Linfeng Wang

Physicochemical properties of common and waxy corn starches oxidized by different levels of sodium hypochlorite

Abstract Structure and physicochemical properties of oxidized common and waxy corn starches by different levels of sodium hypochlorite (0.25–3.0% active chlorine based on dry starch weight) were studied. The oxidized common corn starch generally had a higher carboxyl content but a similar carbonyl content compared with the oxidized waxy corn starch. The introduction of carboxyl and carbonyl groups promoted starch hydration and swelling. The gelatinization temperature of the oxidized starches increased but the enthalpy remained unchanged. Oxidation at low concentrations of chlorine (≤1.0%) produced starch with significantly higher peak and final viscosities and less breakdown as measured by Micro Viscoamylography. The carboxyl groups formed hemiacetal crosslinks that strengthened the starch integrity. However, as more amylose and amylopectin were degraded at higher oxidation levels, the depolymerization of starch molecules overrode the effects of crosslinking. Both amylose and amylopectin were oxidized and degraded during oxidation but amylose was more susceptible to oxidation.

Structures and Physicochemical Properties of Acid-Thinned Corn, Potato and Rice Starches

The structures and physicochemical properties of acid-thinned corn, potato, and rice starches were investigated. Corn, potato, and rice starches were hydrolyzed with 0.14 N hydrochloric acid at 50 °C until reaching a target pasting peak of 200—300 Brabender Units (BU) at 10% solids in the Brabender Visco Amylograph. After acid modification the amylose content decreased slightly and all starches retained their native crystallinity pattern. Acid primarily attacked the amorphous regions within the starch granule and both amylose and amylopectin were hydrolyzed simultaneously by acid. Acid modification decreased the longer chain fraction and increased the shorter chain fraction of corn and rice starches but increased the longer chain fraction and decreased the shorter chain fraction of potato starch, as measured by high-performance size-exclusion chromatography. Acid-thinned potato starches produced much firmer gels than did acid-thinned corn and rice starches, possibly due to potato starchs relatively higher percentage of long branch chains (degree of polymerization 13—24) in amylopectin. The short-term development of gel structure by acid-thinned starches was dependent on amylose content, whereas the long-term gel strength appeared dependend on the long branch chains in amylopectin.

Structures and rheological properties of corn starch as affected by acid hydrolysis

Abstract Common corn starch was treated with different concentrations of hydrochloric acid, 0.06, 0.14, and 1.0N, for different lengths of time, 18, 6, and 1xa0h, respectively, to reach a similar peak viscosity as measured by Brabender Viscoamylograph. The fine structures, crystallinity and thermal properties were characterized and the rheological properties were evaluated using both compression and dynamic oscillatory tests. Acid hydrolysis had little effect on amylopectin branch chain-length distribution, gelatinization and retrogradation properties. However, the higher acid concentration (1.0N) degraded both amylopectin and amylose to a greater extent compared with the other two lower acid concentrations (0.06 and 0.14N). The acid treated starches had slightly higher degrees of crystallinity and lower amylose content than did the unmodified starch. Degradation of amylose and amylopectin by a high acid concentration resulted in a decrease in storage modulus (G′), loss modulus (G″), gelling temperature, and gel strength of the acid-thinned starches.

Structures and Properties of Commercial Maltodextrins from Corn, Potato, and Rice Starches

Commercial maltodextrins derived from corn, potato, and rice starches were characterized for their chemical structures and physicochemical properties. Rice maltodextrin consisted of more low molecular-weight (MW) saccharides and potato maltodextrin consisted of more high MW saccharides. Debranched rice maltodextrin had a significantly higher content of saccharides with degree of polymerization (DP) less than 10. On the other hand, debranched potato maltodextrin had a significantly higher content of saccharides with DP greater than 20. Rice maltodextrin had higher protein and lipid contents and exhibited very high viscosity at 40% concentration, which might be caused by the retrograded amylose contained in rice maltodextrin. It is believed that the longer average chain lengths of potato maltodextrin resulted in greater retrogradation, and the shorter chains in rice maltodextrin resulted in lower maximum freeze-concentrated glass transition temperature. The differences in structure of maltodextrins from different botanical sources determine their physicochemical properties.

Characterization of Acetylated Waxy Maize Starches Prepared under Catalysis by Different Alkali and Alkaline‐Earth Hydroxides

The effects of the catalyst used in acetylation, including sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca(OH) 2 ), on the chemical and physicochemical properties of acetylated waxy maize starch were investigated. The Ca(OH) 2 -catalyzed acetylated starch exhibited a slightly higher pasting temperature and a lower β-amylolysis limit compared with acetylated starch prepared under NaOH or KOH catalysis, but no difference was observed for their thermal properties. The carbohydrate profiles of isoamylase-debranched acetylated starches and their p-limit dextrins were characterized by high-performance size-exclusion chromatography. The Ca(OH) 2 -catalyzed acetylated starch showed a elution profile that was different from those of the other two acetylated starches with a greater proportion of saccharides eluted at a longer retention time. However, the differences in pasting temperature, β-amylolysis limit, and carbohydrate profile among the acetylated starches diminished when ethylenediaminetetraacetic acid (EDTA) was added. The results suggest that calcium might induce intermolecular crosslinking through chelation with oxygen of the anhydroglucose units and this type of crosslinking was promoted in acetylation catalyzed by Ca(OH) 2 .

Comparison of protease digestion at neutral pH with alkaline steeping method for rice starch isolation

Lisolement de lamidon de riz differe des autres methodes disolement, du mais, du ble au de la pomme de terre, en raison des proprietes differentes de ses proteines. Le procede par trempage alcalin presente un rendement de 73 a 85%, mais produit beaucoup deaux residuelles alcalines. Lefficacite dune digestion par la protease acide, neutre ou alcaline a pH neutre est evaluee, cette technique ayant deja montre son efficacite sur lamarante et lavoine.

Structures of Four Waxy Rice Starches in Relation to Thermal, Pasting, and Textural Properties

ABSTRACT Waxy rice starches from three japonica cultivars (Taichung Waxy 1 [TCW1], Taichung Waxy 70 [TCW70], Tachimemochi) and one indica cultivar (Tainung Sen Waxy 2 [TNSW2]) were characterized for chemical and physicochemical properties. The amylopectin structures were different for the four waxy rice starches in terms of degree of polymerization (DP), average chain length (CL), exterior chain lengths (ECL), and distribution of chains, indicating the existence of varietal differences. The order of swelling power was TCW1 > TCW70 > TNSW2 > Tachimemochi; the order of water solubility index was TCW70 > TNSW2 > Tachimemochi > TCW1. The low water solubility index of TCW1 might be ascribed to a high DP. All starches shared similar gelatinization temperatures and enthalpies but showed distinct retrogradation patterns. TNSW2 showed the highest retrogradation rate, followed by TCW2, Tachimemochi, and TCW70. TCW70 exhibited the highest overall pasting viscosity, followed by TNSW2, TCW1, and Tachimemochi. The hard...

Application of High-Intensity Ultrasound and Surfactants in Rice Starch Isolation

ABSTRACT High-intensity ultrasound was evaluated as an alternative method to isolate rice starch without the use of chemicals as in the traditional alkaline steeping method. Surfactants, including sodium dodecyl sulfate (SDS), sodium stearoyl lactylate (SSL), and Tween 80, at 0.1, 0.3, or 0.5% combined with high-intensity ultrasound were also investigated for rice starch isolation. A rice flour slurry (33%) was subjected to sonication for 15, 30, or 60 min at an amplitude of 25, 50, or 75% and at 40 or 50°C. The starch yield was not significantly affected by the treatment temperature and ranged from 46.7 to 76.2% (starch dry basis) after the sonication treatment; the protein and damaged starch contents of the isolated starches were 0.9–1.7% and 3.1–3.5% (dry basis), respectively. The combination of 0.5% SDS and high-intensity ultrasound improved the starch yield to 84.9% with low residual protein, however, little improvement was observed with SSL or Tween 80. The pasting properties of isolated starch as m...

Effects of Modification Sequence on Structures and Properties of Hydroxypropylated and Crosslinked Waxy Maize Starch

The effects of modification sequence on chemical structures and physicochemical properties of hydroxypropylated (HP) and crosslinked (XL) waxy maize starch were investigated. The physicochemical properties, including pasting, gelling, and thermal properties, were studied. The chemical structures of dual-modified starches and their beta-limit dextrins were characterized with high-performance liquid chromatography. The HP-XL starch had higher Brabender viscosity than did the XL-HP starch at both pH 7 and 3; however, both showed similar gelling properties. Significantly higher onset and peak gelatinization temperatures, gelatinization enthalpy, and lower retrogradation were observed for the HP-XL starch. The HP-XL starch also exhibited significantly higher beta-amylolysis limit and higher content of low molecular weight saccharides in its isoamylase-debranched starch, suggesting its structure was more accessible to enzymatic attack than the XL-HP starch. Structural analyses revealed different distribution patterns of modifying groups between the two modified starches. The results indicate that the modification sequence altered the susceptibility to enzymes, changed the locations of substitution, and modified the physicochemical properties of the HP and XL waxy maize starches.

Properties and structures of flours and starches from whole, broken, and yellowed rice kernels in a model study

ABSTRACT The objective of this study was to compare the structure and properties of flours and starches from whole, broken, and yellowed rice kernels that were broken or discolored in the laboratory. Physicochemical properties including pasting, gelling, thermal properties, and X-ray diffraction patterns were determined. Structure was elucidated using high-performance size-exclusion chromatography (HPSEC) and high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The yellowed rice kernels contained a slightly higher protein content and produced a significantly lower starch yield than did the whole or broken rice kernels. Flour from the yellowed rice kernels had a significantly higher pasting temperature, higher Brabender viscosities, increased damaged starch content, reduced amylose content, and increased gelatinization temperature and enthalpy compared with flours from the whole or the broken rice kernels. However, all starches showed similar pasting, gelling, ther...