Impact of Pre‐Processing of Montmorillonite on the Properties of Melt‐Extruded Thermoplastic Starch/ Montmorillonite Nanocomposites

A simple and environmentally‐friendly processing method was used to prepare thermoplastic starch (TPS)/ montmorillonite (MMT) nanocomposites. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) demonstrated that glycerol could enlarge the d‐spacing and destruct the layered structure of MMT effectively during the pre‐processing of MMT. So the enlarged d‐spacing and fragmentized platelets of glycerol activated‐MMT were a precondition to form intercalated or exfoliated TPS‐based nanocomposites during the melt extrusion processing. These highly dispersive and compatible TPS/activated‐MMT nanocomposites had increased thermal stability and tensile properties as compared with non‐activated composites. Especially, the tensile strength of nanocomposites could be enhanced to 8.6 MPa, the improvement was about two times the initial tensile strength of TPS.     

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)。     

Preparation and characterization of bio-nanocomposite films based on soy protein isolate and montmorillonite using melt extrusion

The non-biodegradable and non-renewable nature of plastic packaging has led to a renewed interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanoparticles such as layered silicates). Bio-nanocomposite films based on soy protein isolate (SPI) and montmorillonite (MMT) were prepared using melt extrusion. Effects of the pH of film forming solution, MMT content, and extrusion processing parameters (screw speed and barrel temperature distribution) on the structure and properties of SPI–MMT bio-nanocomposite films were investigated. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were used for structural characterization of the films. Properties of the films were determined by tensile testing, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and water vapor barrier measurement. The arrangement of MMT in the soy protein matrix ranged from exfoliated at lower MMT content (5%) to intercalated at higher MMT content (15%). There was a significant improvement in mechanical (tensile strength and percent elongation at break) and dynamic mechanical properties (glass transition temperature and storage modulus), thermal stability, and water vapor permeability of the films with the addition of MMT. The results presented in this study show the feasibility of using bio-nanocomposite technology to improve the properties of biopolymer films based on SPI.     

Effect of acetylation on the properties of corn starch

Acetylated corn starches with different degrees of substitution (DS 0.85, DS 1.78, DS 2.89) were synthesized by the reaction of corn starch with acetic anhydride in the presence of acetic acid under varying reaction temperatures. The product was characterized by FTIR spectroscopy, ¹H NMR, X-ray diffraction and contact angle measurement. Acid-base titration and ¹H NMR methods were employed to determine the degree of substitution of product. FTIR spectroscopic analysis showed that the characteristic absorption intensities of esterified starch increased with increase in the degree of substitution, and the characterized peak of hydroxyl group almost disappeared in the spectrum of DS 2.89 acetylated starch. The detailed chemical microstructure of native starch and acetylated starch was confirmed by ¹H NMR, ¹³C NMR and ¹³C–¹H COSY spectra. Analysis of ¹H NMR spectra of acetylated starches was assigned accurately. Strong peaks in X-ray diffraction of acetylated starch revealed that new crystalline regions were formed. Compared with native starch, the hydrophobic performance of acetylated starch esters was increased. The contact angle of acetylated starch with DS 2.89 was 68.2°.     

原料和制备方法对醋酸酯淀粉糊化特性的影响

以三种淀粉(马铃薯、木薯和玉米淀粉)为原料,以醋酸酐、醋酸乙烯酯为酯化剂生产醋酸酯化淀粉,对其Brabendar粘度曲线图进行研究。经酯化后,淀粉的糊化特性都有明显的变化(起糊温度降低,粘度增加),但原料和酯化剂的不同,会导致变化程度的不同,另外冷热糊稳定性和凝胶性强弱变化就有更明显的差异。     

不同木薯淀粉对冻融魔芋葡甘聚糖凝胶特性的比较分析

为探究不同木薯淀粉对冻融魔芋葡甘聚糖凝胶的影响,采用木薯淀粉（cassava starch,CS）、木薯醋酸酯淀粉（starch acetate,SA）、木薯乙酰化二淀粉己二酸酯淀粉（acetylated di-starch adipate,ADA）、木薯乙酰化二淀粉磷酸酯淀粉（acetylated di-starch phosphate starch,ADP）四种市售淀粉代替37.5%魔芋葡甘聚糖（konjac glucomannan,KGM）,制备冻融脱乙酰KGM/淀粉复合凝胶。通过质构仪、傅里叶红外光谱仪、热重分析仪、冷场扫描电镜分析其凝胶特性的变化。结果表明,4种木薯淀粉可以改善冻融KGM凝胶的凝胶特性,但不同木薯淀粉间存在差异,KGM/ADP凝胶表现出最优的保水性和热稳定性,与KGM凝胶相比,其析水率从29.75%下降至8.71%,持水率从73.68%提高至87.42%,硬度从274.36 g下降至176.33 g,弹性、内聚性及回复性无显著差异;不同木薯淀粉均未影响葡甘聚糖的脱乙酰行为和结晶形态,但ADP可以改变冻融KGM凝胶微观形貌,提高其抗脱水收缩能力。综合分析,ADP代替部分魔芋葡甘聚糖改善冻融KGM凝胶特性效果最佳,为其在魔芋凝胶食品的应用提供指导。     

The Use of Potato and Sweet Potato Starches Affects White Salted Noodle Quality

ABSTRACT Potato and sweet potato starches and derivatives thereof were used to substitute part of the wheat flour in white salted noodle (WSN) manufacture. The quality of the WSN obtained was compared with the quality of WSN made from wheat flour only. When up to 20% of wheat flour was replaced by acetylated potato starch and acetylated sweet potato starches, the cooking loss of WSN decreased, while the softness, stretchability, and slipperiness increased significantly. Native and hydroxypropylated starches did not exhibit these effects. It can be concluded that the substitution of part of wheat flour with acetylated starches strongly affects noodle-making and final noodle quality, and starch substitution can be used to change the performance of a given wheat flour for noodle making in a desired way.     

乙酰化多孔淀粉吸油性研究

用乙酸酐对多孔淀粉进行乙酰化表面疏水性改良,制得吸油率更高乙酰化多孔淀粉;研究表明,反应体系温度为30℃,pH值为7.0～7.5,乙酸酐加入量为淀粉质量10%,反应时间120min,在此条件下制得乙酰化多孔淀粉吸油率为73.5%,较原多孔淀粉提高20.4%,多孔淀粉经乙酰化后可明显提高其吸油能力。     

Low and high amylose maize starches acetylated by a commercial or a laboratory process both deliver acetate to the large bowel of rats

Short chain fatty acids (SCFA) produced by large bowel bacterial fermentation of carbohydrates promote normal colonic function and health. Previous studies in rats have shown that starches acylated with SCFA to a high degree of substitution (DS) resist small intestinal digestion and pass into the large bowel where the acids are released by bacterial enzyme activity. These studies were conducted with starches manufactured from low or high amylose starches manufactured in the laboratory or commercially. In this study, a direct comparison was made between acetylated low and high amylose maize starch manufactured in the laboratory and high amylose maize starch acetylated commercially. Compared to a standard maize starch, all acetylated starches raised large bowel pools of acetate (by as much as 10-fold) and total SCFA (by between 320% and 775%) when fed to rats. They also raised large bowel digesta mass by as much as 2-fold and lowered pH by up to 28%. These changes were observed when the background diet contained unmodified low or high amylose starch, although the changes were greatest with high amylose maize starch which is consistent with its resistance to digestion. The data confirm that acylated starches are a viable means of raising specific large bowel SCFA, independent of the manufacturing process.     

Characterization of Acetylated Waxy Maize Starches Prepared under Catalysis by Different Alkali and Alkaline‐Earth Hydroxides

The effects of the catalyst used in acetylation, including sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca(OH)₂), on the chemical and physicochemical properties of acetylated waxy maize starch were investigated. The Ca(OH)₂‐catalyzed acetylated starch exhibited a slightly higher pasting temperature and a lower β‐amylolysis limit compared with acetylated starch prepared under NaOH or KOH catalysis, but no difference was observed for their thermal properties. The carbohydrate profiles of isoamylase‐debranched acetylated starches and their β‐limit dextrins were characterized by high‐performance size‐exclusion chromatography. The Ca(OH)₂‐catalyzed acetylated starch showed a elution profile that was different from those of the other two acetylated starches with a greater proportion of saccharides eluted at a longer retention time. However, the differences in pasting temperature, β‐amylolysis limit, and carbohydrate profile among the acetylated starches diminished when ethylenediaminetetraacetic acid (EDTA) was added. The results suggest that calcium might induce intermolecular crosslinking through chelation with oxygen of the anhydroglucose units and this type of crosslinking was promoted in acetylation catalyzed by Ca(OH)₂.     

Functional and dynamic rheological properties of acetylated starches from two cultivars of cassava

The starches derived from two different cultivars of cassava were modified with acetic anhydride. The increase in swelling power and solubility of the cassava starch (CS) pastes treated with different acetic anhydride concentration could be attributed to easier hydration, resulting from reduction of interaction between starch chains due to the substitution. The transition temperatures (T_o, T_p and T_c) and enthalpy of gelatinisation (ΔH) of acetylated CS, were determined. The values were lower than those of native starches. Rheological properties of CS pastes (5% w/w) as a function of the degree of substitution were evaluated in dynamic shear force measurements. Magnitude of storage modulus (G′), loss modulus (G′′) and complex viscosity (Eta*) of acetylated CS pastes were determined also. Dynamic moduli (G′, G′′ and Eta*) values of acetylated sweet cultivar pastes were generally higher than those of native starch whereas the acetylated samples of the bitter cultivar were lower than those of native starch. The magnitudes of G′ were greater than those of G′′ and Eta* at all frequencies (ω). The fact that all the tan δ (ratio G′′/G′) values (0.7–0.48 and 0.25–0.44) were less than one is an indication that the samples are more elastic than viscous. The acetylated starches could find promising industrial uses in food products like Lemon curd and Mayonnaise and other non‐food applications.     

乙酰化马铃薯微晶淀粉的制备及性能

为改善马铃薯淀粉性能,拓宽其应用领域,对马铃薯淀粉进行微晶化和乙酰化复合改性。本文以马铃薯淀粉为原料、盐酸为酸解剂、醋酸酐为乙酰化试剂、氢氧化钠为催化剂对乙酰化马铃薯微晶淀粉的制备和性能进行了研究。结果表明:马铃薯淀粉经微晶化及乙酰化后,其抗酸性、抗碱性和冷热黏度稳定性增强,但其凝沉性、冻融稳定性、蓝值和起始分解温度降低。马铃薯微晶淀粉结构为B型,乙酰化对马铃薯淀粉微晶结构有影响。     

具有不同微结构的壳聚糖/淀粉复合材料的性能及其应用

本文选择4种具有不同微结构的壳聚糖,与淀粉形成复合材料,并对复合溶液的流变、粘弹性能以及复合薄膜的机械性能进行探讨,利用复合材料对含药片剂进行薄膜包衣,考察其控释性能。实验结果发现,壳聚糖/淀粉复合溶液具有假塑性流体特征,壳聚糖粘均分子量越大,剪切稀化现象越明显。同时,在复合薄膜制备过程中,壳聚糖可促进淀粉分子链的排布,提升复合薄膜的抗拉强度、断裂伸长率,调控壳聚糖微观结构可改善复合薄膜的机械性能。当包衣片剂运转至模拟肠液,借助壳聚糖上的-NH_3~+与淀粉的-OH间的氢键作用,片剂外可形成凝胶层,阻碍药物的释放,壳聚糖分子量越大,药物从复合薄膜包衣片剂中释放的累积量越小。以粘均分子量2.543×10~5 g/mol的壳聚糖CTS60与玉米淀粉制备的复合薄膜包衣片剂,约有70.59%药物可递送至肠道,其中有21.83%释放于模拟小肠,48.77%释放于模拟结肠,表现出一定的控释性能。     

Effect of Type and Content of Modified Montmorillonite on the Structure and Properties of Bio-Nanocomposite Films Based on Soy Protein Isolate and Montmorillonite

Abstract: The nonbiodegradable and nonrenewable nature of plastic packaging has led to a renewed interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanoparticles such as layered silicates). Bio-nanocomposite films based on soy protein isolate (SPI) and modified montmorillonite (MMT) were prepared using melt extrusion. The effect of different type (Cloisite 20A and Cloisite 30B) and content (0% to 15%) of modified MMT on the structure (degree of intercalation and exfoliation) and properties (color, mechanical, dynamic mechanical, thermal stability, and water vapor permeability) of SPI-MMT bio-nanocomposite films were investigated. Extrusion of SPI and modified MMTs resulted in bio-nanocomposites with exfoliated structures at lower MMT content (5%). At higher MMT content (15%), the structure of bio-nanocomposites ranged from intercalated for Cloisite 20A to disordered intercalated for Cloisite 30B. At an MMT content of 5%, bio-nanocomposite films based on modified MMTs (Cloisite 20A and Cloisite 30B) had better mechanical (tensile strength and percent elongation at break), dynamic mechanical (glass transition temperature and storage modulus), and water barrier properties as compared to those based on natural MMT (Cloisite Na⁺). Bio-nanocomposite films based on 10% Cloisite 30B had mechanical properties comparable to those of some of the plastics that are currently used in food packaging applications. However, much higher WVP values of these films as compared to those of existing plastics might limit the application of these films to packaging of high moisture foods such as fresh fruits and vegetables.     

Effect of Glycerol on Water Vapor Sorption and Mechanical Properties of Starch/Clay Composite Films

Plasticized starch/clay composite films were prepared by casting aqueous solutions containing oxidized corn starch, different concentrations of glycerol as a plasticizer and 5% clay (sodium montmorillonite, Na⁺‐MMT) on the basis of dry starch. The water‐binding properties of the composite films were evaluated by water vapor sorption isotherms at room temperature and various relative humidities (RHs). Mechanical properties and abrasion resistance were also analyzed for the films with varying glycerol contents at 68% RH and room temperature. Changes in water sorption isotherms suggested that glycerol interacted with both water and starch in a complicated way. A saturation phenomenon of glycerol, depending on RH, was observed based on the isotherms. Above this saturation content, phase separation of the system occurred with the appearance of free glycerol. According to mechanical performance and abrasion resistance, as well as water vapor sorption of the starch blend films, the three‐stage transition was presented to be related to the state of glycerol in the blend system, i.e. adsorption of glycerol onto H‐bonding sites of starch, supersaturation of glycerol as plasticizer and further supersaturation of glycerol. Only above the supersaturation content can glycerol play a plasticizer role in starch‐based composites.     

乙酰化淀粉/PBS制备生物降解塑料的研究

以玉米淀粉为原料,以醋酸酐为乙酰化试剂,氢氧化钠为催化剂,利用微波辐射技术制得乙酰化淀粉。用制备的乙酰化淀粉与聚丁二酸丁二醇酯(PBS)共混,制备了可生物降解热塑性淀粉塑料。研究了共混物制备的最佳工艺条件及其力学性能、生物降解性能及吸水性能,并对产物进行了红外光谱结构分析和表面电镜扫描分析。     

复合氧化剂法合成氧化玉米淀粉

以玉米淀粉为原料,过氧化氢和过硫酸钾为复合氧化剂,Fe~(2+)为催化剂,在酸性条件下以湿法工艺合成氧化玉米淀粉。以淀粉质量分数、复合氧化剂比例、复合氧化剂质量分数(占干淀粉总量)、催化剂质量分数(占干淀粉总量)、反应温度、反应时间等因素为变量,以羧基含量作为氧化度衡量指标,采用单因素试验和正交优化试验,确定制备氧化玉米淀粉最佳工艺条件为:淀粉质量分数35%、复合氧化剂质量分数8%、复合氧化剂比例[m(H_2O_2):m(K_2S_2O_8)]为4:1、体系pH 4.00、催化剂质量分数0.3%、反应温度50℃、反应时间1.5 h,在此条件下,可合成氧化度为0.118%氧化玉米淀粉。     

Dynamic Rheological and Thermal Properties of Acetylated Sweet Potato Starch

Dynamic rheological and thermal properties of acetylated sweet potato starch (SPS) pastes (5%, w/w) were evaluated as a function of the degree of substitution (DS). The transition temperatures (T_o, T_p and T_c) and enthalpy of gelatinization (ΔH) of acetylated SPS, which were determined using differential scanning calorimetry, were lower than those of native starch, and significantly decreased with an increase in DS. Magnitudes of storage modulus (G′), loss modulus (G′′) and complex viscosity (η*) of acetylated SPS pastes were determined using a small‐deformation oscillatory rheometer. Dynamic moduli (G′, G′′ and η*) values of acetylated SPS pastes except for 0.123 DS were higher than those of native starch, and they also decreased with an increase in DS. The tan δ (ratio of G′′/G′) values (0.37–0.39) of acetylated SPS samples were lower than that (0.44) of native starch and no significant differences were found among acetylated SPS samples, indicating that the elastic properties of SPS pastes were affected by acetylation but did not depend on DS. The G′ values of acetylated SPS during aging at 4°C for 10 h were much lower than those of native starch, showing that the addition of acetyl groups produced a pronounced effect on the retrogradation properties of SPS.     

酸解淀粉/PBAT复合膜的制备及其性能研究

为了提高淀粉基复合膜的力学性能和阻水性能,以酸解淀粉和聚己二酸-对苯二甲酸丁二醇酯（PBAT）为主要成膜基材,通过挤出吹塑法制备了酸解淀粉/PBAT复合膜,研究了淀粉/PBAT比例对复合膜结构、力学性能和阻隔性能等的影响。结果表明,随着PBAT含量的增加,淀粉/PBAT共混物的流动性增强,模量与复合黏度降低,淀粉与PBAT之间的氢键作用减弱。添加PBAT可显著提高淀粉膜的力学性能和阻隔性能,复合膜纵向最大拉伸强度和断裂伸长率分别为7.86 MPa和532.67%,最低水蒸气和氧气透过系数分别为3.74×10?11 g?m?1?s?1?Pa?1和5.77×10?15 cm2?s?1?Pa?1。     

不同变性淀粉对冷冻面团热力学特性的影响

采用差示扫描量热法(DSC)研究4种不同种类变性淀粉对冷冻面团热力学特性(玻璃化转变温度、冰晶融化特性和可冻结水含量)的影响。结果表明,冷冻面团的玻璃化转变温度在-30℃左右,不同变性淀粉对冷冻面团玻璃化转变基本无明显影响;添加5%马铃薯羟丙基淀粉、木薯羟丙基淀粉和木薯醋酸酯淀粉可以显著降低冷冻面团冰晶融化范围,面团中形成的冰晶大小更加均匀;冷冻面团可冻结水含量随着马铃薯醋酸酯淀粉和马铃薯羟丙基淀粉添加量的增加呈降低趋势,添加10%木薯羟丙基淀粉时,面团可冻结水含量显著低于空白组,而木薯醋酸酯淀粉对面团可冻结水含量无显著影响。