微细化玉米淀粉粒度效应及其流变学行为研究

采用现代粉体机械可制备微细化玉米淀粉。随着淀粉粒度减小,其支链淀粉和直链淀粉糊的特性黏度降低,分子量下降。布拉班德黏度分析表明,微细化玉米淀粉糊化起始温度下降,热糊稳定性增强;在冷却阶段,随着粒度降低,微细化玉米淀粉的凝沉性较原玉米淀粉增强,冷糊稳定性较原玉米淀粉减弱。微细化玉米淀粉糊为非牛顿假塑性流体,其流动性随粒度降低而增加,并显示出一定的粒度效应。     

酶对淀粉颗粒相变性质的影响

采用差示扫描量热仪和Brabender连续黏度仪,系统研究了淀粉颗粒经中温液化酶、葡萄糖淀粉酶和真菌糖化酶作用后的相变性质变化规律。结果表明,随着淀粉酶水解率的提高,淀粉颗粒起始温度、峰值温度、终点温度和吸热焓都呈先上升后小幅下降的趋势,但中温液化酶作用后的吸热焓先降低后上升,说明中温液化酶在较低水解率下作用淀粉颗粒的无定形区的同时也作用结晶区,而葡萄糖淀粉酶和真菌糖化酶主要作用淀粉颗粒的无定形区。连续黏度分析表明,与原玉米淀粉比较,酶处理淀粉糊的峰值黏度均呈下降趋势,起始糊化温度和峰值温度呈上升趋势。     

短直链淀粉纳米颗粒涂层制备超亲水淀粉膜

采用蜡质玉米淀粉为原料,经普鲁兰酶脱支处理,制备短直链淀粉.将短直链淀粉糊化后的溶液,通过膜材浸泡的方式,使淀粉膜表面形成短直链淀粉涂层,再通过4℃的老化处理,制备超亲水淀粉膜.对超亲水淀粉膜的表面形貌、结晶结构、红外光谱及亲水性进行了研究.结果表明,短直链淀粉在淀粉膜表面自组装成了纳米颗粒结构,增加了膜材表面的粗糙度,改善了淀粉膜的亲水性能.当短直链淀粉溶液质量浓度为0.010 g/mL时,可获得水接触角接近于0°的超亲水淀粉膜.     

酸解工艺对玉米淀粉糊化性能的影响

以玉米淀粉为原料,用盐酸对其酸解制备酸解玉米淀粉。采用正交试验方法,研究了盐酸浓度、淀粉乳浓度、反应温度和反应时间对酸解玉米淀粉糊化性能的影响,优化了酸解工艺。结果表明,盐酸浓度和反应温度的变化对酸解玉米淀粉糊化黏度和糊化温度的影响显著;盐酸浓度、反应时间和淀粉乳浓度的变化对酸解玉米淀粉的糊化焓影响显著。     

高直链玉米淀粉可食性膜的研制

随着科技的进步,膜包装技术在食品工业得到了飞速发展,但同时伴随"白色污染"问题.为了减少环境污染,选用了可再生的、可食用的高直链玉米淀粉为原料,主要研究了甘油用量、糊化方法、糊化时间、烘干温度以及羧甲基纤维素钠对成膜性质的影响.试验结果表明,高直链玉米淀粉可食性膜最佳成膜工艺参数为甘油用量1mL,羧甲基纤维素钠用量为0.1g,121℃糊化30min,干燥温度为90℃.     

微细化处理玉米淀粉对糊化温度及粘度的影响

目的对比、分析不同研磨介质条件下研磨所得玉米淀粉糊化温度和峰值粘度的变化。方法采用行星式球磨机对玉米淀粉进行微细化处理,分别以无介质、蒸馏水和无水乙醇等为研磨介质对淀粉进行研磨,用淀粉粘度测定仪测定研磨所得淀粉的糊化温度及峰值粘度。结果研磨所得玉米淀粉糊化温度和峰值粘度均随研磨时间的延长而下降。研磨介质对玉米淀粉糊化温度的影响为蒸馏水无水乙醇未添加介质;研磨介质对玉米淀粉峰值粘度的影响为蒸馏水无水乙醇未添加介质。结论球磨能够降低玉米淀粉的糊化温度和峰值粘度,研磨介质为蒸馏水时淀粉性质变化最大。     

高直链淀粉材料改性及应用研究进展

目的高直链淀粉具有独特的糊化特性和优异的成膜性能,在可降解材料和包装领域有较大的应用前景,但高直链淀粉基可降解材料耐水性差,湿强度低是一直以来固有的缺陷,因而需要充分了解高直链淀粉基材料的广泛应用,深入探索高直链淀粉的改性方法。方法通过追踪国内外高直链淀粉相关的改性研究和应用进展,概述高直链淀粉的基本性质和性能,重点分析高直链淀粉常用的改性方法,如物理改性、化学改性和酶改性对高直链淀粉微观结构和力学性能的影响,详细介绍高直链淀粉在众多领域的挑战与机遇。结论通过物理改性、化学改性和酶改性等方法,可以实现高直链淀粉粒径减小、糊化温度降低、热稳定性提高等理化性质的改善,拓宽了高直链淀粉在包装、食品和医用等领域的应用范围。     

取代基团在变性淀粉颗粒中的分布

详细论述了取代基团在变性淀粉颗粒表面和内部、结晶区和无定形区、支链和直链上分布的研究原理和方法,认为变性基团可能优先分布在颗粒的无定形区域,但当反应条件十分苛刻时也能进入颗粒的结晶区域;变性优先发生在颗粒的表面,也会在颗粒的内部发生,表面的取代度是整个淀粉颗粒平均取代度的3~4倍;变性既可以发生在直链淀粉又可以发生在支链淀粉的非还原端和分支点周围,并且直链淀粉的取代程度比支链淀粉要高。     

反应温度和时间对干法制备马来酸酐酯化淀粉性能的影响

采用干法制备马来酸酐酯化淀粉,研究了反应温度和时间对酯化淀粉性能的影响。采用红外光谱(FT-IR)证明了马来酸酐成功酯化到淀粉上。利用化学滴定法、X射线衍射(XRD)、差示扫描量热法(DSC)和热重分析(TGA)对酯化淀粉的取代度、结晶结构、糊化温度和热稳定性进行了分析。结果表明,随着反应温度升高和时间延长,取代度逐渐增大。酯化反应一定程度上破坏了淀粉的结晶结构,随反应温度升高和反应时间延长,结晶度逐渐降低。糊化温度和热稳定性跟酯化淀粉的结晶度密切相关,结晶度降低,糊化温度和热稳定性都逐渐降低。     

热塑性淀粉片材的制备及性能研究

利用双螺杆挤出机对玉米淀粉进行糊化处理,经干燥、粉碎后制得预糊化淀粉,以其为原料,添加甘油,PVA为增塑剂制备热塑性淀粉,经模压制备片材后,通过偏光显微镜分析了淀粉的糊化情况,研究了甘油含量和PVA含量变化对材料性能的影响。实验结果表明:甘油含量的增加会降低片材的抗拉强度,但升高其断裂伸长率;而增加了PVA的含量,材料抗拉强度和断裂伸长率均呈增长趋势。     

糯米的湿热处理及其结构表征

目的为了解决新糯米制粉峰值粘度过低的问题。方法对糯米进行湿热处理,研究糯米含水量、湿热处理时间和温度对糯米粉粘度等糊化特性的影响,并进行响应面优化。结果得到了湿热处理的最佳工艺条件,温度为70℃,含水量(质量分数)为20%,时间为1.6 h,在此工艺条件下糯米粉的峰值粘度为3.146Pa·s,与原糯米粉相比增加了37.3%,且谷值粘度、最终粘度和崩解值均增加。差示扫描量热仪分析表明,湿热处理后糊化温度有所升高,热焓值无显著性变化。X-衍射图谱表明,结晶度变化不大,且糯米淀粉晶型仍呈A型。通过扫描电镜观察,湿热处理后糯米淀粉粒的表面出现部分孔洞、凹陷和粘结等现象,整体形貌未发生显著变化。结论该工艺能够大幅度提升糯米粉的峰值粘度。     

Evaluation of the emulsifying properties of some cationic starches

Different cationic potato, maize, and waxy maize starches were evaluated for their emulsifying properties. Emulsions were prepared using 20% (w/w) arachidic oil and 80% (w/w) water. Emulsions with the cationic starches as emulsifier in a concentration ranging from 1% to 5% (w/w) were prepared and characterized by droplet size and viscosity measurements, and the stability was evaluated visually and by electrical conductance measurements. None of the cationic potato, waxy maize starches, and maize starches with a low degree of substitution (DS) showed adequate emulsifying properties. Emulsions prepared using non-pregelatinized (C ☆ bond 05914, 2% and 5% w/w; C ☆ bond 05907, 5% w/w) and pregelatinized (C ☆ bond 12504, 5% w/w) cationic maize starches with high-DS were visually stable. The initial mean droplet volume diameter of the emulsions prepared with these cationic starches in a 5% (w/w) concentration was similar and ranged from 2.40 to 2.84 μm however, there was an important difference in droplet size distribution. The droplet size distribution of the emulsions prepared using the non-pregelatinized high-DS cationic starches was markedly narrower than in the case of the emulsions prepared using the pregelatinized high-DS cationic starches. The droplet size of the emulsions remained almost constant during 120 days of storage. Visual inspection and electrical conductance measurements showed that these emulsions were stable for at least 120 days.     

超声波处理对蜡质玉米淀粉糊流变性质的影响

研究了超声波处理前后蜡质玉米淀粉的流变性质变化。采用超声波对含水量70%的蜡质玉米淀粉进行处理,运用旋转黏度计对处理前后的淀粉糊特性进行研究。结果表明,不同超声功率处理的蜡质玉米淀粉糊均为假塑性流体;超声处理的蜡质玉米淀粉糊表观黏度随剪切速率的升高而降低,随着体系浓度增高,剪切稀化增强;超声处理的淀粉糊其触变性随超声功率的增大而减小。     

抗性糊精对面粉流变特性及糊化凝胶的影响

目的 为扩大抗性糊精在面制品中应用，探究抗性糊精对面粉品质特性的影响。方法 将抗性糊精按照不同质量分数(2.5%~10%)添加到面粉中，采用粉质、拉伸仪分别考察抗性糊精对面粉流变特性的影响，并通过RVA糊化仪和扫描电镜等手段探究面粉糊化及凝胶特性的影响。结果 与对照组相比，添加抗性糊精能使面粉稳定时间显著延长和弱化度显著降低，改善面团整体的拉伸特性，提升面粉筋力;糊化黏度特性显示，抗性糊精能提升面粉的糊化温度，使面粉的糊化峰值黏度、崩解值和回生值降低，改善面粉糊化热稳定性，并延缓凝胶短期回生。结论 抗性糊精可作为面粉改良剂，改善面粉流变、糊化及凝胶回生特性，从而提升面粉的品质。     

Crosslinked Starch as Sustained Release Agent

Different types of crosslinked starches and pregelatinized-crosslinked starches were evaluated for their use as hydrophilic matrices. Some fundamental properties of these chemically modified starches, e.g. granule swelling power and viscosity of the dispersion in function of pH and ionic strength, were studied. Dissolution tests and the rate and amount of water uptake were evaluated on tablets containing theophylline and modified starch (40/60 w/w), compressed on an instrumented tablet press at three different pressures (50,200 and 300 MPa.). Theophylline releasing profiles were determined using the paddle system at a rotational speed of 50 rpm Water, simulated gastric fluid, and simulated intestinal fluid were used as dissolution media. Crosslinked starches showed a poor swelling power and dispersion viscosity in comparison to pregelatinized starch and pregelatinized-crosslinked starches. The pregelatinized-crosslinked starches developed less swelling power than the pregelatinized starch, but they showed higher dispersion viscosity than the pregelatinized starch. The viscosity of all starch dispersions was not affected by ionic strength. An alkaline pH dramatically increased the dispersion viscosity of pregelatinized starch and pregelatinized-crosslinked starches. Drug dissolution rate was lower for tablets containing pregelatinized starch than for tablets containing pregelatinized-crosslinked starches. This phenomenon can be related to the rate and amount of water uptake. The dissolution rate seemed not to be influenced by the compression force nor by the composition of the dissolution media. The results indicate that crosslinked starches, either pregelatinized or not, are not suitable as sustained release agents.     

不同氧化条件下氧化马铃薯淀粉胶粘剂影响因素的研究

选用马铃薯淀粉为原料,双氧水为氧化剂,以淀粉用量、氧化剂用量、反应温度、反应时间和pH值为影响因素,按L25(56)正交实验表分别在一般氧化和高氧化条件下制备2组氧化淀粉,然后再配成胶粘剂,测定了粘度、快干性、耐水性,最后通过分析和讨论,总结出了在2种氧化条件下各正交因素对胶粘剂相关性能的影响规律,寻求到了性能相对较佳的氧化淀粉反应条件和配方.     

Rheology and flow-induced liquid crystal phase transitions in thermotropic polyethers

This work investigates the interdependence of the phase behaviour, viscosity, temperature, molecular weight and shear rates of thermotropic liquid crystalline polyethers. The viscosity of the isotropic and nematic phases are quantitatively compared; a positive variation in viscosity with respect to temperature is found, with the isotropic viscosity being about an order of magnitude higher than the liquid crystalline viscosity. The dependence of viscosity upon molecular weight of well defined fractions is investigated in both the liquid-crystal and isotropic phases. In the liquid crystalline state the viscosity scales with M ^3.5–5. Variations in the viscosity due to temperature changes affect the isotropic phase more than the liquid crystal phase. No evidence for a negative first normal stress difference is seen. Finally, it is shown how the phase diagram of the material can be altered by shearing the material in the isotropic phase. This is evident by the onset of a shear thinning region at temperatures slightly above T _i, which can be attributed to the formation of shear induced liquid crystallinity.     

PVDF、LCP及其共混物的流变行为

研究了ＰＶＤＦ、ＬＣＰ的表观粘度随温度,剪切速率的变化规律,并对液晶含量对共混物熔体度的影响进行了讨论。     

Green isolation and physical modification of pineapple stem waste starch as pharmaceutical excipient

The waste of inedible parts of pineapple, particularly in tropical countries, contributes to environmental burden. This study aimed to utilize pineapple stem waste as a source of starch-based pharmaceutical excipient. The starch was isolated from pineapple stem waste using a simple process without applying harsh chemicals. The isolated starch (PSS) was then physically modified through gelatinization and spray drying to improve its physical properties. Starch characteristics were identified by FTIR, TGA, and XRD analysis. The SEM imaging showed morphological change with reduced surface roughness due to physical modification of the starch. Decreased crystallinity of modified starch (MPS) was confirmed by our XRD results: the peaks of A-type crystalline at 2θ of 13°, 15°, 18°, and 23° were present in PSS, yet mostly absent in MPS. Thermogravimetric analysis showed that MPS behaved differently from PSS and the degradation events occurred at lower temperature. When the starch was spray-dried without prior gelatinization process, the physicochemical characteristics of spray-dried starch resembled untreated starch. Moisture content in PSS (10.66%) decreased after gelatinization to 7.3%. Potential use of MPS was demonstrated by its powder flowability (Student’s t test, p?<?0.05), swelling capacity (Student’s t test, p?<?0.05), and compaction profile. In summary, our findings demonstrated that modified pineapple starch showed better physical characteristics and quite promising as a tablet binder and disintegrant.     

Blending of modified polyphenylene ether with a liquid crystalline copolyester

Blending of poly (2,6-dimethylphenylene ether) (PPE), polystyrene (PS) and a thermotropic liquid crystalline polymer (LCP) was performed using a continuous co-rotating twin-screw extruder. The influence of LCP content on the blending process was studied by changing the barrel heater temperature and the screw speed. The torque of the screw shafts generated during the blending process was influenced by LCP content; its influence was not simple. The generated torque was found to depend not only on the melt viscosity of LCP but also on its distortion temperature. Further, the effects of matrix viscosity on the morphology and mechanical properties of the PPE/PS/LCP blends were studied. Well-developed fine LCP fibrils were formed during the melt-drawing process when the matrix viscosity was high. The formation of well-developed fine fibrils was found to improve the mechanical properties of the PPE/PS/LCP blend. Two mechanisms are proposed for the formation of well-developed fine LCP fibrils.