微波场对小麦淀粉性质的影响

研究了微波辐射前后小麦淀粉物化性质的变化。采用微波对水分含量30％的小麦淀粉进行处理。结果表明微波处理淀粉颗粒表面出现小孔,微波处理增强了对应X射线衍射峰的强度,降低了膨胀度、溶解度、析水率以及焓值,提高了糊化转变温度、转变温度范围。小麦淀粉经处理后糊化起始温度升高、黏度降低,但其黏度曲线不改变。以上数据表明在淀粉颗粒内无定形区和结晶区的直链淀粉与直链淀粉、直链淀粉与支链淀粉发生交互作用,产生了新的不同稳定性的结晶体,从而导致微波处理淀粉内部更加有序的结晶排列。     

Hydrolysis of granular starch at sub-gelatinization temperature using a mixture of amylolytic enzymes

Native granular starches (corn, cassava, mung bean, and sago) were hydrolyzed using a mixture of alpha-amylase and glucoamylase at 35 °C for 24 h. Hydrolyzed starches were analyzed for the degree of hydrolysis and for physicochemical and functional properties. Corn starch showed the highest degree of hydrolysis, as evidenced by the presence of distinct pores penetrating deep into the granules. Enzymatic erosion occurred mainly at the surface for cassava, whereas isolated porous structures were observed in hydrolyzed mung bean and sago starch. The amylose content was significantly lower in all starches except for sago starch. The powder X-ray diffraction of all starches showed no significant changes after hydrolysis, but hydrolyzed starches showed a more crystalline nature. The action of enzymes caused significant changes in some pasting properties and in the swelling/solubility of starches. Evidently, enzymes were able to hydrolyze granular starches to a variable degree at sub-gelatinization temperature, and produced a relatively high degree of conversion.     

Physicochemical properties of Venezuelan breadfruit (Artocarpus altilis) starch

Artocarpus altilis, seedless variety, is a fruit-producing plant which is cultived in Margarita Island, Venezuela, and is consumed by the inhabitants of the region. Its chemical composition and physical characteristics were determined. The chemical (AOAC and AACC methods), physicochemical, morphometric characteristics, viscoamylographic properties and digestibility in vitro of starch from Artocarpus were studied. The starch yield was 18.5 g/100 g (dw)w with a purity of 98.86%, 27.68 and 72.32% of amylose and amylopectin, respectively. Scanning electron microscopy showed irregular-rounded granules. Swelling power, water absorption and solubility values were determined and found to be higher than that of corn and amaranth starch. The amylographic study showed a gelatinization temperature at 73.3 degrees C, with high stability during heating and cooling cycles. Artocarpus starch could also be categorized in the group of mixed short chain branched/long chain branched glucan starches, this agrees with digestibility results that showed a high degree of digestibility in vitro. These results might be advantageous in medical and food use.     

酶促酯化制备松香酸淀粉酯的性质及结构表征

以松香和木薯淀粉为原料,二甲基亚砜（DMSO）为溶剂,采用酶催化酯化法在温和条件下制备了取代度0.031～0.092的松香酸淀粉酯,并对其部分理化性质进行了研究。结果表明：松香酸淀粉酯的性能与其取代度密切相关。随着取代度的增大,酯化淀粉产物的可溶指数和溶胀度降低,相对黏度和特性黏度增强,分子链也随取代度的增大而增加。通过对淀粉-碘络合物的紫外光谱分析,发现随着取代度的增大,酯化产物的最大紫外吸收波长向长波长方向移动,且蓝值减小。红外光谱（FT-IR）、核磁氢谱（¹H NMR）、差示热扫描（DSC）、热重差（TGA）和扫描电镜（SEM）对不同取代度的松香酸淀粉酯表征分析的结果表明：酯化产物在1727 cm^-1处产生C O的特性吸收峰,糊化温度及热稳定性相对预处理淀粉有所降低,淀粉颗粒的结晶度下降。     

Study of the Plasticizer Effect and Characterization on Diverse Pseudo-Thermoplastic Starch Biodegradable Films

Recently, pseudo-thermoplastic starch (PTS) has been developed to replace industrial plastics because of its advantage in biodegradability. In this study, potato, corn, and wheat starches, which have been modified into PTS biodegradable films by glycerol plasticization, were investigated. For the evaluation of the suitable compositions on PTS, we focus on analysis of the plasticizer effect and characterization. As the results show that the strength and modulus of pseudo-thermoplastic potato starch (PTP) film were respectively, 12.7 and 59.6 MPa, with lower gelatinization temperature (60°C), and the thermal processibility was better than other starches. It is beneficial for the production and application of biodegradable materials.     

Extraction and Characterization of Starch from Oak Acorn,Sorghum, and Potato and Adsorption Application for Removal of Maxilon Red GRL from Wastewater

Pure starch has been isolated from different samples: oak acorn, sorghum, and potato using alkali steep and wet-milling procedure. The structure of the extracted starches was analyzed using Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction. Their physicochemical properties (water content, ash content, pH, amylose content, swelling power, and water solubility index) were determined. The FT-IR spectra of isolated native starches have shown the main bands characterizing the starch. For sorghum starch (SS) and oak acorn starch (OAS), X-ray diffractograms exhibited an A-type diffraction pattern, while potato starch (PS) displayed typical B-type pattern. Compared to sorghum and oak acorn, potato starch has shown the highest level of both swelling power and water solubility index.

To estimate the color removal quality of the extracted starches, a sorption of a dye named maxilon red GRL has been carried onto them.

The results of equilibrium isotherms in batch adsorption process were analyzed according to the Langmuir and Freundlich model. The characteristic parameters were determined for each model. Furthermore, the effect of initial pH and ionic strength on adsorption capacity was considered, and regeneration studies were carried out.     

Characterisation of Dioscorea bulbifera native starch

A non conventional source of starch, bulbs of Dioscorea bulbifera, was evaluated. Giving a yield of 28.48 g/100 g on dry weight, chemical composition, physical, physico-chemical and morphological characteristics were assessed, as well as its rheological properties. Chemical analysis showed a amylose content of 29.37%. Micrographies showed that most of the starch granules were of irregular shape, similar to a pyramid with rounded vertices, and a smaller number were elongated with smooth surface. Dioscorea starch showed a gelatinization temperature of 70.8 degrees C and maximum viscosity at 88.6 degrees C of 435 Brabender units (BU). It presented a relatively stable consistency to the cooking process and a low tendency to retrogradation; which suggest the starch possible use in food products that need a fast viscosity and a gel with a stable consistency.     

Optimization of Drum Drying Parameters for Low Amylose Rice (KDML105) Starch and Flour

An attempt was made to study and model the effects of drum drying process variables on the physico-chemical properties of low amylose rice (KDML105) flour and starch. Drum surface temperature, holding time and solid content of the slurry were varied at three levels: 115-135°C, 14-84 s and 20-40%, w/w, respectively. The dependent variables were moisture content (MC), degree of gelatinization (DG), water absorption index (WAI), water solubility index (WSI) and pasting property. High solid content led to a decrease in DG, WAI and initial peak viscosity (IPV) and increase in WSI of dried samples. Longer holding time resulted in increased DG while surface temperature had no significant effect on all characteristics. Predictive correlations were developed using stepwise multiple linear regression to predict MC, DG, WAI, WSI, and IPV of dried products from drum drying variables.     

Change of mechanical properties related to starch gelatinization and moisture content of rice kernel during fluidized bed drying

Rice fissuring during the drying process is a major problem affecting rice quality. To alleviate this critical issue, it is necessary to understand the change of mechanical properties and the drying kinetics of paddy during drying. The objective of this work is therefore to study the drying characteristics and changes of mechanical properties, i.e., breaking force (F), ultimate tensile strength (UTS), and apparent modulus of elasticity (AMOE) during fluidized bed drying. Suphanburi 1 paddy variety with three initial moisture contents (Mi) of 29.5, 30.2, and 42.8% dry basis was used as the raw material, which was dried at drying air temperatures (Ta) of 110, 130, and 150?°C. A three-point bending method was used for testing the mechanical properties with a texture analyzer. The experimental results showed that the breaking force and the ultimate tensile strength of paddy during drying were more strengthened with higher drying temperatures and higher initial moisture content while its apparent modulus of elasticity was changed only with the moisture content. However, both operating parameters positively affected the apparent modulus of elasticity when evaluated at a 16% dry basis. The maximum changes in F, UTS, and AMOE concerning the initial moisture content were 25.1, 25.2, and 19.5%, respectively. Besides, the maximum changes in F, UTS, and AMOE concerning drying temperatures during drying were 14.2, 14.3, and 13.5%, respectively. The improvement of the mechanical properties could be attributed to the starch gelatinization of which the degree was higher in cases of higher initial moisture content and higher drying temperatures. The empirical models of ultimate tensile strength and apparent modulus of elasticity were developed and related to intermediate moisture content and the degree of starch gelatinization.     

Starch Consolidation Casting of Cordierite Precursor Mixtures—Rheological Behavior and Green Body Properties

The rheology of suspensions and mechanical properties of green bodies with cordierite composition (raw materials 37 wt% kaolin, 41 wt% talc, 22 wt% alumina, resulting in 46.6 wt% SiO₂, 38.1 wt% Al₂O₃, 13.6 wt% MgO) and two types of starch (corn or potato) are investigated. Rotational viscometry of suspensions with solids loading 50, 60, and 70 wt% without starch showed that all tend to be shear‐thinning with a small degree of thixotropy. Suspensions with a total solids loading of 60 wt% with 25 wt% replaced by starch exhibited higher viscosity and thixotropy, but the viscometric behavior is almost identical for the two starch types (apparent viscosities 130–50 mPa ·s). Oscillatory rheometry shows that for suspensions with potato starch the onset temperature for gelatinization is 61°C–63°C, that is, lower than for corn starch (72°C–73°C). Maximum storage moduli and phase shift values after gelatinization are similar for both systems. The mechanical properties of green disks, measured via diametral compression tests, reveal clear differences between materials prepared with corn and potato starch, with the latter showing higher elastic modulus, higher strength, and higher deformation at fracture, obviously because of incompletely gelatinized starch granules in the green bodies prepared with corn starch .     

Preparation and properties of biodegradable thermoplastic starch/poly(hydroxy butyrate) blends

The vital differences using three types of thermoplastic starches (TPS), including potato starch, corn starch, and soluble potato starch, with two different gelatinization degrees to blend with poly(hydroxy butyrate) (PHB) are thoroughly discussed in this study. For blends containing a certain amount of PHB, thermal stability remains in a certain degree. In all cases of this study, mechanical properties of TPS blended with PHB confer higher performance than those of pristine TPS. In particular, a significant increase on tensile strength and tear strength is observed for TPS (potato starch) blended with PHB at low gelatinization degree. A suitable degree of gelatinization of starch is critical to achieve optimum performance. The investigation on the morphological observation partly features the supporting evidence of the above findings. The assessment of biodegradability indicates that the values of water absorption and weight loss increase with increasing treatment period and glycerol content, but decrease with increasing amount of PHB content. Among three types of starches investigated, the TPS (soluble starch)/PHB blend gives the highest level of water absorption and weight loss. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2371–2379, 2006     

Optimization of Drum Drying Parameters for Low Amylose Rice (KDML105) Starch and Flour

Abstract

An attempt was made to study and model the effects of drum drying process variables on the physico–chemical properties of low amylose rice (KDML105) flour and starch. Drum surface temperature, holding time and solid content of the slurry were varied at three levels: 115–135°C, 14–84 s and 20–40%, w/w, respectively. The dependent variables were moisture content (MC), degree of gelatinization (DG), water absorption index (WAI), water solubility index (WSI) and pasting property. High solid content led to a decrease in DG, WAI and initial peak viscosity (IPV) and increase in WSI of dried samples. Longer holding time resulted in increased DG while surface temperature had no significant effect on all characteristics. Predictive correlations were developed using stepwise multiple linear regression to predict MC, DG, WAI, WSI, and IPV of dried products from drum drying variables.     

Influence of the glycerol content and temperature on the rheology of native and acetylated starches during and after gelatinization

Native potato starch was acetylated and characterized. The influence of this chemical modification on different properties of the starch was studied. The characterization included the molecular weight, thermal properties, crystallinity, amylose content, swelling behavior, and pasting and rheological properties. The chemical modification induced small changes in the crystallinity of the starch and a reduction in the gelatinization heat and in the range of temperatures at which it took place. The amylose content was determined for acetylated and native potato starches. The swelling of native granules was higher than the swelling of acetylated potato starch. Regarding pasting behavior, the native and acetylated starches responded in similar ways to changes in the temperature and glycerol content. Finally, the acetylated starch was less pseudoplastic than the native starch. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Alcoholic-alkaline treatment of sago starch and its effect on physicochemical properties

Sago starch (Metroxylon sagu) was subjected to an alcoholic-alkaline treatment using varied amounts of sodium hydroxide (NaOH) and a constant amount of ethanol at 35 °C. The cold water-solubility (CWS) of all the sago starches increased with an increase in the concentration of NaOH. For samples with high CWS, the Maltese-cross effect was absent when viewed under a light microscope. These granules were also larger than the native starches and had an indented appearance. The X-ray diffraction pattern changed from a C to a V for starches with high CWS. The amylose content of the treated sago starches increased significantly, whereas the intrinsic viscosity and peak viscosity values for treated starches were lower than the native starches. The gelatinization enthalpy decreased and was not detectable for sago starch with high CWS. It was evident that the alcoholic-alkaline treatment was effective for the production of granular cold water-soluble sago starches.     

不同直链含量热塑性淀粉的制备及性能研究

利用转矩流变仪,以丙三醇为增塑剂对不同来源的淀粉进行改性制备热塑性淀粉（TPS）。采用X射线衍射仪（XRD）、热重分析仪（TG）、水接触角测量仪、傅里叶变换红外光谱仪（FTIR）和扫描电子显微镜（SEM）等对获得的热塑性淀粉进行了表征。结果表明,4种热塑性淀粉均含有颗粒状和颗粒状碎片,并且在热塑性木薯淀粉中所含比例更高;淀粉在增塑过程中达到稳态的扭矩依次为木薯淀粉（23 N·m）>玉米淀粉（21 N·m）>马铃薯淀粉（17.8 N·m）>蜡质玉米淀粉（15.2 N·m）,这与不同种类来源淀粉的直链淀粉比例差异直接相关;不同类型的淀粉与增塑剂形成氢键的能力存在差异,蜡质玉米淀粉的能力最强;4种热塑性淀粉的亲水性依次为热塑性木薯淀粉（75.9 °）>热塑性玉米淀粉（69.2 °）>热塑性马铃薯淀粉（67.9 °）>蜡质玉米淀粉（64.9 °）。     

NMR and X-Ray Studies of Starches Derived from Tropical Fruit Seed Gelatinization Process

Gelatinization of the starch obtained from fruit seed such as mango and cumbaru was investigated applying an analytic methodology developed in the polymer nuclear magnetic resonance (NMR) laboratory at IMA/UFRJ, employing high resolution nuclear magnetic resonance spectroscopy in the solid state for hydrogen nucleus, using ¹H HR-MAS pulse sequence. The results showed that NMR can be used instead of some techniques normally applied to study the gelatinization process, because ¹H HR-MAS and relaxation time allow the evaluation of this process at the molecular level. NMR was also able to indicate the best gelatinization conditions. To start this study the glass transition (Tg) determination was a first step, because the Tg of seed starches are different than the Tg of starches derived from cereal, for example. The ¹H HR-MAS NMR showed some useful information on the fruit seed starches gelatinization process. X-ray measurements were also used to support the data obtained from NMR technique. It was verified, from X-ray, that mango starch exhibits crystallinity in the A form and cumbaru showed a predominant amorphous phase. The use of ¹H HR-MAS was shown to be a new, powerful method to follow the gelatinization process, because this process can be understood at the molecular level.     

The characterization of granule structural changes in acid-thinning starches by new methods and its effect on other properties

Acid-thinned starches (ATSs) have been prepared directly from hydrochloric acid-modified corn starch. The fracture mechanism of starch granule was investigated using scanning electron microscopy combined with laser particle size analysis. And the extent of ATSs chain was also first characterized using X-ray photoelectron spectroscopy. The properties of ATS were tested by X-ray diffraction, differential scanning calorimetry, thermo gravimetric analysis, and rotational viscometry. Native starch and ATSs exhibit different structures and properties. Amorphous regions of corn starch, located in the interior of the starch granule, are preferentially hydrolyzed and can lead to starch particle fracture. The relative C=O content in the ATSs are increased, indicating that the acid thinning makes the starch molecules shorter, and the fracture extent of the starch molecular chains was 240.86 and 608.97%, respectively. Acid thinning does not change the starch crystal pattern or its basic composition, but it does increase the degree of crystallinity. Compared to the native corn starch, ATSs has a higher gelatinization temperature and a lower enthalpy of gelatinization. The acid thinning treatment drastically reduces the hot paste viscosity of the starch.     

Eco-friendly denture adhesives (EFDAs) filled with different types of natural starches: mechanical and biological performance evaluation

Abstract

This research focuses on the development of eco-friendly denture adhesives (EFDAs) by studying the effects of the addition of different types of native and modified natural starches as fillers in denture adhesive properties for dental applications. The properties of EFDAs filled with single and hybrid starches in comparison with a selected commercial denture adhesive were investigated. The investigated single starches were corn, tapioca and sago while the hybrid starches used were corn/tapioca (CT), corn/sago (CS) and tapioca/sago (TS), all with ratio of 1:1. The EFDAs were prepared with 5, 10 and 15 percent (wt. %) loading of starch filler. The starches were chemically and physically modified via oxidation and gelatinization techniques. The mechanical characterization performed were tensile bonding strength (TBS), adhesiveness and hardness, as well as cytotoxicity test by using an MTT assay for biological analysis. Mechanical analysis indicated that produced EFDAs have higher tensile bond strength, adhesiveness and hardness as compared to the commercial denture adhesive. The increment was associated with the addition of hybrid starches and an optimum filler loading at 10%. The EFDAs were also non-toxic to the dental pulp stem cells (DPSC) up to 48?h. EFDA has good potential to be used as a natural based denture adhesive as it contains natural materials namely starch which enhances its properties. The properties were suitable for better denture bonding, retention and showed good interaction with the biological environment.     

Physicochemical changes in starch during corn alkaline-cooking in varieties with different kernel hardness

Changes in starch characteristics caused by alkaline-cooking in two corn genotypes (hard and soft) were studied in the present work. Color, pH, pasting properties (Brabender viscoamylograph), water sorption, solubility, swelling power and thermal analysis (Differential scanning calorimetry) were determined in starches previously extracted, from raw and alkaline-cooked hard and soft corns. A reduction in maximum viscosity peak, temperature at the endothermic peak and swelling power at 90 degrees C, and an increase in solubility was observed in starches obtained from both hard and soft corn after alkaline-cooking. Starch from hard corn showed an increment in initial pasting temperature after alkaline-cooking. Alkaline-cooking induced higher modifications in hard than in soft corn starch, probably as a result of its endosperm type and grain hardness, although optimum cooking times were used for each corn genotype.     

Comparative study of maize cultivars 30 days after pollination (30 DAP): characterization of starch

Characterization of starch was comparatively studied in five maize cultivars, i.e., Maya Normal, Nutrimaiz, two hybrids (L90 x L78, L90 x L41) and Supersweet (SRR "Duro"), 30 days after pollination (30 DAP). Amylose content was found to be higher in the Maya Normal starch (31.3%) and lower (23 to 27%) in the genetically-modified cultivars. The absolute density of the isolated starches did not show significant differences among cultivars. Solubility and swelling studies suggested the presence of more homogenous forces maintaining the granular matrix on the starch from Maya Normal in relation to the other maize cultivars. The starch from the genetically-modified cultivars had a reduced solubility in dimethylsulfoxide and lower values for the gelatinization temperature range, in comparison to the Maya Normal. Information from the Brabender amylogram indicated greater resistance of the gelatinized maize starches to granule breakdown by mechanical stirring, in the new genotypes, resembling those starches modified by cross-linking.