非对称场流分离系统的构建及其在淀粉颗粒粒径表征中的应用

淀粉颗粒粒径与分子尺寸分别在1~100 μm和20~250 nm之间,是影响淀粉功能特性的重要因素之一。非对称场流分离(AF4)是一种基于样品与外力场相互作用机制的分离技术,已应用于表征淀粉分子尺寸分布。商品化的AF4系统的粒径检测范围为1 nm~10 μm,对于淀粉颗粒粒径表征具有一定的局限性。该文研制了AF4分离系统;考察了其在微米尺度下对红薯、莲子和大米淀粉颗粒粒径表征的性能;采用微米尺寸的聚苯乙烯乳化球(PS)标准样品验证了构建的AF4系统的分离性能。实验结果显示,构建的AF4系统对PS混合样品(粒径2、6、12、20 μm)实现了基线分离,同商品化AF4相比提高了检测上线,具有分离表征淀粉颗粒的潜力。此外,该文研究了载液组成对淀粉颗粒分离表征的影响;通过光学显微镜验证了构建的AF4系统在微米尺度上对淀粉颗粒粒径分布的表征能力。最后,采用商品化的AF4系统串联多角度激光光散射检测器和示差折光检测器对3种淀粉分子进行了分离表征,考察了淀粉的溶解温度对其表征结果的影响。在摩尔质量10 ⁶~10⁸ g/mol范围内,红薯和莲子淀粉的回转半径和水合半径的比值(R_g/R_h)在0.9~1.1之间,大米淀粉的R_g/R_h在1.2~1.4之间。实验结果证明构建的AF4系统是一种快速、准确的淀粉颗粒粒径表征方法,与商品化的AF4系统结合可为研究淀粉尺寸分布与其功能性质之间的关系提供技术支持。     

Processing and characterization of waxy maize starch films plasticized by sorbitol and reinforced with starch nanocrystals

Nanocomposites films have been processed from a filler and a matrix having the same nature, i.e. waxy maize starch. The filler consists of nanoplatelet-like starch particles obtained as an aqueous suspension by acid hydrolysis of starch granules and the matrix was prepared by plasticization and disruption of starch granules with water and sorbitol. Nanocomposite films were obtained by casting and evaporating the mixture of the aqueous suspension of starch nanocrystals with the gelatinized starch. The resulting films were conditioned before testing and the effect of accelerated ageing in moist atmosphere was investigated. The thermal properties of the nanocomposite films were determined from DSC measurements and the mechanical characterization was performed in both the linear and nonlinear range.     

Starch Granule Size and Morphology of Arabidopsis thaliana Starch-Related Mutants Analyzed during Diurnal Rhythm and Development

Transitory starch plays a central role in the life cycle of plants. Many aspects of this important metabolism remain unknown; however, starch granules provide insight into this persistent metabolic process. Therefore, monitoring alterations in starch granules with high temporal resolution provides one significant avenue to improve understanding. Here, a previously established method that combines LCSM and safranin-O staining for in vivo imaging of transitory starch granules in leaves of Arabidopsis thaliana was employed to demonstrate, for the first time, the alterations in starch granule size and morphology that occur both throughout the day and during leaf aging. Several starch-related mutants were included, which revealed differences among the generated granules. In ptst2 and sex1-8, the starch granules in old leaves were much larger than those in young leaves; however, the typical flattened discoid morphology was maintained. In ss4 and dpe2/phs1/ss4, the morphology of starch granules in young leaves was altered, with a more rounded shape observed. With leaf development, the starch granules became spherical exclusively in dpe2/phs1/ss4. Thus, the presented data provide new insights to contribute to the understanding of starch granule morphogenesis.     

机械活化木薯淀粉氧化产物的结构表征

采用搅拌球磨机对木薯淀粉进行机械活化,以活化60min的木薯淀粉为原料,CuSO4为催化剂,H2O2为氧化剂干法制备氧化淀粉。利用红外光谱、扫描电子显微镜、X-射线衍射等手段对产物的结构进行表征分析,并与原淀粉的氧化产物进行比较。结果表明,机械活化对木薯淀粉的氧化反应有显著的影响。原木薯淀粉的氧化反应主要发生在淀粉颗粒的表面及无定形区,部分发生在结晶区,产物是无定形及结晶状态的结构;活化淀粉的氧化反应在淀粉团粒表面及内部均匀进行,产物是无定形的聚集状态结构。并就机械活化对淀粉氧化的强化机理进行了探讨。     

Solid-state NMR study of biodegradable starch/polycaprolactone blends

Abundant literature exists on starch or modified starch blended with biodegradable polyesters to achieve good performance with cheap compost plastics. The level of miscibility in these blends is one of the most relevant parameters. In the present study, solid-state ¹H and ¹³C NMR spectra, as well as carbon spin-lattice relaxation times T₁(C) and proton spin-lattice relaxation times T₁(H) and proton spin-lattice relaxation times in the rotating frame T_1ρ(H) of biodegradable starch (or starch formate)/polycaprolactone (PCL) (or polyester (PE) oligomers) blends and samples of the neat components were measured. From the T_1ρ(H) and T₁(H) relaxation times it follows that blends starch/PCL, starch/PE-oligomers and starch formate/PE-oligomers are phase separated even on the scale of 20-110 nm. On the contrary starch formate/PCL blend is phase separated on the scale 2.5-12 nm but homogeneously mixed on the scale 20-90 nm. Moreover, shorter T₁(C) and especially T_1ρ(H) values found for the starch or starch formate component in all these blends in comparison with neat samples show that molecular mobility of starch and starch formate segments is affected by blending. This indicates some miscibility also in phase separated blends which can happen in amorphous channels of starch.     

Crystalline starch based nanoparticles

Starch is an abundant, natural, renewable, and biodegradable polymer produced by many plants as a source of stored energy. Because of the multiscale structure of starch granules consisting of alternating crystalline and amorphous concentric layers, the controlled acid hydrolysis treatment of starch disrupts this organization and releases crystalline platelet-like particles with nanoscale dimensions. This paper intends to provide a comprehensive overview of their preparation, characterization, properties, and applications.     

Thermal stability and degradation of starch derivatives

Thermal behaviour of different starch derivatives, i.e. starch esters and ethers having degree of substitution (DS) in the range of 0.02–0.18 were studied. Potato, maize and wheat starches were used. Measurements were carried out by coupled thermal analysis/ mass spectrometry method (STA-MS) in air atmosphere. The major DTG peak during the investigation for starch derivatives is observed below 300°C. The mass loss up to a temperature of 300°C is about 50%. The most abundant ions found areH₂O⁺ and CO₂ ⁺. For the studied starch derivatives with a low degree of substitution (DS<0.18) no correlation was found between thermal stability and the level of substitution regardless of the nature of substitution.     

Ethanolamine as a novel plasticiser for thermoplastic starch

Ethanolamine plasticised thermoplastic starch (ETPS) was prepared using a novel plasticiser ethanolamine. SEM images show that the native starch granules were destroyed, and the ethanolamine made them come into a uniform continuous phase. FTIR spectroscopy showed that the hydrogen bonds between the ethanolamine and starch molecules weakened the strong effect of starch intermolecular and intramolecular hydrogen bonds. The ETPS successfully restrains the re-crystallization of traditional thermoplastic starch plasticised by glycerol (GTPS), which was proved by XRD. The mechanical properties of ETPS, such as Young's modulus and breaking energy and the water absorption were improved. The glass-transition temperature (T_g) and thermal stability were also studied by DSC and TGA.     

Development of nanostructure in resistant starch type III during thermal treatments and cycling

The effect of recrystallization temperature on the lamellar structure of RSIII samples was studied using XRD and SAXS. The polymorph type could be manipulated in a controlled manner, independently of the plant source. In RSIII from corn starch and from high-amylose corn starch, retrogradation at a low temperature led to the formation of polymorph B with lamellas arranged in long-range periodicity, whereas retrogradation at a high temperature led to the formation of polymorphs A and V with no defined periodicity. The retrogradation temperature of wheat starch did not have a major effect on its nanostructure. For both polymorphs, the enzymatic degradation decreased as the degree of order within the crystal increased.     

Thermal transitions of cassava starch at intermediate water contents

Order-disorder transitions were investigated in native cassava starch at intermediate moisture contents (35 to 60% wt. water), using Differential Scanning Calorimetry (DSC) and dynamic Wide Angle X-ray Diffractometry (WAXS) with a synchrotron radiation source.The gelatinization of granules occurs as a cooperative process, due to constraints induced in crystallites by the amorphous areas. Variations of water content (water volume fraction from 0.28 to 0.86) and heating rate (0.2–10C min^–1) allowed access to equilibrium melting conditions. Cassava starch exhibits a higher melting temperature of the undiluted starch (T _m ^o ) and an equivalent melting enthalpy of the repeating glucosyl unit (H _u), compared to other A-type starches. At intermediate water content (45% wt. water), a two-stage melting process is evidenced, with different kinetic rates below and above 75 C.We wish to thank F. Lavigne (URA, CNRS 1218, Chatenay Malabry) for valuable help with this work and C. Bourgaux from L.U.R.E. for helping us with dynamic X-ray diffraction experiments. The present study was supported by a grant from the European Communities (STD3-CT92-0110).     

Structural and mechanical properties of edible films from composite mixtures of starch,dextrin and different types of chemically modified starch

Abstract

Recent regulations restricting the use of one-use-plastics open the possibility to develop starch-based edible packaging material. The objective of this work was to determine the effect of three different modified starches on starch and dextrin composite edible films by a mixture design approach on edible films’ mechanical properties. The amylose content of chemically modified starches influenced their swelling capacities, where higher amylose content was inversely related to water-power uptake and directly related to film thickness. CMS3 Nifrastarch-TS edible films, with higher amylose content, presented higher puncture force and tensile strength, but lower puncture deformation and elongation, related to a less smooth surface, according to atomic force micrographs. The use of CMS1 Gelamil-100, with lower amylose content, decreased stiffness but increased films’ stretching, presenting higher surface smoothness film topography. The use of commercial chemical modified starches in combination with starch and dextrin will allow to control of edible film thickness and hence, mechanical properties, depending on food covering necessities.     

Preparation ofwheat resistant starch

A suitable thermal treatment of gels of various starch varieties was assessed to achieve the formation of resistant starch (i.e. amylose crystals). On the basis of DSC data, the yield of amylose crystals and their thermal stability did not seem correlated with the amylose content of the starch. This last parameter may not therefore be referred to as the only factor that defines a resistant starch promising starch variety.     

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.     

Study on the morphology, crystalline structure and thermal properties of yellow ginger starch acetates with different degrees of substitution

Yellow ginger starch acetates with different degrees of substitution (DS) were prepared by reacting native starch with glacial acetic acid/acetic anhydride using sulfuric acid as catalyst. X-ray diffraction (XRD) of acetylated starch revealed that the crystal structure of native starch was disappeared and new crystalline regions were formed. Their formation was confirmed by the presence of the carbonyl signal around 1750 cm⁻¹, as well as the reduced hydroxyl groups, in the Fourier transform infrared spectroscopy (FT-IR). The scanning electron microscopy (SEM) suggested most of the starch granules disintegrated with many visible fragments along with the increasing DS. The thermal behavior of the native starch and starch acetate were investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA), it was observed that the thermal stability of acetylated starch depends on the degree of substitution. Thermal stability of high DS acetylated starch is much better than that of the original starch when DS reached to 2.67.     

Transitional properties of starch colloid with particle size reduction from micro- to nanometer

High-pressure homogenization was used to disperse starch particles in water and reduce the size from micro- to nanometer. The resultant starch colloids were characterized by particle morphology, mean size, size distribution, and zeta potential. Starch slurries were transformed from a mixture containing sediment, dispersion, and sol, to gel as a result of reduction of the particle size from 3–6 μm to 10–20 nm under a pressure of 207 MPa. Furthermore, this process led to the transition of fluid properties without affecting the crystal structure and thermal stability of starch granules. Viscosity of the colloids increased with an increased number of homogenization passes, accompanied by a decreased particle size, narrower particle size distribution (PSD), and an increased absolute zeta potential, indicating the formation of a suspension or stable gel composed of nanoparticles. Lognormal and two other mathematical functions were established to describe the PSDs and their relationship to the homogenization passes. Hence, an environmentally friendly means of producing starch-based nanoparticles or nanogels with high yields, and predictable size and viscosity properties was presented.     

Waxy Maize Starch Nanocrystals as Filler in Natural Rubber

Starch nanocrystals obtained from acid hydrolysis of waxy maize starch granules consist in crystalline nanoplatelets about 6–8 nm thick with a length of 20–40 nm and a width of 15–30 nm. New nanocomposite materials, i.e. natural rubber (NR) filled with waxy maize starch nanocrystals were processed by casting. Dynamic mechanical analysis has shown that starch nanocrystals were a good reinforcing agent for NR at temperatures higher than the glass transition temperature of NR. Tensile tests have shown that until a weight fraction of 20 wt%, this new filler presented the advantage to reinforce natural rubber without decreasing significantly the strain at break of the material. These properties may be due to both the morphological nature of starch nanocrystals, and the formation of a percolating starch nanocrystals network within the NR matrix, resulting from hydrogen bonding forces between starch aggregates.     

Lyocell blend fibers with cationic starch: potential and properties

The regeneration of cellulose from solution state offers opportunities for blending with a secondary polymer. Cellulose/cationic starch blends were spun into fibers from -methylmorpholine- oxide solution, and the fibers were characterized by moisture absorption, dye absorption, and enzymatic hydrolysis. Cellulose/starch-blend fibers with up to 30% starch content were found to retain up to three times as much water, take up to five times as much dye, and be degradable much faster by cellulase hydrolysis compared with control lyocell fiber. ID addition to starch content, the fiber's performance depended on the degree of substitution of the starch by cationic substituents.     

A blood substitute from hydroxyethyl starch and hemoglobin

One method to increase the retention time of hemoglobin (Hgb) is to react it with a hydroxyethyl starch (HES) molecule. To examine this hypothesis, polymer-bound hemoglobin compounds were synthesized by the dialdehyde route. The electrophoretic mobility patterns indicate complete binding of the Hgb. Preliminary exchange-transfusion experiments in rates showed that they could survive for at least 10 h at Hct<10% when transfused with 6% HES-Hgb solutions. The retention time of the Hgb in the urine was increased to 12 h with these new polymers.     

Fabrication of starch blend films with different matrices and their mechanical properties

The objective of the study was to determine the effects of molecular sizes of amylose (AM) and starch granules on the mechanical properties of thermoplastic starch (TPS) blend films. Leached amylose solution from cassava (CS_ AM) and mung bean (MB_AM), and two forms of amylopectin (AP) (granular; g and non-granular; ng) of waxy cassava (WxCS) starch were used. Four types of film matrices were fabricated and all TPS blend films contained same amount of AM and glycerol. Results displayed that molecular weight profiles of starch films and presence of granule remnants significantly controlled the film matrix formation, types of crystal formation, and percent of relative crystallinity (%RC) (p < 0.05). Tensile property of TPS films was controlled by %RC and presence of granule remnants. Percent elongation at break (%E_b) of TPS films increased when the films had a large range of molecular weight distribution (from 5.5 × 10⁷ g/mol to 0.4 × 10⁵ g/mol) and contained a high weight fraction (~58%) of starch molecules with M_w~0.4 × 10⁵ g/mol.     

Isothermal microcalorimetric studies on starch retrogradation

In the present study, isothermal microcalorimetry was introduced as a tool to investigate properties of starch retrogradation during the first 24 h. The study was made on purified amylose and amylopectin from corn, as well as on native starches, such as wheat, potato, maize, waxy maize and amylomaize, differing in their amylose content. The results were obtained in the form ofP-t traces (thermal powervs. time), and integration of these traces gave a net exothermic enthalpy of reaction, caused by the crystallization of amylose and amylopectin. TheP-t traces reflected the quantities of amylose and amylopectin in the starch studied. Depending on the amylose content and the botanical source of the starch, the rate of crystallization of amylose was high and predominated over that of amylopectin during the first 5–10 h. The contribution from amylose crystallization to the measured exothermic enthalpy was very substantial during this period. After 10 h, amylose crystallized at a lower constant rate. During the first 24 h, amylopectin crystallized at a low steady rate. The exothermic enthalpies obtained by the isothermal microcalorimetric investigations during the first 24 h of retrogradation were generally low in relation to the endothermic melting enthalpies observed by differential scanning calorimetry (DSC) measurements after 24 h of storage. The discrepancies in enthalpy values between the two methods are discussed in relation to phase separation and the endothermic effects owing to the decrease in polymer-water interactions when polymer-rich regions in the starch gel separate. Besides the exothermic enthalpies obtained, theP-t traces also made it possible to study the initial gelation properties of amylose from different botanical sources. The present study further demonstrated that isothermal microcalorimetry can provide a possible way to investigate the antistaling effect of certain polar lipids, such as sodium dodecylsulphate (SDS) and 1-monolauroyl-rac-glycerol (GML), when added to starches of different botanical origin. The net exothermic heat of reaction for starch retrogradation during the first 24 h was decreased when GML or SDS was added to the starch gels. The recordedP-t traces also showed how the effect of the added lipid influenced different periods during the first 24 h of starch retrogradation, and that the effect depended mainly on the amylose content, the botanical source of the starch, and the type of lipid used. When GML or SDS was added to waxy maize, the isothermal microcalorimetric studies clearly indicated some interaction between amylopectin and the polar lipids. These results concerning the action of anti-staling agents are further discussed in relation to the helical inclusion complexes formed between amylose-polar lipid and amylopectin-polar lipid.The authors thank Eva Qvarnström at the Dept. of Thermochemistry and Eva Tjerneld at the Dept. of Food Technology for valuable practical assistance. Financial support was obtained from the Swedish Council for Forestry and Agricultural Research (SJFR) and the Swedish Farmer's Foundation for Agricultural Research (Stiftelsen Lantbruksforskning).