The ex-situ and in-situ ultrasonic assisted oxidation of corn starch: A comparative study

The objective of this study was to evaluate the differences in ex-situ (starch treated by ultrasonication and oxidation sequentially, U-OS) and in-situ (starch treated by ultrasonication and oxidation simultaneously, UOS) ultrasonic assisted oxidation process of corn starch, which were studied in contrast to the traditional oxidized starches (OS). Fourier-transform infrared spectra confirmed the successful oxidation of all modified starches samples. In comparison to the OS, the carboxyl contents of U-OS and UOS increased by 56% and 112%, respectively. The same increase trend was also found for the carbonyl contents. The significance raise was attributed to the great increase of pores and specific surface areas in the starch granule after ultrasonic irradiation which promoted the penetration of the sodium hypochlorite into the starch granules with higher chances for chemical reactions. SEM and pore size distribution characterizations further verified this result. However, the method of in-situ ultrasonic assisted oxidation can simultaneously accelerate the increase of pores and the penetration process. Consequently, the starches with higher oxidation degree can be more efficiently prepared by the strategy of in-situ ultrasonic assisted oxidation.     

Silylation of Cellulose and Starch – Selectivity, Structure Analysis, and Subsequent Reactions

The silylation of cellulose and starch under different starting conditions is reviewed. The control of the degree of substitution (DS) and regioselectivity in dependence of the reaction pathway are discussed in detail. The synthesis of trimethylsilyl cellulose (TMSC) in the system hexamethyldisilazane (HMDS)/ammonia leads to partially and completely silylated products controlled by the amount of the components. Hydrolytic desilylation of TMSC in tetrahydrofuran (THF)/ammonia gives the partially desilylated products. The desilylation proceeds statistically along the polymer chains. The reaction of cellulose dissolved in N,N-dimethylacetamide (DMA)/LiCl with bulky thexyldimethylchlorosilane (TDSCl) in the presence of imidazole leads to 2,6-di-O-TDS cellulose. The silylation of starch dissolved in dimethylsulfoxide (DMSO) with TDSCl/pyridine results in the formation of regioselectively 2-O and 6-O functionalized silyl ethers with DS values up to 1.8. 6-O Silyl ethers of cellulose and starch were synthesized with TDSCl highly activated in the reaction system N-methylpyrrolidone (NMP)/ammonia. Two- dimensional NMR techniques after subsequent modifications of the remaining OH groups have been established as important methods for the characterization of the substitution pattern of the described silyl ethers. In the case of starch, the distribution of the substituents could be detected not only in the anhydroglucose units (AGU) but also in the non-reducing end groups (NEG).     

A new potentiometric sensor for the determination of α-amylase activity

A platinum redox sensor for the direct potentiometric determination of α-amylase concentration has been described. The sensor measured the amount of triiodide released from a starch-triiodide complex, which was correlated with the α-amylase activity after biocatalytic starch degradation. The composition and stability of the potassium triiodide solution was optimized. The starch-triiodide complex was characterized potentiometrically at variable starch and triiodide concentrations. The response mechanism of the platinum redox sensor towards α-amylase was proposed and the appropriate theoretical model was elaborated. The results obtained using the redox sensor exhibited satisfactory accuracy and precision and good agreement with a standard spectrophotometric method and high-sensitive fully automated descret analyser method. The sensor was tested on pure α-amylase (EC 3.2.1.1, Fluka, Switzerland), industrial granulated α-amylase Duramyl 120 T and an industrial cogranulate of protease and α-amylase Everlase/Duramyl 8.0 T/60 T. The detection limit was found to be 1.944 mU for α-amylase in the range of 0-0.54 U (0-15 μg), 0.030 mKNU for Duramyl 120 T in the range of 0-9.6 mKNU (0-80 μg) and 0.032 mKNU for Everlase/Duramyl 8.0 T/60 T in the range of 0-9.24 mKNU (0-140 μg).     

Aliphatic polyester-grafted starch composites by in situ ring opening polymerization

Catalyzed Ring-Opening Polymerization (ROP) of lactones, such as ε-caprolactone and δ-valerolactone, has been investigated for preparing aliphatic polyester-grafted corn starch compositions. The polymerization has been carried out either in bulk (without solvent) or in 10 wt% granular starch in toluene suspension, after adequate activation of the starch surface amylose/amylopectin hydroxyl groups into aluminum alkoxides. This activation has been done by in situ reaction with triethylaluminum and has proved to be very effective in promoting fast ROP and also covalent grafting of the polyester chains onto the starch surface. Drying of the starch granules constitutes a key-step of the proposed process. The actual fixation of the initiator onto the starch surface has been checked by XPS analysis whereas good adhesion between the two components has been evidenced by SEM observations. Growth of the polyester chains on the starch granules has been followed by the increase of the mean diameter of the 'encapsulated' granules as attested by laser scattering granulometry.     

Tetraf luoromethane Injected into a dc Argon Glow Discharge

Low partial pressures (10^?5 to 10^?3 Torr) of tetrafluoro-methane have been injected into a dc argon glow discharge (85 × 10^?3 Torr, 1000 V) and the discharge-induced removal rate of the CF₄ molecules from the vapor phase has been studied with a mass spectrometer as a function of the discharge current and the CF₄ concentration. The ultimate disposition of the CF₄ is believed to be in the form of polymeric deposit on the walls of the discharge vessel. The removal rate of CF₄ is proportional to the discharge current and also proportional to the concentration of CF₄in the low concentration regime. At higher partial pressures of CF₄ (～1 × 10^?3 Torr) the removal rate tends to saturate, becoming independent of the CF₄ concentration.     

稻米淀粉崩解值的近红外透射光谱法测定

以203份稻米为样品,近红外透射光谱分析仪,对样品进行光谱扫描,并用快速粘度分析仪测定稻米淀粉崩解值.采用改进的偏最小二乘法进行定标模型的建立,得到了稻米淀粉崩解值测定的近红外分析模型的定标标准偏差(SEC)、交叉检验标准误差(SECV)和定标决定系数(RSQ)分别为:10.62、10.8和0.984,内部交叉验证的经校正的工作标准差(SEP)、检验偏差(BIAS)和交叉检验相关系数(1-VR)分别为:6.139、-0.362和0.939,相关性达极显著水平.内部交又验证和外部验证结果表明近红外定量分析崩解值有很高的准确度.近红外透射光谱技术为快速准确无损测定黏滞特性指标提供了一条新途径.     

大黄种子中蛋白质、多糖和淀粉含量的测定

采用凯氏定氮法、苯酚-硫酸比色法和双波长比色法测定唐古特大黄种子、掌叶大黄种子和药用大黄种子的蛋白质、多糖和淀粉的含量.采用凯氏定氮法测定蛋白质含量,苯酚-硫酸比色法测定多糖含量,双波长比色法测定淀粉含量.唐古特大黄种子的蛋白质和多糖在三种大黄种子中含量最高,分别为21.81％、6.58％,掌叶大黄种子淀粉含量在三种大黄种子中最高,含量为32.95％.三种大黄种子中,蛋白质含量为：唐古特大黄种子＞掌叶大黄种子＞药用大黄种子;多糖含量为：唐古特大黄种子＞掌叶大黄种子＞药用大黄种子;淀粉含量为：掌叶大黄种子＞唐古特大黄种子＞药用大黄种子.大黄种子的蛋白质、多糖、淀粉含量丰富.测定方法精密度、准确度、稳定性均符合生物样品测定要求,可用于大黄种子蛋白质、多糖和淀粉含量的测定.     

Size control synthesis of starch capped-gold nanoparticles

Metallic gold nanoparticles have been synthesized by the reduction of chloroaurate anions [AuCl₄]⁻ solution with hydrazine in the aqueous starch and ethylene glycol solution at room temperature and at atmospheric pressure. The characterization of synthesized gold nanoparticles by UV–vis spectroscopy, high resolution transmission electron microscopy (HRTEM), electron diffraction analysis, X-ray diffraction (XRD), and X-rays photoelectron spectroscopy (XPS) indicate that average size of pure gold nanoparticles is 3.5 nm, they are spherical in shape and are pure metallic gold. The concentration effects of [AuCl₄]⁻ anions, starch, ethylene glycol, and hydrazine, on particle size, were investigated, and the stabilization mechanism of Au nanoparticles by starch polymer molecules was also studied by FT-IR and thermogravimetric analysis (TGA). FT-IR and TGA analysis shows that hydroxyl groups of starch are responsible of capping and stabilizing gold nanoparticles. The UV–vis spectrum of these samples shows that there is blue shift in surface plasmon resonance peak with decrease in particle size due to the quantum confinement effect, a supporting evidence of formation of gold nanoparticles and this shift remains stable even after 3 months.     

在淀粉存在下结晶紫-磷钼杂多酸光度法测定微量磷

研究了在淀粉存在下结晶紫 磷钼杂多酸光度法测磷的方法。在 0 15mol·L- 1 H2 SO4 的介质中 ,缔合物的最大吸收峰为 5 4 8nm ,其表观摩尔吸光系数为 1 98× 10 5L·cm- 1 ·mol- 1 ,室温下至少稳定 2 4h。磷在0～ 8μg·(5 0mL) - 1 范围内符合比尔定律 ,磷与结晶紫之比为 1∶5 ,方法应用于铁基试样中磷的测定。     

Critical review on alterations in physiochemical properties and molecular structure of natural polysaccharides upon ultrasonication

Natural polymers, such as polysaccharides, cellulose, and starch, have been widely used in the chemical engineering, medicine, food, and cosmetics industries, which had a great many of biological activities. Natural polysaccharides origin from algae, fungi and plants were components of human diet since antique times. Ultrasonication achieved the breakage the polysaccharides reticulum in an ordered fashion. The factors of temperature, ratio of water/material, sonication frequency, time of exposure, pH of the sonication medium influenced the polysaccharide digestion. Sonication improved the enzyme catalysis over its substrate molecule. Positive health promoting slow digestive starch and resistant starch can be prepared quite easily by the sonication process. The aim of this review is to present the current status and scope of natural polymers as well as some emerging polymers with special characteristic. The physiochemical properties and molecular structure of natural carbohydrates under ultrasonic irradiation were also discussed. Moreover, Polysaccharide based films had industrial applications is formed by ultrasonication. Polysaccharide nanoparticles obtained by sonication had efficient water holding capacity. Sonication is an advanced method to improve the food quality. Hence, this review describes the effects of ultrasonication on physical, chemical, and molecular structure of natural polysaccharides.