• Journal of Microbiology
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• v.37 no.2
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• pp.80-85
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• 1999

The purification system of glucoamylase (glucan 1,4-${\alpha}$-glucosidase, EC 3. 2. 1. 3), some characteristics of the purified enzyme and hydrolysis rate of various raw starch were investigated through several experiments. The enzyme was produced on a solid, uncooked wheat bran medium of Aspergillus oryzae NR 3-6 isolated from traditional Korean Nuruk. The enzyme was homogeneously purified 6.8-fold with an overall yield of 28.3% by the criteria of disc- and SDS-polyacrylamide gel electrophoresis. The molecular weight was estimated to be 48 kDa by SDS-PAGE. The optimum temperature and pH were 55$^{\circ}C$ and 4.0, respectively. The enzyme was stable at a pH range of 3.0∼10.0 and below 45$^{\circ}C$. Enzyme activity was inhibited about 27% by 1mM Hg2+. The hydrolysis rate of raw wheat starch was shown to be 17.5-fold faster than the hydrolysis rate of soluble starch. The purified enzyme was identified as glucoamylase because the product of soluble starch by the purified enzyme was mainly glucose by thin layer chromatography.

• Food Science and Biotechnology
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• v.14 no.4
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• pp.470-473
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• 2005

Starch was isolated from turnip (Brassica rapa L.), and to elucidate the structure-function relationship its structural and physical properties were characterized. Morphological structure of the starch was analyzed by SEM (Scanning Electron Microscopy). Most of the starch granules were spherical in shape with diameter ranging from 0.5-10mm. Apart from larger granules ($<10\;{\mu}m$) which dominated the population size of turnip starch, significant amount of small ($0.5-2\;{\mu}m$) and mid-size granules (${\sim}\;{\mu}m$) were also detected. It was revealed that presumably, erosion damages occurred due to the attack of amylase-type enzymes on the surface of some granules. Branch chain-length distribution was analyzed by HPAEC (High-Performance Anion-Exchange Chromatography). The chain-length distribution of turnip starch revealed a peak at DP12 with obvious shoulder at DP18-21. The weight-average chain length ($CL_{avg}$) was 16.6, and a large proportion (11.8%) of very short chains (DP6-9) was also observed. The melting properties of starch were determined by DSC (Differential Scanning Calorimetry). The onset temperature ($T_o$) and the enthalpy change (${\Delta}H$) of starch gelatinization were $50.5^{\circ}C$ and 12.5 J/g, respectively. The ${\Delta}H$ of the retrograded turnip starch was 3.5 J/g, which indicates 28.2% of recrystallization. Larger proportion of short chains as well as smaller average chain-length can very well explain relatively lower degree of retrogradation in turnip starch.

• Korean journal of food and cookery science
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• v.32 no.4
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• pp.524-530
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• 2016

Purpose: The properties of starch and starch gel prepared from a newly inbred sweet potato, Daeyumi were compared to the properties of starch and starch gel prepared from Sinyulmi which is a well known mealy type sweet potato. Methods: The starch was isolated by using the alkaline steeping method. Physicochemical, pasting, and thermal properties, and crystallinity were measured. The texture properties of starch gel (10%, w/w) were examined. Results: The amylose contents of Daeyumi and Sinyulmi starches were 25.57% and 22.59%, respectively. The initial pasting temperature of Daeyumi starch was significantly higher than that of Sinyulmi starch (p<0.05), but other paste viscosities were not different. The peak and conclusion temperatures of Daeyumi starch were higher than those of Sinyulmi starch by differential scanning calorimetry. The shape of Daeyumi starch gel was more clear and rigid than the shape of Sinyulmi starch gel. The surface and the upper side of Daeyumi starch gel were smoother than the surface and the upper side of Sinyulmi starch gel. Hardness and gumminess were higher in Daeyumi starch gel than in Sinyulmi starch gel. The crystallinity types of Daeyumi and Sinyulmi starches were $C_b$ and A types, respectively, but starch gels showed an amorphous type. Conclusion: Therefore, it is suggested that Daeyumi starch would have better physicochemical properties and higher quality of starch gel than Sinyulmi starch.

• Journal of Conservation Science
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• v.24
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• pp.67-74
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• 2008

The objective of this study was to investigate stability of traditional starch sizes according to time. The properties of wheat flour and fermented whole-wheat flour were studied. And comparison of stiffness, tensile strength, air permeability, whiteness, and surface observation of cotton fabrics sized with wheat flour and fermented whole-wheat flour before and after 12-years were examined. The amylograph data indicated that ISF-W(Isolated starch flour- white) have good pasting properties than NWF(Natural wheat flour) and ISF-B(Isolated starch flour- light brown). The cotton fabrics sized with ISF-W had higher tensile strength and whiteness, and lower stiffness and air permeability than those of NWF as the time takes 12 years. We identified the stability of traditional starch size using scanning electronic micrograph.

• Korean Journal of Human Ecology
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• v.14 no.6
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• pp.1037-1046
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• 2005

Using three consecutive years' harvested rices and their starches isolated from rice flours by alkaline method, it was found that no significant aging effect on rice flour and starch was observed based on following results. Proximate data of flours or starches showed in similarity, except high level of crude fat in rice flour and rice starch harvested in 2002. In SEM, the surface of aged rice flour had slightly layered shape due to possible abrasion during storage, and that of aged starch showed more smooth and less rigid polygonal shape. X-ray diffraction patterns of flours and starches were all A type, and crystallinity of rice starch harvested in 2000 had the smallest. From tristimulus colorimetry (Hunterlab Color), total color difference ($\Delta$E) calculated from L, a, and b gave less color difference with the darkest in 2002 harvested one among flours and the lightest in 2001 one among starches. WBCs of both 2002 rice flour and starch were the lowest among samples studied. At 80$^{\circ}C$, swelling power and solubility of rice starches harvested in 2000, 2001 and 2002 were 14.35, 9.75; 14.04, 9.6; and 12.49, 8.82, respectively. The highest peak viscosities measured by RVA were shown both in 2001 rice flour and in its starch. Starch and milled rice flour harvested in 2000 had higher hydrolytic $\alpha$-amylase, compared to other flour and starch samples.

• 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.

• Journal of Microbiology and Biotechnology
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• v.3 no.2
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• pp.99-107
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• 1993

Two strains (No. 26 and 143) of bacteria which secrete both pectinase and raw-starch-digesting amylase simultaneously, were isolated from various domestic soil samples. The two bacteria were identified as Pasteurella ureae judging by their morphological and physiological characteristics. The optimal culture conditions for the production of raw-starch-digesting enzyme by the Pasteurella ureae 26 were using $NH_4NO_3$ as the nitrogen source at $37^{\circ}C$ with the pH of 7.5, and 15 of C/N ratio. Since the enzyme was produced only when raw or soluble starch was used as a carbon source, but not when glucose or other sugars was used, the enzyme was considered to be an inducible enzyme by starch. Thin layer chromatography of the hydrolyzed product of starch by the raw-starch-digesting enzyme of the strain No. 26 showed that glucose, maltose and other oligosaccharides were present in the hydrolyzates, and therefore the enzyme seemed to be ${\alpha}-amylase$. The enzyme had adsorbability onto raw com starch in the pH range of 3 to 9.

• Applied Biological Chemistry
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• v.29 no.4
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• pp.339-345
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• 1986

Rheological characteristics of starch isolated from germinated corn were investigated and compared with those of nongerminated corn starch. Flow behavior of both starches were Bingham psudoplastic. Consistency index and yield stress of germinated starch solution were lower than those of nongerminated starch solution, while flow behavior index was nearly similar. Concentration dependency of both starch solutions were similar to each other but lower temperature dependency of germinated starch solution was observed. Time dependent characteristics of both starches showed thixotropic behavior, but due to germination, germinated starch showed higher structural decay under shear than nongerminated starch and its elastic properties was weaker.

• Applied Biological Chemistry
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• v.29 no.4
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• pp.333-338
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• 1986

Physicochemical properties of starch isolated from germinated corn were investigated and compared with those of nongerminated corn starch. Amylose content and initial gelatinization temperature of germinated starch were lower than those of nongerminated starch. Swelling power and solubility of both starches exhibited two stage behavior, however germinated starch revealed lower swelling power and higher solubility compared to those of nongerminated starch. Both starches showed a typical A type X-ray diffraction and irregular oval shape including partly polygon with the size of $10-25{\mu}m$. However, germinated starch showed many holes with the size of $1-2{\mu}m$ on the surface of granule.

• Korean Journal of Human Ecology
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• v.19 no.1
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• pp.191-201
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• 2010

This study attempted to examine the application of retrograded starch (RS3) isolated from rice flour into Madeleine which is easy to make, supply enough energy and micro nutrients with adequate drinks, and prevent an adult disease. This could be a popular food to anyone regardless of age and gender who avoid rice and become high value-added, processed rice foods. For this, control Madeleine was made from wheat flour and an experimental one was made from 5 or 10% rice RS3 addition as well as wheat flour. Four different types of rice were produced from Premium Ho-Pyong Rice, that is, dry milled rice flour(RFD), soaked for 8 hours and milled, followed by air-dried rice flour(RFW), rice starch(RST), and retrograded rice starch or enzyme-resistant starch(RS3). The results found were as follows: Proximate compositions were decreased with soaking to make RFW, RST and RS3, compared to RFD. RS3 had the highest L, +a and ${\Delta}E$ with the lowest +b, changing it to a dark color, explaining the need for heat control during processing. At $80^{\circ}C$, the swelling power was shown in the order of RST>RFW>RFD>RS3 and the solubility of RS3 was the highest. There were significant differences in viscosities of peak, trough, cold, breakdown and total setback of all rice samples using RVA (p<0.001). Due to the pH of RS3, the Madeleine batter became acidic (p<.01) and expanded, resulting in more air cells and open texture. With an increasing RS3 level in Madeleine, several textural attributes among 'fresh' and 'stored at room temperature' Madeleine samples were significantly different by using Texture Analyzer. While the addition of RS3 in Madeleine did not significantly affect the sensory evaluation, indicating RS3 isolated from rice as a beneficial ingredient for processed rice products.