物理修饰对淀粉抗消化性能和分子结构的影响

淀粉颗粒通过物理修饰,调节不同的水质量分数、温度、压力和处理时间,可以改变淀粉的抗消化性能。实验结果表明,压力和水质量分数对淀粉抗消化性能的影响显著(P<0.05),温度和时间这两个因素对淀粉的抗消化性能影响较小(P<0.05)。由正交实验结果可知,获得高抗消化淀粉质量分数的最佳处理条件为:温度120℃,压力9×105Pa,水质量分数为20%,处理时间1.5 h。经核磁共振、X射线衍射和差示扫描量热法对物理修饰后的淀粉分子结晶结构和热性能的分析发现,随着淀粉抗消化性能的提高,分子的有序化程度提高,但这些有序化的结构发生了由B型向V型的晶型转变。     

羧甲基取代度对淀粉生物降解性能的影响

利用半生物体内模型和扫描电子显微技术系统地研究了取代度在0 05至0 40的羧甲基淀粉的生物降解性能,并用微生物降解代谢过程中CO2的净生成速度和剩余淀粉质量分数对羧甲基淀粉的生物降解速度和降解程度进行了表征。结果表明,淀粉经羧甲基化后,有利于微生物分泌的淀粉酶对淀粉分子链的水解。但随着羧甲基取代度的提高,水解产物中的羧甲基基团的质量分数增大,淀粉的生物降解速度和程度先增大后减少,说明羧甲基低聚糖不利于被微生物完全代谢。当取代度≤0 10时,羧甲基化促进玉米淀粉的生物降解速度和程度;当取代度为0 40时,羧甲基化抑制淀粉的生物降解,30d后其生物降解速度和程度分别为9 82mg·g-1·d-1和67 1%。淀粉的生物降解性能可以通过调节羧甲基取代度的大小来控制。     

浆液体系中木薯淀粉乙酰化反应均匀性及基团分布特征

以木薯淀粉为原料、乙酸酐为酰化剂,在浆液体系中制备乙酰化淀粉,采用4.3 mol·L~(-1)CaCl2溶液对乙酰化淀粉颗粒进行化学表面糊化处理,获得不同表面糊化程度的剩余淀粉颗粒,通过SEM、XRD表征剩余颗粒的形貌及结晶结构,采用皂化法测定剩余颗粒的乙酰基含量,并利用最小二乘法拟合取代基含量在淀粉颗粒径向上的分布曲线,考察乙酰化反应均匀性和乙酰基分布的影响因素。结果发现:乙酰基团在淀粉颗粒中呈现外高内低的非均匀分布,30%以上的乙酰基分布在对比半径0.9～1.0的外部区域,而在0～0.7比较大的范围内仅占28%左右;反应温度升高、反应时间延长和酰化剂用量增大,乙酰基含量在淀粉颗粒内的分布离散程度减小,有利于乙酰化反应和乙酰基团分布更趋均匀;随着表面糊化程度增大,剩余颗粒均能保持木薯淀粉的形貌和"A"型结晶结构特征,但粒径稍有减小,结晶度整体呈现下降趋势,部分稍有突跃。以上结果说明,结晶结构与非晶结构在木薯淀粉颗粒内交替存在,且各区域结晶区和非晶区比例存在一定差异,适当改变反应条件可改善木薯淀粉颗粒内乙酰化反应和乙酰化基团非均匀分布的状况。     

抗消化淀粉薄膜的结晶结构及消化道靶向性研究

研究了抗消化淀粉薄膜的表面形貌和结晶结构.抗消化淀粉薄膜的表面粗糙,在pH为1.2和6.8的模拟缓冲液中分别浸泡2 h和6 h仍然保持完整;抗消化淀粉在成膜过程中发生结晶取向,其结晶形态为B型.体外模拟实验表明,抗消化淀粉薄膜在人工胃液和人工小肠液中都有良好的抗消化性能,且随着抗消化淀粉含量的增加,抗消化性能越显著.     

浆液体系中木薯淀粉乙酰化反应均匀性及基团分布特征

以木薯淀粉为原料、乙酸酐为酰化剂，在浆液体系中制备乙酰化淀粉，采用4.3 mol·L^-1 CaCl₂溶液对乙酰化淀粉颗粒进行化学表面糊化处理，获得不同表面糊化程度的剩余淀粉颗粒，通过SEM、XRD表征剩余颗粒的形貌及结晶结构，采用皂化法测定剩余颗粒的乙酰基含量，并利用最小二乘法拟合取代基含量在淀粉颗粒径向上的分布曲线，考察乙酰化反应均匀性和乙酰基分布的影响因素。结果发现：乙酰基团在淀粉颗粒中呈现外高内低的非均匀分布，30%以上的乙酰基分布在对比半径0.9~1.0的外部区域，而在0~0.7比较大的范围内仅占28%左右；反应温度升高、反应时间延长和酰化剂用量增大，乙酰基含量在淀粉颗粒内的分布离散程度减小，有利于乙酰化反应和乙酰基团分布更趋均匀；随着表面糊化程度增大，剩余颗粒均能保持木薯淀粉的形貌和“A”型结晶结构特征，但粒径稍有减小，结晶度整体呈现下降趋势，部分稍有突跃。以上结果说明，结晶结构与非晶结构在木薯淀粉颗粒内交替存在，且各区域结晶区和非晶区比例存在一定差异，适当改变反应条件可改善木薯淀粉颗粒内乙酰化反应和乙酰化基团非均匀分布的状况。     

聚乳酸改性糯玉米淀粉的制备及表征

以糯玉米淀粉为原料、异辛酸亚锡为催化剂,在丙交酯熔融体系中制备了聚乳酸改性糯玉米淀粉。建立了聚乳酸改性糯玉米淀粉取代度的1HNMR测试方法,以取代度为响应值,反应时间、反应温度、丙交酯添加量为考察因素,通过单因素和响应面实验优化了聚乳酸改性糯玉米淀粉的合成工艺,得到最优工艺为：反应时间12.46 h,反应温度111.75℃,丙交酯添加量为淀粉质量的258%,预测最大取代度为0.0253,通过实际操作条件调整后实际取代度为0.0238。对最优条件下制备的聚乳酸改性淀粉进行了系列表征,证实聚乳酸改性糯玉米淀粉的颗粒结构没有被完全破坏,晶型、相对分子质量等性能优于溶剂法传统技术制备的聚乳酸改性糯玉米淀粉。     

不同pH环境对醋酸酯淀粉薄膜结晶结构及降解性能的影响

为了考察醋酸酯淀粉薄膜在不同环境中的降解特性,将醋酸酯淀粉薄膜分别置于pH =1.2、7、12的模拟环境中一定时间进行降解,利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、接触角测量仪、材料试验机、动态热机械分析仪(DMA)对不同浸泡时间的薄膜失重率、表面形貌、结晶结构、疏水性能及力学性能等进行了表征和分析.结果表明:不同pH环境对醋酸酯淀粉薄膜结晶结构及降解性能均有一定程度的影响.在降解过程中薄膜仍然保持V型结晶结构,疏水性能和断裂伸长率显著下降,拉伸强度呈先上升后下降的趋势.碱性环境中,薄膜在前14 d的降解速率最大,表面出现局部孔洞,结晶度呈逐渐升高的趋势;酸性环境中,降解后期降解程度较大,表面有明显缺陷,结晶度在降解前期上升,28 d后开始下降.研究结果为研制和开发不同降解时间要求和应用环境的淀粉基生物降解材料提供了基础数据.     

非晶颗粒态马铃薯淀粉微生物降解特性

用光学显微分析测试方法,以原马铃薯淀粉为参照,对非晶颗粒态马铃薯淀粉在微生物作用下的降解过程进行了观察和研究。结果发现,非晶淀粉颗粒松散的无定形结构以及形成的爆裂孔,大大提高了微生物降解反应活性。在微生物作用下,从淀粉颗粒的爆裂孔开始,沿着淀粉颗粒爆裂孔逐步深入,直至最后将淀粉颗粒完全降解,而原淀粉颗粒具有致密的结晶结构,淀粉颗粒表面没有明显的孔洞,因此在同样条件下的生物降解活性,要远远低于非晶颗粒态淀粉。     

环己烷辅助超临界CO_2流体制备淀粉酯

利用环己烷等助剂辅助超临界CO_2流体制备辛烯基琥珀酸淀粉酯,研究助剂辅助效果,优化超临界酯化反应条件,并采用NMR、SEM和XRD等进行结构表征。结果表明:环己烷有助于改善超临界CO_2对酯化剂的溶解性能,酯化反应效率约为无助剂时的3.0倍;反应温度、压力、时间及酯化剂用量等对反应也有重要影响,当温度90℃、压力12 MPa、酯化剂用量2%、时间3 h时,反应效率高达83%以上;酯化剂用量为4%时,取代度为0.0191,反应效率可达61%。结构表征发现淀粉分子中引入了酯化基团,产品依然保持淀粉颗粒特征和A型结晶结构,但颗粒表面遭到局部破坏,结晶度降低。以上结果说明,环己烷提高了超临界淀粉酯化反应效率,改善了酯化反应条件。     

淀粉辛酸酯的制备及其乳化性能的研究

将淀粉与辛酰氯在有机溶剂中反应制备了不同取代度的淀粉辛酸酯,采用红外光谱(FTIR)对其结构进行了表征。此外,进一步研究了淀粉辛酸酯在大豆油与水乳液体系中取代度、淀粉辛酸酯的质量分数和油水体积比等条件对淀粉辛酸酯乳液乳化性及乳化稳定性的影响。结果表明,在取代度为0.37、淀粉辛酸酯质量分数为7%时,淀粉辛酸酯显示出较好的乳化性能。在大豆油/水乳液体系中,当油水体积比为4∶6时,乳液的乳化性较好。而在油水体积比为2∶8时,乳液的乳化稳定性较好。     

Biodegradation of low‐density polyethylene‐banana starch films

Films were prepared by extrusion using acetylated and oxidized banana starches at different concentrations mixed with low‐density polyethylene, and their biodegradation (buried in soil) at different storage times was studied. Morphological, thermal, and mechanical characteristics of the films after degradation were tested. Films made of acetylated banana starch degraded most rapidly and those prepared with oxidized starch had the slowest degradation time. The type of chemically modified starch plays an important role in degradation of film. Burying the films produced a decrease in degradation temperature at the longest storage time, and there was a longer interval in the films prepared with native banana starch, followed by those made of acetylated starch. The buried in soil films had a broad phase transition and, consequently, an increase in enthalpy. This is due to degradation of amorphous starch zones with an increase in the crystallinity. Electron scanning microscopy analysis revealed greater degradation at longer storage time and a more marked effect in the films made of modified banana starch. Mechanical properties of the films were affected by degradation, and these varied depending on the modified banana starch used. The use of biodegradable polymers such as chemically modified banana starch might be feasible for making films with a high rate of degradation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

机械活化对玉米淀粉结晶结构与化学反应活性的影响

采用搅拌球磨机对玉米淀粉进行机械活化，用X射线衍射仪、差示扫描量热仪、扫描电子显微镜及粒度分析仪等考察了机械活化对玉米淀粉结晶结构、热特性、颗粒形貌及粒度变化的影响。并将不同活化时间的玉米淀粉在相同条件下与乙酸酐进行酯化反应及与丙烯酰胺进行接枝共聚反应，通过研究机械活化对酯化反应取代度、接枝共聚反应接枝率与接枝效率的影响规律来探讨机械活化对玉米淀粉化学反应活性的影响。结果表明，机械活化预处理能显著提高玉米淀粉酯化反应的取代度及接枝共聚反应的接枝率与接枝效率，说明机械活化能有效地提高玉米淀粉的化学反应活性。其原因是玉米淀粉在机械活化过程中其结晶结构与颗粒形貌均受到破坏，结晶度降低，最终由多晶态转变成非晶态。并随活化时间的延长，糊化温度及糊黏度下降，流动性增强，从而使反应试剂的扩散阻力下降，易于扩散到淀粉分子中参与反应。     

Preparation and in vitro controlled release behavior of a novel pH-sensitive drug carrier for colon delivery

The synthesis of a novel complex system designed for colon-targeting drug delivery was reported. The complex was prepared by dialdehyde konjac glucomannan and adipic dihydrazides to form steady Schiff base, and crosslinking with 5-aminosalicylic acid (5-ASA) through glutaraldehyde as a cross-linking agent. The structure was characterized by Fourier transform infrared (FTIR) spectroscopy, ¹³C NMR, wide angle X-ray diffraction (WAXRD) and thermogravimetric analysis. In vitro release of 5-ASA from the complex showed that the total released 5-ASA after 24 h in buffer solution at pH 1.2, 6.8, and 7.4 were 4, 59, and 21%, respectively. The release rate of 5-ASA can be controlled by tuning the pH value more effectively. The results indicated that the novel pH-sensitive complex could be potentially useful for colon-targeting drug delivery system.     

Photobiodegradation of low‐density polyethylene/banana starch films

The effects of the starch content, photosensitizer content, and compatibilizer on the photobiodegradability of low‐density polyethylene (LDPE) and banana starch polymer blend films were investigated. The compatibilizer and photosensitizer used in the films were PE‐graft‐maleic anhydride (PE‐g‐MA) and benzophenone, respectively. Dried banana starch at 0–20% (w/w) of LDPE, benzophenone at 0–1% (w/w) of LDPE, and PE‐g‐MA at 10% (w/w) of banana starch were added to LDPE. The photodegradation of the blend films was performed with outdoor exposure. The progress of the photodegradation was followed by determining the carbonyl index derived from Fourier transform IR measurements and the changes in tensile properties. Biodegradation of the blend films was investigated by a soil burial test. The biodegradation process was followed by measuring the changes in the physical appearance, weight loss, and tensile properties of the films. The results showed that both photo‐ and biodegradation rates increased with increasing amounts of banana starch, whereas the tensile properties of the films decreased. The blends with higher amounts of benzophenone showed higher rates of photodegradation, although their biodegradation rates were reduced with an increase in benzophenone content. The addition of PE‐g‐MA into polymer blends led to an increase in the tensile properties whereas the photobiodegradation was slightly decreased compared to the films without PE‐g‐MA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2725–2736, 2006     

Structural changes of starch/polyvinyl alcohol biocomposite films reinforced with microcrystalline cellulose due to biodegradation in simulated aerobic compost environment

Starch/Polyvinyl alcohol (PVA) based biocomposite films reinforced with micro crystalline cellulose (MCC) (10 wt %) particles were prepared by solution casting method, incorporating glycerol as plasticizer. These biocomposite films were subjected to biodegradation at ambient temperature in a simulated aerobic compost pit. The extent of biodegradation of these films was studied in terms of weight loss. The corresponding changes in the structure of the films were observed using scanning electron microscopy, X‐Ray diffraction study, and differential scanning calorimetry. The melting point of PVA component of the biocomposite film shifted from 204 to 223°C with increase in biodegradation time and a remarkable difference was observed in their melt crystallization behavior. The unreinforced films also showed a similar trend, but the increase in the crystallinity of PVA was more pronounced in MCC reinforced films than that observed in the unreinforced ones. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Synthesis and characterization of novel pH-, ionic strength and temperature- sensitive hydrogel for insulin delivery

A series of novel silane crosslinked hydrogel was prepared from kappa carrageenan (KC), acrylic acid (AA) using vinyltriethoxysilane (VTESi). Potassium persulphate initiated the grafting and copolymerization reactions between reactants. In addition, the condensation of the hydroxyl groups of KC and VTESi resulted into crosslinking. Novelty of this work is the use of VTESi as crosslinker for such a composition of hydrogel. The structure of prepared hydrogels was characterized by Fourier transform infrared spectroscopy. The analysis of spectra confirmed the presence of feed components in the prepared hydrogels. Thermogravimetric analysis showed an increase in the stability of the hydrogels either having high AA contents or crosslinker amount. The effect of feed components, pH (buffer, non-buffer), electrolytic media and temperature on the swelling behaviour of the hydrogels is reported here.Most promising results with high swelling ratio were observed in hydrogel having low monomeric ratio (KC:AA = 1:7). pH response of this hydrogel in acidic and neutral pH makes it suitable for drug delivery application. Insulin, a protein based drug was selected as a model drug. It requires its delivery in small intestine for proper action; therefore its release behaviour was studied in-vitro in simulated stomach and intestinal fluids. The release profile of insulin showed negligible release in simulated gastric fluid (SGF) and sustained release in simulated intestinal fluid (SIF). The obtained results are in good agreement with the swelling response of this hydrogel. The weak structure of this hydrogel makes it preferable for drug delivery, as it is able to get crumbled after releasing the drug for 6 h at neutral pH.     

Mesoporous tablet-shaped potato starch aerogels for loading and release of the poorly water-soluble drug celecoxib

In this study, after determination of the optimal values of the effective parameters in the synthesis using experimental design software, tablet-shaped potato starch aerogels were synthesized at the optimal condition in order to be used as a drug carrier. The celecoxib, as the model drug, was loaded into the aerogel matrix during the solvent exchange step. FTIR(Fourier Transform Infrared Spectroscopy), FESEM and HRTEM(Transmission Electron Microscopy) analyses showed that celecoxib has been successfully loaded into aerogel matrix. Also, XRD analysis showed that most of the celecoxib has been loaded in amorphous form. In vitro studies were performed in both simulated gastric and intestinal fluids. The release kinetics showed that the loaded celecoxib dissolved faster than crystalline celecoxib. At rotational speed of 100 r·min~(–1), about 26% and 50% and at rotational speed of 50 r·min~(–1),about 20% and 42% drug was released during the first 30 min of soaking in the simulated gastric fluid and simulated intestinal fluid, respectively. The release of the mentioned drug was increased up to 60% and 98% at a rotational speed of 100 r·min~(–1) and up to 46% and 93% at a rotational speed of 50 r·min~(–1) at the end of 5 h in the simulated gastric fluid and simulated intestinal fluid, respectively. It could be concluded that potato starch aerogels can be very useful in many drug delivery applications along with conventional micronization techniques. Modeling of release data showed that the release kinetics follows the Korsmeyer Peppas model, which considers phenomena of matrix erosion and drug diffusion.     

Effect of starch addition on compression‐molded poly(3‐hydroxybutyrate)/starch blends

Because of their biocompatibility and total biodegradability, poly(3‐hydroxybutyrate) (PHB) and starch have attracted attention as promising raw materials for manufacture of single‐use plastic items and biomaterials. PHB/maize starch blends with starch contents in the range of 0–50 wt % were processed in an internal mixer, and their compression‐molded films were characterized by tensile tests, X‐ray diffraction, thermogravimetric analysis, wettability measurements, and scanning electron microscopy. Water and glycerol were used as plasticizers. The results indicated that the thermal degradation behavior of the blends were similar to that of pure PHB films. All the blends showed heterogeneous morphology, wherein starch granules were dispersed in continuous PHB‐rich matrix. Despite the decrease in elongation at break and tensile strength, starch incorporation of up to 30 wt % into PHB matrix resulted in materials as hard as pure PHB films, but exhibiting less crystallinity and more hydrophilic character, which might lead to a higher biodegradation rate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4338–4347, 2006     

Structure‐Property Relationships of Extruded Starch, 2 Extrusion Products from Native Starch

The supermolecular structure and morphology of extruded flat films from several native starch materials of A‐ and B‐crystal type were investigated by wide‐angle X‐ray scattering and scanning electron microscopy. The degree of crystallinity and crystallite dimensions of both the different starting materials and the extruded films were determined and a scheme of the lattice transformations resulting from extrusion was established. The conditions of structure formation of the extruded starch films were varied in relation to plasticizer composition and extruder zone temperatures. The mechanical properties and biodegradability of the films were also measured. The extruded starches crystallized in the V_H polymorph with crystallinities between 33 and 41% and crystallite sizes of up to 35 nm. An increase in crystallite size was found for all starches (sometimes a doubling) with increasing extruder middle zone temperatures from 120 up to 210°C. For extruded potato and maize starches a steep rise in strength and modulus and a drop in elongation was observed above 190°C. Purified amylopectin from maize showed after extrusion the crystalline A‐type and small amounts of B polymorph with small crystallites (up to 3 nm) and the best mechanical performance with strengths and moduli of about 20 MPa and 1 500 MPa, respectively, for the present extrusion conditions. Native starch films that include 20 to 30% plasticizer biodegrade rapidly in 25 d consuming 90% of the oxygen needed for complete degradation, as analyzed by the Sapromat test.