Quantitative analysis of amylopectin unit chains by means of high-performance anion-exchange chromatography with pulsed amperometric detection

High-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC–PAD) is a widely used technique to study the chain length distribution of amylopectin. The chromatograms, however, do not directly reflect this distribution, since the PAD response changes with the degree of polymerization. In this study, waxy maize starch was debranched and fractionated on a Bio-Gel P-6 column and the response factors for maltosaccharides with DP 3–65 were determined. The detector response per μg glucan chains was shown to decrease considerably for DP 3–7 while the curve leveled out for DP larger than 15.     

Studies on the properties and characteristics of starch-LDPE blend films using cross-linked, glycerol modified, cross-linked and glycerol modified starch

Corn starch was modified by cross-linking with epichlorohydrin and plasticizer glycerol. X-ray diffraction studies showed that relative crystallinity of the native and cross-linked starch were similar and were not affected by cross-linking. Different films were prepared by blending corn starch, cross-linked starch or glycerol modified starch in LDPE. The mechanical properties of the films were studied for tensile strength, elongation, melt flow index, and burst strength. The properties of the blend films were compared with LDPE films. It was observed that with the blending of 7.5% native starch, there was a decrease in tensile strength, elongation and melt flow index but burst strength increased. The tensile strength, elongation and melt flow index of the films containing cross-linked starch was considerably higher than those containing native starch but the burst strength showed a reverse trend. For native starch and cross-linked starch modified with glycerol, the elongation and melt flow index of the films increased but burst strength decreased. Surface scanning of the blend films were done by scanning electron microscope. Film containing cross-linked starch/glycerol modified starch in the blend was observed to be smoother than the native starch blend films.     

Barrier and mechanical properties of modified starches

The study addressed starch-based coatings on paper and fabrics. Coated materials and free starch films containing different amounts of a well-established plasticizer (glycerol) or potential plasticizer (mainly polyols) were tested with respect to water vapour permeance (WVPe), water vapour permeability (WVP), glass transition temperature (T_g), and mechanical strength (tensile tests). Both normal and high- amylose potato starch were used. These starches were modified by (a) oxidation, (b) oxidation and hydroxypropylation or (c) oxidation and hydrophobically modified by reaction with octenyl- or alkenyl-substituted succinic acid anhydride. Free films of hydroxypropylated high-amylose potato starch showed a lower WVP than did the corresponding starches based on regular potato starch. The WVP of the hydrophobically modified regular potato starches was substantially higher than that of films of the corresponding hydroxypropylated starches. The expected hydrophobic effect of the succinic acid anhydrides in terms of a reduced WVP could not be observed. When glycerol was used as a plasticizer, about 30 parts (by wt.) per hundred parts of starch were needed in order to reduce the T_g and to cause observable changes in the mechanical properties of the free films.     

Role of solvation energy in starch adsorption on oxide surfaces

The effect of potassium and sodium cations on the adsorption of starch onto hematite and quartz was investigated. The role of these ions was analyzed in terms of their water structure-making or -breaking capabilities. In the presence of Na⁺, a structure maker, the polymer adsorption density did not change compared to the adsorption levels observed in distilled water. However, in the solutions of K⁺, a structure-breaking cation, the adsorption density of starch significantly increased. Assuming hydrogen bonding and chemical interaction to be the driving adsorption mechanism, it was proposed that the starch–oxide interactions can be envisioned as the competition between chemical interaction/hydrogen bonding and solvation energy:

K⁺ reduces solvation energy by disturbing interfacial water structure and thus increases the free energy of adsorption, allowing the polymer to more closely approach the oxide surfaces. In contrast, Na⁺ which is indifferent to solvation energy does not interfere with the free energy of adsorption.     

In situ thermal decomposition of starch with constant moisture in a sealed system

This paper reports a DSC study of the thermal decomposition of starch kept at constant moisture content (0-50%) in a sealed system comprising a high-pressure stainless steel pan with a gold-plated copper seal. The advantage of this technique is that it facilitates the detection and study of the processes of thermal decomposition of starch with constant moisture content, which is a common scenario in the processing of thermoplastic starches. It was found that the decomposition temperature decreased with increasing water content, and that the peak in decomposition temperature broadened, which is different to the case observed in open, unsealed systems.     

Enzymatic degradation of some nanocomposites of poly(vinyl alcohol) with starch

A study of the enzymatic degradation of some montmorillonite-containing nanocomposites of poly(vinyl alcohol) with starch was based on the determinations of mass loss and the reducing sugars. The degraded residues have been examined by FT-IR spectroscopy and optical microscopy. It has been established that the nanoparticles hinder degradation, while the susceptibility to enzymatic degradation varies in the order: PVA/starch/nanocore > PVA/starch/Bentonite > PVA/starch/Peruvian clay.     

Microwave-Assisted Synthesis and Characterization of Polyurethanes from TDI and Starch

In this work, a microwave-assisted method was developed to prepare polyurethanes from starch or maltodextrin and tolylene-2,4-diisocyanate (TDI). As compared to conventional heating, this new synthetic procedure saves energy, significantly reduces reaction time, and yet entails product yields that are comparable to those of the conventional heating procedure. The reaction products were characterized with NMR, FT-IR, thermogravimetric analysis, and scanning electron microscopy. From these analyses, the polyurethanes made with the conventional and microwave methods are shown to be similar in chemical structure and physical morphology. Furthermore, the ¹H and ¹³C NMR spectra of the starch polyurethanes have been fully assigned for the first time.     

淀粉悬浮液荧光光谱特性的研究

为实现淀粉接枝共聚反应的随时检测监控及自动控制,以反应中产生的自由基具有发光特性为着眼点,研究淀粉悬浮液在紫外激励下产生的荧光光谱及其特性,可对淀粉接枝共聚反应中自由基的产生、发光和消失的特点及机理的探索提供理论和实验上的参考。实验结果表明：淀粉悬浮液在260～280 nm的紫外光激励下,发射峰值波长在339 nm左右。理论分析表明, 淀粉分子环结构中醚键C—O—C的氧未共键电子吸收激发光子产生n→σ*跃迁后,发射出荧光。     

CoW11Ti/淀粉纳米复合物的合成与表征

近年来, 多酸化合物的生物活性及药物性质研究十分活跃[1], 有些多酸化合物已作为抗HIV病毒及抗肿瘤药物应用于临床或进入临床研究[2,3]. 但由于它们的毒副作用大, 在水中稳定存在的pH值范围小, 在体内易分解, 故研究尚无突破性进展[1].     

Characterization of Full—Biodegradable Starch—PVA—Polyester Film

IntroductionConventional polymers such as polyethyleneand polypropylene persistfor many years after landdisposal.Furthermore,plastics are often soiled byfood and other biological substances,making phys-ical recycling of those materials impractical andgenerally undesirable. In contrast,biodegradablepolymers disposed in bioactive environment are de-graded by the enzymatic action of microorganismssuch as bacteria,fungi,and algae.The worldwideconsumption of biodegradable polymers increasedfrom 1 .…