述和评价降解过程。脉冲电场技术是降低果胶酯化度和分子量的极好方法，在食品工业有很好的应用前景。研究了无溶剂条件下甜菜果胶与花生酸酐之间的反应，探讨了反应温度(130-170oC)、反应时间(20-60min)、酸酐用量(0.5:1-2:1)、催化剂用量(0.05-0.15%)和电场强度(18-30kV/cm)对果胶衍生物产率的影响。结果表明，无溶剂介质条件下，花生酸酐可以直接和甜菜果胶发生酯化反应，将花生酸基团引入果胶中。脉冲电场预处理有利于果胶-花生酸酯的合成，果胶的花生酸化反应随着反应时间、花生酸酐用量、催化剂用量的增加而提高，增加反应温度能促进果胶的花生酸化反应，但当高于160oC，产物的得率降低。红外光谱、X-射线衍射和核磁共振光谱分析结果证实了花生酸酐和果胶的羟基部位发生了酯化反应。反应后，果胶衍生物的热稳定性升高。研究了在离子液体1-丁基-3-甲基咪唑氯酸盐中，超声波辅助甜菜粕纤维素的均相戊二酸化反应，探讨了超声时间，反应温度，戊二酸酐和纤维素中单位葡萄糖摩尔比和反应时间对纤维素取代度的影响，并通过红外光谱、固体核磁共振光谱和热稳定性分析对甜菜粕纤维素衍生物的性质进行表征。研究发现，不使用任何催化剂，甜菜粕纤维素和戊二酸酐可发生均相戊二酸化反应，得到不同取代度(0.74-1.44)的纤维素衍生物，其取代度随着超声时间(10-40min)，反应时间(20-120min)，反应温度(90-110oC)和酸酐用量(2:1-6:1)的增加而增加。与初始纤维素相比，改性过的纤维素的热稳定性降低。探讨了过氧化物酶对果胶和蛋白质形成的双层乳状液的稳定性影响。研究发现，过氧化物酶和过氧化氢的加入，实现了果胶分子之间的交联，其最佳条件为酶用量200U/g，过氧化氢浓度0.02%，反应温度40oC和反应时间120min。随着改性果胶浓度的增加，乳状液液滴的电荷绝对值增大，界面张力增大，乳状液稳定性增强。双层乳状液在中性pH稳定性最佳，在酸性pH稳定性较差。更多还原

【Abstract】 Sugar beet pulp (SBP), a byproduct of sugar beet engineering, contains dietary fiber suchas pectin and cellulose, which is cosidered as irreplaceable beneficial nutrients with specicalphysiological functions. However, it is still underutilized today. In order to fully utilize SBPsource and promote healthy and sustainable development of China’s sugar engineering, themethods of extracting pectin from beet pulp, modification of pectin with pulsed electric fieldand arachidic anhydrate, homogeneous derivatization of cellulose in ionic liquids and itsrelated structure and mechanism analysis were studied in this thesis.The methods of organic acid, ultrasound and pressure were used to extract pectin fromSBP. The results indicated that the pectins obtained by citric acid, maleic acid and lactic acidwere different in yield and galacturonic acid (GalA) content, respectively. The discrepanciesof pectin yields and GalA content extracted with the methods were not only affected by theirorganic feature but also by their relatively strong or weak nature. The optimal yield (17.1%)and GalA content (78%) were obtained at pH1.5，85oC for2h with critic acid as extractant.Box-Behnken design and response surface analysis were applied in ultrasonic method basedon single factor experiment. Results indicated that the highest yield of6.3%and GalA contentof71%were obtained at pH1.5for45min with ultrasonic power of900W. Twosecond-order equations were caculated, which could be used for predicting the quality ofpectin. In additon, the optimal conditons of pressure method had also been studied. Themaximal yield and GalA content were22.5%and65%, respectively, with the optimalextraction conditions of20Mpa presusre for90min at160oC.The composition and rheological properties of SBP pectin extracted by three mehtodswere studied in this section. The results indicated that there were significantly difference inyield, carbohydrate content, GalA content and molecular weights of pectin. The pectinextracted from organic acid method has a better yield, and its carbohydrate content andgalacturonic acid were the highest, but its molecular weights were relatively low. There wereno significant difference in degree of esterification (DE) between ultrasonic method andpressure method, both of them had higher DE than organic method. The rheologicalproperties of pectin showed that the viscosity of pectin increased with increasing concentration, and decreased with increasing shear rate. The increase of temperature, pHvalue and standing time reduced the viscosity of the pectin, but an appropriate increase in ionconcentration and carbohydrate concentration would enable the viscosity significantlyincreased.The modification of pectin induced by pulsed electric field (PEF) was studied in thissection. Experimental parameters including electric field intensity (18-30kV/cm) and pulsetime (806-2418μs) were used, and the physicochemical properties of PEF-treated pecitn wereevaluated by various instrumental techniques such as, X-ray diffraction patterns, Dynamiclight scattering spectra and FT-IR spectra. The process of pectin degradation was deduced byBuckingham theorem. The results showed that crystalline regions of pectin were destroyedafter being treated with PEF, and the DE, molecular weight and particle size of pectindecreased with the increase of electric field intensity and pulse time. The process of pectindegradation could be evaluated by two obtained simulation models. Results revealed that PEFtechnology is an effective method to obtain the pectins with different molecular-weights andDEs, and get a desired production in food application.The solvent-free modification of SBP pectin with arachidic anhydride were studied inthis section. The parameters included reaction temperature (130-170oC), reaction time (20-60min)、anhydride usage (0.5:1-2:1)、catalysis usage (0.05-0.15%) and electric intensity (18-30kV/cm). The results showed that pectin-arachates were prepared in one-step solvent-freemodification. The PEF pretreatment had a favourable effect on this reaction, and the weightpercent gain (WI) of pectin derivatives increased with increasing temperature, reaction time,anhydride usage and catalysis usage. However, the WI decreased when temperaute was over160oC. Evidence of pectin modification was provided by FT-IR spectra, X-ray diffractionpatterns and1H Nuclear magnetic resonance (NMR) spectra. Thermal gravimetric analysis(TGA) of modified pectin indicated a higher thermal stability than untreated pectin.Cellulose glutarates were synthesized from beet pulp cellulose and glutaric anhydride inionic liquid (IL)1-butyl-3-methylimidazolium chloride assisted by ultrasound. Parametersinvestigated included ultrasound time, temperature, the molar ratio of glutaricanhydride/anhydroglucose units in cellulose (MRO), and reaction time. The cellulose derivatives were characterized by FT-IR spectra, solid-state CP/MAS13C NMR spectra andTGA. The results showed that the synergy of the combined use of ultrasound and IL hadsuccessfully enhanced the degree of substitution of cellulose glutarates under theexperimental conditions of the present study, and its DS increased with the increment ofultrasond time (from10to40min), temperature (from90to110oC), the MRO in a range from2:1to6:1and reaction time (from20to120min). Besides, the modified cellulose showedlower thermal stability than native cellulose.The stability of a double emulsion made from SBP pectin and Bovine Serum Albuminwas evaluated in the present research. The results showed that the cross-linked stucture wasformed between pectin molecules after peroxidase and hydrogen peroxide added. The optimalconditions of pectin modification were enzyme dosage of200U/g, concentration of hydrogenperoxide0.02%, reaction temperature of40oC and the reaction time of120min. With theconcentration of modified pectin increased, the charge absolute value, interfacial tension andof double emulsion increased, indicating the stability of double emulsion increased. Thedouble emulsion made from modified pectin and protein had a better stability in neutral pHwhile relative unstable in acid pH conditions.更多还原