The effect of temperature on the observed flow-induced structure in semidilute solutions of gently solubilized starches

The effect of temperature on the unexpected shear-thickening behavior exhibited by semidilute solutions of waxy maize starch during a repeated shear-loop experiment was evaluated. Shear-thickening behavior, characterized using power law models, was observed for waxy maize starch, but not for normal maize starch at the same concentration. The shear-thickening region was observed for waxy maize starch at temperatures ranging from 25°C to 80°C and shear rates from 2–100 s^?1 during the initial part of the shear-loop experiment. For waxy maize starch, the power law exponent, n, was found to be 0.539 ± 0.017 in the shear-thinning region. For normal maize starch, the value of n was found to be equal to 0.751 ± 0.015 and only shear-thinning behavior was observed. The values of n for both waxy maize and normal maize starch were found to be temperature independent within the precision of the experimental measurements. The differences in n indicate the differences in the conformational dynamics of waxy maize and normal maize starches in solution.     

Modification of starch–poly(methyl acrylate) graft copolymers by steam jet cooking

Starch-g-poly(methyl acrylate) containing 12.3, 31.9, 51.7, and 58.3% PMA, by weight, were prepared by ceric ammonium nitrate-initiated polymerization of methyl acrylate onto granular cornstarch. The granular structures of these graft copolymers were not disrupted by steam jet cooking at 140°C. At most, only 13% of the polymer was dissolved, and this soluble fraction was comprised largely of starch. The probability of crosslinking within these graft copolymer granules was considered. Physical properties of extruded ribbons depended upon whether or not granular graft copolymers were jet cooked prior to extrusion. Although tensile strengths were not greatly affected by steam jet cooking, cooked samples showed significant increases in both percent elongation and tear resistance. The effects of jet cooking upon the properties of extruded ribbons can be explained by gelatinization of starch within the grafted starch granules. Although jet-cooked granules still remain intact, gelatinization of the starch moiety causes these granules to be less rigid, more deformable, and more easily plasticized by small amounts of water. Loss of starch crystallinity after steam jet cooking was proved by both differential scanning calorimetry and X-ray diffraction. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1021–1029, 1997     

Jet-cooked starch-oil composite in polyurethane foams

A new jet-cooked starch—oil composite has been blended with a polyester polyol and then reacted with isocyanate to give a polyurethane foam. Infrared spectroscopy and microscopy have been used to examine the resultant products. Infrared spectra have shown the products contain the urethane structures and light and electron microscopy have shown the differences in the cell wall structures and networks of the foams when compared to the control foams. Inclusion of the starch—oil composite in the formulation resulted in increased viscosity of the reaction mixture as well as a more irregular cellular structure and a rougher texture of the cured foam. Larger cells were more abundant and there was more evidence of tearing during expansion. The scanning electron photomicrographs show the open-cell structure of both the control and blended foams and their reticular network, which is more uniform in the control. This examination provides insight into the foaming process and provides information to make the necessary adjustments for acquiring the desired polymeric product. Incorporation of the starch—oil composite in polyurethane foams provides a new dimension of possibilities for enhancing their physical, functional, and environmental properties. © 1997 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

J Appl Polym Sci 64: 1355–1361, 1997     

Thermoplastic starch blends with a poly(ethylene-co-vinyl alcohol): Processability and physical properties

We investigated the effect of poly(ethylene-co-vinyl alcohol) (EVOH) concentration on the processability and physical properties of thermoplastic starch plasticized with glycerine and water. Waxy maize starch (Amioca), native corn starch (Melogel), and a treated high amylose corn starch (Hylon VII) were employed to explore the effect of starch type on blend properties. All the starches exhibited similar changes in properties with increasing EVOH content. The minimum injection pressure required for filling a standard test specimen (a measure of processability) decreased with increasing EVOH concentration and provided an indication of improved processability. Blends with high amylose corn exhibited higher injection pressures than the corresponding waxy maize or native corn starch blends. The ductility of all the thermoplastic starches was significantly increased upon the addition of EVOH. The waxy maize blends were stiffer and the high amylose corn blends exhibited higher elongation at low EVOH concentrations, but all the starch/EVOH blends exhibited similar physical properties when the EVOH concentration was ≥ 50 wt%. An investigation of physical properties of this blend series after long term aging from 10% to 90% relative humidity is in progress. Future studies include rheology, electron microscopy, and thermal analysis to more fully elucidate phase behavior in these binary blends.     

Effect of enzymatic treatment of different starch sources on the in vitro rate and extent of starch digestion

Gelatinized wheat, potato and waxy maize starches were treated enzymatically in order to increase the degree of branching of the amylopectin fraction and thereby change the starch degradation profile towards a higher proportion of slowly digestible starch (SDS). The materials were characterized by single-pulse (1)H HR-MAS NMR spectroscopy and in vitro digestion profile according to the Englyst procedure. Using various concentrations and incubation times with branching enzyme (EC 2.4.1.18) without or with additional treatment with the hydrolytic enzymes; β-amylase (EC 3.2.1.2), α-glucosidase (EC 3.2.1.20), or amyloglucosidase (EC 3.2.1.3) the proportion of α-(1-6) linkages was increased by up to a factor of 4.1, 5 and 5.8 in waxy maize, wheat and potato starches, respectively. The proportion of SDS was significantly increased when using hydrolytic enzymes after treatment with branching enzyme but it was only for waxy maize that the proportion of α-(1-6) bonds and the in vitro digestion profile was significantly correlated.     

Effect of minor addition of xanthan on cross‐linking of rice starches by dry heating with phosphate salts

Effects of xanthan on the crosslinking of normal and waxy rice starches using a mixture of phosphate salts (sodium trimetaphosphate and sodium tripolyphosphate, 99 : 1, dry solid basis) were investigated. The starch (158.4 g, dry solids) was dispersed in an aqueous solution containing xanthan and phosphate salts (1.6 and 0.6 g in 280 mL water, respectively), and the slurry was dried overnight at 45°C until the moisture content was less than 10%. The dry cake was then ground into powders and heated for 2 h at 130°C in a convection oven. The pasting viscosity, paste clarity, melting and in vitro digestion behaviors of the starches with modifying agents (xanthan and phosphate salts) were investigated. The heat treated starches displayed enhanced shear stability and reduced breakdown, as evidences of crosslinking. Xanthan (1.0% based on starch solids) enhanced the crosslinking effects in the viscosity profile. Waxy rice starch evidenced more profound viscosity changes than did normal rice starch, indicating it was more susceptible to the heat treatment. The waxy rice starch heated with the mixture of phosphate salts and xanthan exhibited a continuous increase in pasting viscosity without any breakdown. Under a DSC analysis, melting enthalpy decreased but melting temperature increased somewhat as results of the heat treatment with xanthan. In an in vitro digestion analysis, the starches treated with xanthan exhibited decreases in the maximum digestion level, and increases in the resistant starch (RS) content. Dry heating, however, increased the digestion rate and glycemic index (GI) regardless of the presence of phosphate salts or xanthan indicating that the starches were thermally degraded. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Effect of graft-copolymerization with poly(acrylamide) on rheological and thermal properties of cassava starch

Graft copolymers of different grafting levels were synthesised by the free radical initiated reaction of cassava starch with acrylamide in presence of ceric ammonium nitrate. The viscosity properties of the native granular starch and the grafted starches were determined using a Rapid visco analyzer (RVA) and rheological properties by frequency sweep test under different conditions using a rheometer. Some of the grafted starches exhibited significantly higher and some others exhibited drastically reduced peak viscosity values irrespective of the percentage grafting. All the grafted starches exhibited very good viscosity stability as evidenced from the highly reduced breakdown and higher final viscosity values in comparison to native cassava starch. Thermal analysis of the pure granular cassava starch and grafted starches was carried out using a differential scanning calorimetry (DSC) and thermogravimetry. DSC studies showed that in comparison to native starch, the grafted starches showed lower temperatures of transition. The thermal stability of cassava starch was enhanced by grafting as observed from the thermogravimetric data. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

蜡质玉米羧甲基淀粉的合成与表征

以蜡质玉米淀粉为原料,用乙醇溶剂法制备了蜡质玉米羧甲基淀粉(CMS)。考察了碱化时间、醚化反应温度、醚化反应时间、n(NaOH)/n(淀粉)、n(ClCH2COONa)/n(淀粉)对CMS粘度的影响。结果表明,在醚化反应时间2.5 h,n(NaOH)/n(淀粉)为0.4,n(ClCH2COONa)/n(淀粉)为1.2,醚化反应温度65℃,碱化时间为50 min的最佳反应条件下制得的CMS粘度为1 490 mPa.s。同时发现,随着n(ClCH2COONa)/n(淀粉)的增大,CMS粘度表现出先增大后减小再增大,最后减小的趋势,对其进行了分析。     

The distribution of lipids in the germ,endosperm, pericarp and tip cap of amylomaize,LG-11 hybrid maize and waxy maize

The quantitative distribution of 23 acyl lipid classes and unsaponifiable matter in kernels of amylomaize, LG-11 hybrid maize and waxy maize is described. LG-11 and waxy maize were normal (oil content) varieties, containing 4.9% and 5.1% lipid, respectively, while amylomaize (9.3% lipid) was a high oil variety. The distribution of kernel lipids was 76–83% in germ, 1–2% in pericarp, 1% in tip cap, 1–11% in starch, and 13–15% in aleurone plus the nonstarch fraction of the starchy endosperm. Germ contained 39–47% lipid, which was nostly triglyceride (TG), with some steryl esters (SE) and diglycerides (DG), and small amounts of glycolipids (GL) and phospholipids (PL). Aleurone lipids appeared to be TG with some free fatty acids (FFA) and SE. The other nonstarch lipids in starchy endosperm were FFA with very small amounts of SE, DG, GL and PL. The starches had a little surface lipid (FFA) and true (internal) starch lipid (FFA, lyso-PL) in quantities roughly related to amylose content (amylomaize =ca. 73% amylose, 1.0% lipid; LG-11=23% amylose, 0.7% lipid; waxy maize =<5% amylose, 0.2% lipid). Pericarp lipids (0.8–2.5%) were mainly unsaponifiable matter, the acyl lipids being TG, SE, DG and FFA. Tip cap lipids (2.5–2.9%) had more TG, GL and PL than pericarp lipids, but were otherwise similar. Pericarp lipids and endosperm nonstarch lipids appeared to have suffered extensive degradation at some time during kernel development or after harvesting, while lipids in starch, germ and tip cap were evidently unaffected. FFA and lyso-PL are regarded as normal components of maize starch (rather than degradation products) and may occur as amylose inclusion complexes.     

Effects of drying process for amorphous waxy maize starch on theophylline release from starch‐based tablets

Physical properties and theophylline‐release profiles of compressed tablets prepared with amorphous waxy maize starches dried using different methods were examined. A gelatinized waxy maize starch paste (10% solids in water) was either freeze‐dried or oven‐dried (40 or 105°C) until the moisture content reached to <5%. To form the tablets, the dried amorphous starch powders, either with or without theophylline (3 : 10, w/w), were remoistened to a water content of (17 ± 0.2)%, and compressed into tablets. The drying process applied to the amorphous starch powders affected both the compactness and swelling behavior of the tablets. Although no crystallinity was detected in all the starches tested, X‐ray diffraction patterns indicated that starch chains dried at the lower temperature (40°C) are allowed more time to re‐associate during the drying process than those dried at the higher temperature (105°C). The freeze‐dried starch powders formed tablets characterized by greater compactness and rigidity than was observed in the oven‐dried starch samples. The drug release of the tablets prepared with the starch dried at the higher temperature (105°C) occurred at a much slower rate than that of the tablets made with the starch dried at the lower temperature (40°C). The drug release characteristics of the freeze‐dried starch tablets were nearly identical to those of the tablets prepared with the starch dried at 105°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

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.     

Starch Derivatives of High Degree of Functionalization, 8. Synthesis and Flocculation Behavior of Cationic Starch Polyelectrolytes

Water soluble starch derivatives with a high degree of substitution (DS) up to 1 containing quaternary ammonium groups were prepared by reacting starch with 3‐chloro‐2‐hydroxypropyltrimethylammonium chloride (QUAB®188) in ethanol/sodium hydroxide/water or preferably with 2,3‐epoxypropyltrimethylammonium chloride (QUAB®151) in aqueous‐alkaline solution. The DS values of the samples can be controlled by adjusting the molar ratio of cationization agent to anhydroglucose unit and is only slightly dependent on the amylose content of the starting starch material. The structure of the cationic starch derivatives was confirmed by means of NMR spectroscopy. Dewatering experiments with the cationic starch derivatives were conducted on a harbor sediment suspension using a laboratory pressure filtration apparatus. The cationic starches were used alone and in combination with a high‐molar‐mass synthetic polyanion. Both dependence on the DS of the sample and influence of the amylose/amylopectin ratios of the initial native starch were observed. The highest dewatering index of 63 was found for the cationic polyelectrolyte based on the amylopectin‐rich waxy maize starch in monoflocculation. In case of dual flocculation using additionally a poly(acrylamide‐co‐acrylate) a dewatering index of even 85 was attained.     

Effect of hyperbranched poly(citric polyethylene glycol) with various polyethylene glycol chain lengths on starch plasticization and retrogradation

A series of hyperbranched poly(citric polyethylene glycol) (PCPEG) materials with varied polyethylene glycol (PEG) chain lengths as plasticizers were mixed with maize starch (MS) via cooking and film‐forming. The structure, pasting property, plasticization, aging property, moisture absorption and compatibility of plasticized starches were studied by means of Fourier transform infrared spectroscopy, X‐ray diffraction, rapid viscosity analysis, tension testing, moisture absorption measurements and scanning electron microscopy. Compared with PEG and citric acid, PCPEG was more effective in promoting starch chain movement and inhibiting the retrogradation of starch film. Also, PCPEG/MS had smaller moisture content. The longer the plasticizer chain, the better were the aging resistance and moisture resistance of starch. But with an increase of PEG chain length, mechanical properties of PCPEG/MS deteriorated and the compatibility between PCPEG and MS decreased. The hyperbranched derivative of PEG with longer chain exhibited improved plasticization and compatibility with starch. © 2019 Society of Chemical Industry     

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.     

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.     

Base-hydrolyzed starch-polyacrylonitrile (S-PAN) graft copolymer. S-PAN-1:1, PAN M.W. 794,000

Starch-polyacrylonitrile (S-PAN) graft copolymer consisting of one part starch and one part polyacrylonitrile (M. W. 794,000) was hydrolyzed with aqueous KOH at 80 and 100°C to polyelectrolytes containing carboxyl and amide functionality but void of infrared-detectable amounts of nitrile. Viscosities of potassium salts of the polyelectrolytes in water were pH dependent with peak viscosities at 8.5. These dispersions were characterized by unusually high viscosities, 15,000 to 26,500 cp at 1% concentration, and by the ability to retain significant viscosities, 300 to 950 cp, upon dilution to 0.03% concentrations. A 1% dispersion of hydrolyzed S-PAN had a viscosity of 5,000 cp in the presence of 8% KCl; however, the depressing effect of added salts on viscosity of aqueous dispersions of hydrolyzed S-PAN increases as the valence of the cation increases.     

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 °）。     

Enzymatic hydrolysis of extruded-expelled soy flour and resulting functional properties

Limited hydrolysis (4% degree of hydrolysis) of extruded-expelled soy flour protein (protein dispersibility index=21) that was poor in solubility and other functional properties was evaluated at pilot-plant scale (5 kg of flour) with two endopeptidases and one exopeptidase. Some hydrolysates were merely spray-dried whereas others were jet-cooked at 104°C for 19 s before spray-drying. Solubility, emulsification capacity and stability, foaming capacity and stability, apparent viscosity, and sensory attributes were then characterized. The type of protease used and hydrothermal cooking affected functional and sensory properties. Protein solubility modestly increased with hydrolysis and jet cooking, but emulsification capacity decreased on hydrolysis and was not restored with hydrothermal cooking. Emulsion stability improved in the endopeptidase hydrolysates, but not in the exopeptidase hydrolysates. The foaming capacities of the hydrolysates for both types of enzymes were better than for the unhydrolyzed control. Highly stable foams were obtained after hydrolyzing with exopeptidase and hydrothermal cooking. Ten percent protein hydrolysate dispersions showed large losses in consistency coefficient apparent viscosity, which increased significantly with hydrothermal cooking only for the unhydrolyzed control. Difference-from-control sensory evaluation indicated that both jet-cooked and non-jet-cooked enzyme hydrolysates were different from unhydrolyzed controls.     

Characterization of cationic starch: An efficient flocculating agent

Starch is a known carbohydrate in which, regardless of its origin, two polysaccharides are found namely amylose and amylopectin. By insertion of a cationic moiety to the backbone of starch, a modified cationic starch can be developed which can be used as flocculant. Various grades of cationic starches were developed to optimize the best performing flocculant. The base polysaccharide, starch and the best performing cationic starch i.e., Cat St3 (which have been confirmed from flocculation characteristics and intrinsic viscosity measurement) have been characterized by various characterization techniques such as determination of molecular weight, elemental analysis, FTIR spectroscopy, intrinsic viscosity measurement, thermal analysis, etc. From the characterization, it could be concluded that there was a substantial incorporation of cationic moiety onto the backbone of starch. The flocculation efficacy of these cationized starches was compared with each other and with some of the commercial flocculants available in national and international market in manganese ore suspensions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The synthesis and properties of a cation-exchange resin prepared by the pyrolysis of starch in the presence of phytic acid

A black charcoal-like material having cation exchange and adsorption properties was prepared by the controlled pyrolysis of starch in the presence of a commercial phytic acid solution. Resins with binding capacities of 0.7–5.7 meq/g of calcium were prepared by varying the phytic acid to starch ratio, the temperature, or the duration of heating of the reaction mixture. SEM photomicrographs of some of these new materials showed that they are composed of particles similar in size and shape to the starting starch granules. These resins also removed atrazine from aqueous solutions. © 1995 John Wiley & Sons, Inc.

1 This article is a US Government work and , as such, is in the public domain in the United States of America.