非晶颗粒态玉米淀粉的化学反应活性研究

将非晶颗粒态淀粉和原淀粉在阴、阳离子醚化剂条件下进行淀粉改性反应,取代度随醚化剂量的改变而改变,但由于整个颗粒处于非晶状态,导致非晶淀粉取代度和原淀粉相比有不同程度的提高:对羧甲基化,取代度平均提高13.03%,最高提高18.51%;对阳离子化来说,取代度平均提高13.29%,最高提高16.39%。在不同反应时间进行反应,也可以观察到相同的变化规律,因此将淀粉进行非晶化可显著提高淀粉的反应取代度,最终提高反应效率。     

超高压辅助制备醋酸酯淀粉结构性质研究

以玉米淀粉为原料,乙酸酐为反应试剂,NaCl为反应介质,采用超高压辅助制备醋酸酯淀粉,利用光学显微、X-射线衍射、快速黏度分析技术对醋酸酯淀粉结构性质进行分析。研究表明,颗粒态醋酸酯淀粉结晶类型与原淀粉相同,当处理压力为600 MPa时淀粉糊化,颗粒结构被破坏,A型结晶向V型结晶转换,但糊化并不利于醋酸酯淀粉取代度的增加。适量NaCl的添加有利于超高压处理时淀粉颗粒态的维持,因而有效提高了醋酸酯淀粉的取代度。当NaCl溶液浓度为1.0%、乙酸酐添加量为2.0%、压力为400MPa时,所制备的醋酸酯淀粉取代度达到最大值(0.090),且表现出较高的峰值黏度(400.00cP)。     

机械活化木薯淀粉制备低取代度醋酸酯淀粉的研究

以机械活化0.5h的木薯淀粉和木薯原淀粉为原料,以醋酸酐为酯化试剂,氢氧化钠为催化剂,制备低取代度木薯淀粉醋酸酯。以淀粉醋酸酯的取代度和反应效率为评价指标,分别研究反应温度、反应时间、醋酸酐用量、pH各因素对其取代度和反应效率的影响。实验结果表明,反应温度、反应时间、醋酸酐用量、pH对木薯淀粉醋酸酯的取代度和反应效率均有影响。机械活化能显著提高木薯淀粉醋酸酯化反应的取代度和反应效率。通过试验得到制备低取代度木薯淀粉醋酸酯的较佳工艺条件为:反应温度为30℃,反应时间为40min,醋酸酐用量为0.15mL,pH为8.5时,在此条件下制备的醋酸酯淀粉的取代度为0.075、反应效率为87.45%。并用红外光谱对醋酸酯淀粉进行分析。     

取代度对醋酸酯淀粉结构与性能的影响

取代度的大小对醋酸酯淀粉的性能有重要的影响。利用相同的制备工艺获取3种不同取代度的醋酸酯淀粉,采用红外光谱仪对淀粉的分子构成做出表征分析,在扫描电镜(SEM)下观察不同取代度醋酸酯淀粉颗粒的表面及内部的微观结构与原淀粉进行对比分析,并对浆液的凝沉性及淀粉的成膜性进行测试。结果表明,取代度较低的醋酸酯淀粉颗粒表面发生的变化较小,浆液的凝沉性及成膜性与原淀粉相差不大,浆膜较脆硬;高取代度的醋酸酯淀粉中酯基含量较明显,淀粉颗粒的网状结构突出,浆膜的吸湿率较低,保湿性较差。     

季铵醚化改性对磷酸酯淀粉浆料性能的影响

为提高磷酸酯淀粉浆料的使用性能,通过改变3-氯-2羟丙基三甲基氯化铵醚化剂对磷酸酯淀粉的投料比,制备了一系列具有不同季铵醚阳离子取代度的磷酸酯变性淀粉。通过性能对比实验,研究了这种变性淀粉的季铵阳离子化变性对浆液ζ电位、黏度以及黏附性能和浆膜性能的影响。结果表明：随着季铵阳离子取代度的增加,这种变性淀粉浆液的ζ电位升高,黏度明显提高;季铵阳离子化变性能够进一步改善磷酸酯淀粉对棉纤维的黏附性能;随着阳离子取代度的增加,对棉纤维的黏附性能增大,浆膜的断裂伸长率增大。     

木薯淀粉及木薯变性淀粉性质比较研究

测定了木薯淀粉、木薯羟丙基淀粉、羟丙基交联淀粉、醋酸酯淀粉、醋酸酯交联淀粉的冻融稳定性、透光率、凝沉、耐盐性、耐酸性、糊化特性等性质.实验结果表明:经过变性的木薯淀粉和原木薯淀粉有很大的不同,经过羟丙基化、羟丙基交联、醋酸酯化、醋酸酯交联后,分别引入了羟丙基、交联键、乙酰基等,使其具有较强的冻融稳定性,具有较高的透明度、耐盐性、耐酸性.据RVA分析,各种变性淀粉糊液性质较原淀粉有较大的提高.经过交联后糊液稳定性较原淀粉、羟丙基及醋酸酯淀粉有较大程度的提高,因此具有更为广阔的应用性.     

不同压力预处理对小麦醋酸酯淀粉制备的影响及产物结构表征

为探究不同预处理压力对淀粉酯化反应的影响效果,将小麦淀粉乳(40%)分别在0、20、40、60和80 MPa下处理后以醋酸酐进行酯化反应。通过傅里叶变换红外光谱仪(FTIR),偏光显微镜(PLM),X射线衍射(XRD)和扫描电镜(SEM)对小麦醋酸酯淀粉进行形貌和结构分析。结果表明:经过醋酸酐作用后,淀粉分子中引入酯羰基。高压均质预处理使小麦淀粉酯化程度显著提高,与未均质处理相比,取代度增幅达47.70%。醋酸酯淀粉在40 MPa下取得最大取代度0.096。偏光十字图显示随着压力增大,淀粉颗粒脐点处发生爆裂且裂缝沿脐点向外扩大。当均质压力达到80 MPa时,部分淀粉颗粒的双折射现象几乎消失。高压均质和低酯化反应都未改变小麦淀粉的A晶型,但压力迫使淀粉颗粒结晶结构破坏。醋酸酯淀粉保持了原小麦淀粉颗粒形貌,但在20 MPa下的淀粉颗粒出现剪切微变形和机械折叠。在80 MPa下,淀粉颗粒表面出现严重的机械损伤和断裂,一些大颗粒淀粉瓦解且相互之间有粘连,是取代度降低的原因之一。     

混合酸交联高温溶胀制备非晶颗粒态淀粉

采用已二酸和醋酸酯的混合酸交联处理玉米淀粉,然后对交联淀粉水浴加热至80℃制备非晶颗粒态淀粉.本文考察了不同的交联剂用量对玉米原淀粉非晶化的影响.用偏光显微镜观测处理后淀粉颗粒结构,结合X射线衍射曲线确认淀粉由多晶态向非晶态的变化.结果表明,当交联剂用量达到13%（淀粉干基）的时候,玉米淀粉可由多晶颗粒态的原淀粉制备出只含无定形结构的非晶颗粒态淀粉.     

磷酸酯型两性淀粉结构性能及其对纸张的增强作用

以木薯原淀粉、3-氯-2-羟丙基三甲基氯化铵和混合磷酸盐为主要原料,用半干法工艺合成了磷酸酯型两性淀粉,用FT-IR、XRD、SEM等对产物结构性能进行了表征;研究了其作为纸张增强剂对废纸浆的增强作用.结果表明,改性剂与木薯原淀粉反应不仅发生在无定形区,而且发生在结晶区;不仅发生在颗粒的表面,也可进入其内部;在一定条件下,产物的阳离子取代度随着磷酸盐用量的增加而减小,阴离子取代度随淀粉阳离子取代度的提高而降低.实验合成的磷酸酯型两性淀粉对纸张的增强作用显著,当添加量为1.O%(对绝干浆)时,纸张的抗张指数、耐破指数和撕裂指数分别比空白样提高了23.5%、20.3%、29.4%.     

3种马铃薯改性淀粉的理化性质及结构分析

以马铃薯淀粉为材料,制备氧化淀粉、醋酸酯淀粉、氧化醋酸酯淀粉,比较其理化性质,并通过红外光谱(FT-IR)、电子扫描显微镜(SEM)等对其结构进行分析。结果表明:氧化淀粉、醋酸酯淀粉、氧化醋酸酯淀粉比原淀粉透明度高、流动性好、附着力强、涂抹性好。FT-IR实验表明氧化淀粉有羧基的特征吸收峰,而氧化醋酸酯淀粉酯化改性过程中有醋酸酯基团的生成。SEM扫描实验显示氧化淀粉的外形比较规整多为球状或椭球状,表面较光滑;醋酸酯淀粉颗粒形状未发生大的改变,但规整度很差;氧化醋酸酯淀粉颗粒完整,表面粗糙,低取代度的酯化反应仅发生在淀粉颗粒表面。     

乙酰化对红薯淀粉性质的影响

以红薯淀粉为原料,醋酸酐为乙酰化剂,制备低取代的乙酰化红薯淀粉.通过制备不同取代度乙酰化淀粉(DS 0.044～0.096),与红薯原淀粉进行比较,对乙酰化淀粉的透明度、凝沉性、溶解度、溶胀度、黏度和质构特性等进行深入研究.结果表明,与原淀粉相比,红薯淀粉经乙酰化作用后,凝沉性明显减弱,乙酰化红薯淀粉透明度、溶解度和溶胀度都随着取代度的增加而增加,且明显高于原淀粉.乙酰化红薯淀粉的糊化温度降低6～10℃,最终黏度和回生值显著降低,硬度显著降低.     

Viscosity and Gelatinization Characteristics of Hydroxyethyl Starch

Viscosity and gelatinization characteristics of corn and potato starches as well as their hydroxyethyl derivatives were investigated. The inherent viscosity increased from 164 in native corn starch to 209 in etherified one of DS 0.18. The etherified corn starch gelatinized at lower temperature than native corn starch due to their increase of DS. Maximum viscosity decreased from 93°C to 69°C for the modified corn starch. The retrogradation of starch was minimized by etherification as retrogradation ability of corn starch from its solution decrease from 22% to 6%. This is of great importance when starch is used as blood plasma volume expander. Variable results were obtained with etherified potato starch which might be due to its high contents of phosphorus.     

The Reactivity of Native and Autoclaved Starches from Different Origins Towards Acetylation and Cationization

Native potato, waxy corn, corn, wheat, filed pea and lentil starches were autoclaved at 15 psi, 121°C for 1min. Scanning electron micrographs of the native and autoclaved starches showed no changes in granular surfaces and shapes. In all starches, the X-ray intensities at most of the d-spacings between 3-18 Å increased upon autoclaving, being more pronounced in potato. The X-ray patterns of cereals and legumes remained unchanged, while that of tuber (potato) became more cereal-like. Differential scanning calorimetry of the starch samples revealed that autoclaving increased the gelatinization transition temperatures of wheat but decreased that of potato; the changes observed in waxy corn, corn, field pea and lentil starches were very small. The gelatinization enthalpy of all native starches decreased upon autoclaving while the percentage decrease was highly marked in potato. Image analysis of the native and autoclaved starches revealed changes in the granule size distribution patterns. Also, the population mean area of all native starch granules considerably increased upon autoclaving. Acetyl binding capacity, measured at 5% and 10% acetic anhydride addition levels, was higher in autoclaved than in native starches. Furthermore, autoclaving had no influence on starch cationization, studied at 3% and 6% reagent addition levels. The results indicated that the changes in starch molecular organization caused by autoclaving enhanced its reactivity towards acetylation but not cationization.     

THE FLOW PROPERTIES OF NATIVE, HEAT-MOISTURE TREATED, AND ANNEALED STARCHES FROM WHEAT, OAT, POTATO AND LENTIL

The effect of heat-moisture treatment (30% moisture, 100C, 16 h) and annealing (75 % moisture, 50C, 72 h) on the flow behavior of gelatinized starch pastes from wheat, oat, lentil and potato starches were studied at a concentration of 6% starch with a cone and plate viscometer (Wells Brookfield RVTDV II CP 200). The power law rheological model (σ=Kγⁿ) was used to describe the flow behavior of the above starch pastes. All native starches exhibited a non-Newtonian shear thinning behavior. A thixotropic loop was evident only in oat starches and native potato starch. Among native starches, the magnitude of the shear thinning index (n) followed the order: oat > wheat > lentil > potato, while the corresponding order for the consistency index (K) was: potato > lentil > wheat > oat. Heat-moisture treatment decreased the K value of all starches. On annealing, K decreased in wheat and lentil starches, but increased in potato and oat starches. Heat-moisture treatment and annealing increased the n value of wheat, lentil and potato starches, but decreased that of oat starch. In all starches, the modification to the flow behavior was more marked on heat-moisture treatment than on annealing.     

Development of oxidised and heat-moisture treated potato starch film

This study investigated the effects of sodium hypochlorite oxidation and a heat-moisture treatment of potato starch on the physicochemical, pasting and textural properties of potato starches in addition to the water vapour permeability (WVP) and mechanical properties of potato starch films produced from these starches. The carbonyl contents, carboxyl contents, swelling power, solubility, pasting properties and gel texture of the native, oxidised and heat-moisture treated (HMT) starches were evaluated. The films made of native, oxidised and HMT starches were characterised by thickness, water solubility, colour, opacity, mechanical properties and WVP. The oxidised and HMT starches had lower viscosity and swelling power compared to the native starch. The films produced from oxidised potato starch had decreased solubility, elongation and WVP values in addition to increased tensile strength compared to the native starch films. The HMT starch increased the tensile strength and WVP of the starch films compared to the native starch.     

Functional Properties and Retrogradation of Heat‐Moisture Treated Wheat and Potato Starches in the Presence of Hydroxypropyl β‐cyclodextrin

Some functional and retrogradation properties of native and heat‐moisture treated potato and wheat starches were examined in the presence of hydroxypropyl β‐cyclodextrin (HPβ‐CD). HPβ‐CD increased swelling factor, amylose leaching, and solubility of both native and heat‐moisture treated wheat starches but it had less impact on corresponding potato starches. Gelatinization enthalpy of native wheat starch was decreased in the presence of HPβ‐CD but was increased in potato starch with increasing concentration. Reduction of amylose‐lipid complex endotherm in both native and heat‐moisture treated wheat starch was observed in the presence of HPβ‐CD. Heat‐moisture treatment did not change the transition parameters of amylose‐lipid complex showing its resistance to hydrothermal treatment. HPβ‐CD greatly decreased the pasting temperature of wheat starch. Cold paste viscosity of both native and heat‐moisture treated wheat starch was increased by HPβ‐CD to a greater extent than corresponding potato starch. Amylopectin retrogradation of all the starches was unaffected in the presence of HPβ‐CD but heat‐moisture treatment slightly decreased retrogradation of potato starch. These results suggest that HPβ‐CD can disrupt the amylose‐lipid complex within the starch granule in both native and heat‐moisture treated wheat starch but has no influence on amylopectin retrogradation. However, greatly increased wheat starch setback with HPβ‐CD indicates its greater effect on wheat starch amylose retrogradation.     

Effect of debranching and storage condition on crystallinity and functional properties of cassava and potato starches

Debranching starch by pullulanase is considered to improve the RS content of starch which is widely used to produce the starch‐based foods with high‐health benefit impacts. In this study, the cassava and potato starches were debranched by pullulanase, followed by an autoclave treatment and storage at −18°C, 4°C, or 25°C to investigate their crystallinity and functional properties. After debranching, the potato starch contained significantly higher CL (35.4 glucose units) than did the cassava starch (32.4 glucose units). The debranched cassava and potato starches after retrogradation at the storage temperatures had a typical B‐type crystalline structure although the native cassava and potato starches exhibited the different crystalline forms (A‐ and B‐type, respectively). The RS contents of the debranched cassava and potato starches significantly improved with higher RS content of the debranched potato starch than that of the debranched cassava starch at the same storage condition. The storage temperature significantly affected the RS formation of the debranched starches with the highest RS content at storage temperature of −18°C (35 and 48% for the debranched cassava and potato starches, respectively). The debranched starches had significantly lower viscosities and paste clarities but higher solubilities than did the native starches. As a result, the debranched cassava and potato starches can be considered for use not only in functional foods with enhanced health benefits but also in pharmaceutical and cosmetic industries.     

柠檬酸甘薯淀粉酯制备工艺优化及性质研究

以甘薯淀粉为原料,优化制备高取代度柠檬酸淀粉酯的条件并对其性质进行研究。以柠檬酸淀粉酯取代度为指标,对影响取代度的因素进行研究,通过响应面优化制备工艺。得到最优工艺条件为pH1.5、反应温度148.21℃、反应时间6.45h、柠檬酸与淀粉干基质量比为0.59,在此条件下可制得取代度高达0.30的柠檬酸甘薯淀粉酯;柠檬酸甘薯淀粉酯具有很好的抗酶解性,抗性淀粉含量随取代度的增加而增加,当取代度达0.13时,抗性淀粉含量达92%;对比原淀粉,柠檬酸甘薯淀粉酯平均聚合度降低,白度先增高后降低。     

Effect of Acetylation on Some Properties of Corn and Potato Starches

Corn starch and starches separated from different potato cultivars were acetylated to evaluate the effect of plant source on the physicochemical, morphological, thermal, rheological, textural and retrogradation properties of the starches. Corn starch showed a lower degree of acetylation than potato starches under similar experimental conditions. The degree of acetylation for different potato starches also differed significantly. Morphological examination revealed that the granules of acetylated Kufri Chandermukhi and Kufri Sindhuri starches tended to appear as fused and less smooth than native starch granules. Acetylation of corn and potato starches decreased the transition temperatures and enthalpy of gelatinization and increased swelling power and light transmittance. However, the change in these was greater in the potato starches with higher percentage of small sized granules. Acetylated starches showed higher peak G', G'' and lower tan δ than their counterpart native starches during heating. Among the starches from different cultivars, the change in the rheological parameters after acetylation differed to a significant extent. The retrogradation was observed to be negligible in the acetylated cooked starch pastes. Results implied that the change in functional properties of starches with acetylation depends on source and granule morphology of native starch.