• Polymer(Korea)
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• v.28 no.6
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• pp.519-523
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• 2004

Starch was grafted with maleic anhydride by melt process and then the grafted starch was blended with poly(lactic acid). The thermal properties of the poly(lactic acid), poly(lactic acid)/starch, and poly(lactic acid)/ modified starch were observed by DSC and TGA analysis. In the case of poly(lactic acid)/modified starch, an additional melting peak at 1$65^{\circ}C$ accompanying with 172$^{\circ}C$ assigned to pure poly(lactic acid) melting transition was clearly displayed in DSC analysis. Also, smooth decomposition pattern between starch and poly(lactic acid) was also monitored in poly(lactic acid)/modified starch blend by TGA analysis. The modulus of poly(lactic acid)/modified starch was 12％ higher than that of poly(lactic acid)/starch. The thermal and mechanical characteristics of poly(lactic acid)/modified starch might be due to the enhanced compatibilization between each components, which was also observed in SEM analysis.

• Food Science and Biotechnology
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• v.18 no.5
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• pp.1145-1149
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• 2009

Physicochemical properties of native and acid-modified Job's tears (Coix lachryma-jobi L.) starches were investigated. Starch extracted from Job's tears was treated with 2.2 N hydrochloric acid for different length of time (3, 6, 12, and 18 hr). The hydrolysis pattern of starches with the acid proceeded rapidly up to 12 hr and then the approached constant values. The swelling power of acid-modified starches measured at all temperatures was lower than that of its native counterparts and the water solubility index increased as temperature and hydrolysis time increased. Rapid visco analyzer viscograms of acid-modified starches demonstrated a very low viscosity as compared with that of native starch. However, Xray diffraction did not show any significant alteration in the crystallinity after acid-modification.

• Food Science and Biotechnology
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• v.17 no.4
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• pp.755-760
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• 2008

The aim of this study was to produce resistant starch preparations from acid-modified com starches prepared at various hydrolysis levels (0.5-4.0 hr). Effect of autoclaving cycles on resistant starch (RS) formation was investigated. Molecular weight distribution, pasting and functional properties of acid-modified com starches were determined. For RS formation native and acid-modified starch samples were gelatinized and autoclaved (1 or 2 cycles). While native and acid-modified starches did not contain any RS, the levels increased to 9.0-13.5% as a result of storage at $95^{\circ}C$ after first autoclaving cycle. Second autoclaving cycle together with storage at $95^{\circ}C$ brought final RS contents of the samples incubated at 4 and $95^{\circ}C$ after the first cycle to comparable level. As acid modification level increased, the amount of high molecular weight fractions decreased, resulting in significant decreases in viscosities (p<0.05). The samples produced in this study had low emulsion stability and capacity values.

• Korean Journal of Food Science and Technology
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• v.27 no.6
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• pp.1028-1034
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• 1995

Acid-modified and cross-linked chestnut starch properties and their gel properties were examined. Hardness and cohesiveness of acid-modified starch gels were all reduced as acid treatment time was increased. And hardness of crossed-linked starch gels were increased but cohesiveness were not significantly different. Reduction rate of transmittance in acid-modified starch suspensions were higher than that of unmodified starch suspension. Hardness changes of cross-linked starch gels during 4 days of storage were little, especially in the gels made at $75^{\circ}C\;and\;85^{\circ}C$ of heating temperatures.

• Composites Research
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• v.35 no.6
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• pp.419-424
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• 2022

Using non-biodegradable polymers is a severe environmental problem as they are not recyclable and generate a large amount of waste. Biopolymers, such as starch-based composites, have been considered one of the most promising replacement materials. These eco-friendly materials have the advantage of being low-cost, biodegradable, and obtained from renewable sources. However, as starch tends to be brittle and hydrophilic, it can make these materials unusable when exposed to water and limit its processability for further applications. In this work, a biobased modified starch was grafted using two bioderived materials, lauryl methacrylate (LMA) and tetrahydrofurfuryl methacrylate (THFMA), by radical polymerization. A polylactic acid (PLA) composite based on the modified starch (m-St) was fabricated to enhance its toughness. These samples were characterized by Fourier transform infrared, ¹H NMR and ¹³C NMR analysis, optical and scanning electron microscopy. The starch was successfully grafted, thus improving the compatibility with the PLA matrix. The mechanical properties of these films were also studied. Results from mechanical tests showed a slight enhancement of the mechanical performance of these composites when m-St was added to the PLA matrix. Such behavior is related to the improved dispersion of m-St 1:2 on PLA, confirmed by SEM images showing enhanced compatibility between modified starch and PLA matrix. This indicated excellent properties of the produced composite film for further eco-friendly applications.

• Food Science and Biotechnology
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• v.16 no.6
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• pp.943-947
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• 2007

The acid modification of waxy rice starch was conducted to improve the yugwa production process. The intrinsic viscosity, paste viscosity, and differential scanning calorimetry characteristics of acid modified starch were measured, and bandaegi and yugwa prepared from acid modified starch were evaluated. The intrinsic viscosities of acid thinned starches were 1.48, 1.27, 1.15, and 0.91 mL/g after reaction times of 1, 2, 3, and 4 hr, respectively. The gelatinization enthalpy was reduced from 16.3 J/g in native starch to 15.8, 15.3, 14.7, and 14.5 J/g in acid thinned starches as the time of acid thinning increased. The peak viscosity and final viscosity decreased with increasing the time of acid thinning, but the pasting temperature was slightly increased in acid thinned starches. The hardness of bandaegi from acid thinned starches under high pressure greatly decreased relative to the control, typical yugwa. Yugwa from acid thinned starch under high pressure maintained a homogeneous structure containing tiny and uniform cells similar to that of native waxy rice starch used for typical yugwa. Acid thinning under high pressure appears to be a good alternative to the existing steeping process for better yugwa quality.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06a
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• pp.79-84
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• 2006

In order to improve filler-fiber bonding in paper, starch-filler composites were prepared by a starch-fatty acid complex formation method. These composites were used as a papermaking filler to improve the physical properties of the paper, filler retention and the sizing effect. The solubility of the starch-fatty acid complex in water at different temperatures was measured. The results indicated that the starch-fatty acid complexes have very low solubility in water below $70^{\circ}C$, which can be easily coated on clay surface to modify clay-fiber bonding ability. The clay-starch composite filled handsheets showed that paper strength could increase more than $100{\sim}200%$ compared to untreated clay. It was found that ZDT of the handsheet decreased as the clay content increased when unmodified clay was used, but it increased when the starch-fatty acid composite modified filler was used. It was also found that the presence of fatty acide in the complex increased the water-repellant property of the handsheet, which can be used to aid in sizing during papermaking. Filler distribution and bonding characteristics between the composite and fiber were investigated using Scanning Electron Microscopy(SEM).

• Applied Biological Chemistry
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• v.39 no.1
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• pp.49-53
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• 1996

Acid-modified starch was prepared by treating a warm aqueous starch suspension with dilute mineral acid$(0.2\;N\;HCl,\;45^{\circ}C,\;20\;mim{\sim}1\;h)$. The swelling power and solubility of acid-modified red bean starches increased and the changes occurred at tower temperature. According to gel chromatography of starches, the amylose and amylopectin moieties of red bean starches were not affected very much by hydrolysis conditions used. The elution profiles of soluble carbohydrate showed that the larger molecules were leached as the heating temperature increased. Total amounts of soluble carbohydrate were increased by acid-modification. The gel strength of acid-modified starches at each temperature increased, whereas cohesiveness decreased in acid-modified starch gels except at $85^{\circ}C$.

• Microbiology and Biotechnology Letters
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• v.26 no.2
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• pp.143-150
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• 1998

Many enzymes catalyze a primary reaction and/or secondary reaction. Dextransucrase usually synthesize dextran from sucrose as a primary reaction. The secondary reaction of dextransucrase is the transfer of glucose from sucrose to carbohydrate accepters. We have reacted dextransucrase from Leuconostoc mesenteroides B-742CB with sucrose and starches; granule or gelatinized starches, and Small or Potato starches. The yield of modified starch was ranged from 46% to 72%(s.d.<${pm}$5%) of theoretical depends on various reaction conditions. Modified products were more resistant against the hydrolysis of ${alpha}$-amylase, isoamylase, pullulanase and endo-dextranase than those of native starch. Based on the reactions from enzyme hydrolysis and methylation followed by acid hydrolysis modification of granule starch was more efficient than the modification of gelatinized starch. After modification of granule starch with dextransucrase, there produced a soluble modified starch. After modification the starch granules were fractionated to small size. The positions of glucose substitution of the modified products were determined by methylation followed by acid hydrolysis and analyzed by TLC. The products were modified by the addition of glucose to the position of C3, C4 and C6 free hydroxyl group of glucose residues in the starch.

• Korean Journal of Food Science and Technology
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• v.32 no.1
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• pp.147-153
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• 2000

We could produce algin-like biomaterial of polyiduronan using polyglucuronic acid C5-epimerase with polyglucuronic acid prepared by specific oxidation of primary alcohol groups of four kinds of polysaccharides(corn starch, rice starch, sweet potato starch, and cellulose). The enzyme activity was determined by the modified Dische carbazole methodology with the isolated crude enzyme from the supernatant centrifuged at $100,000{\times}g$ for 1 hr after grinding fresh bovine liver. And then, the optimal substrate, pH, and temperature for the enzyme reaction of polyglucuronic acid C5-epimerase were determined as the oxidized sweet potato starch, 7.0, and $30^{\circ}C$, respectively. Conclusively, it could be possible to epimerize polyglucuronic acid in the oxidized sweet potato starch to polyiduronic acid. Therefore, we could obtain algin-like polysaccharide using the oxidized sweet potato starch and polyglucuronic acid C5-epimerase isolated from bovine liver.