• Korean Journal of Food Science and Technology
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• v.26 no.5
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• pp.638-643
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• 1994

Gelatinization and retrogradation properties of modified starches which were prepared by steeping sweet potato at $40^{\circ}C$ for 2, 4, 7 and 10 days were investigated. The peak temperature of gelatinization and enthalpy of untreated starch by DSC were $53.9^{\circ}C\;and\;1.32\;cal/g$, respectively, but those of modified starch were increased by steeping. In gelatinization by alkali, starches with 2, 4 and 7 day steeping showed higher viscosities than untreated starch, whereas the viscosities of starches with 10 day steeping decreased. The clarities in paste decreased during storage in all starches and decreased in starches with steeping. The degrees of retrogradation by ${\alpha}-amylase-iodine$ method were higher in starches with steeping than untreated starch. The enthalpy of retrograded starches by DSC increased by steeping except 4 day steeping starch. The sweet potato extract containing sugar inhibited the retrogradation of starch paste and the degree were higher in residual starches than in untreated starch.

• Food Science and Biotechnology
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• v.17 no.4
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• pp.705-712
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• 2008

Sweet potato starch was modified using Thermus aquaticus $\alpha$-1,4-glucanotransferase ($Ta{\alpha}GT$), and its structural and rheological properties were investigated. $Ta{\alpha}GT$-modified starch had a lower amylose level and molecular weight than raw starch. The chain length distribution showed an increased number of short and long branched chains and the formation of cycloamyloses. Compared with raw starch, $Ta{\alpha}GT$-modified starch displayed a lower gelatinization enthalpy and a wider melting temperature range. The X-ray diffraction of $Ta{\alpha}GT$-modified starch was a weak V-type pattern with distinct sharp peaks at 13 and $20^{\circ}$. Scanning electron micrographs of modified starch exhibited big holes on the surface and the loss of granular structure. The frequency sweep measurement revealed that the gel of $Ta{\alpha}GT$-modified starch was more rigid than raw starch gel. However, the structure of modified starch gel was destroyed by heating at $75^{\circ}C$, and a firm gel was re-formed by subsequent storage at $5^{\circ}C$, indicating thermoreversible property.

• Preventive Nutrition and Food Science
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• v.13 no.3
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• pp.245-248
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• 2008

The effects of native sweet potato starch (NSPS) and sweet potato starch modified by acetylation (MSPS) on dynamic rheological properties of surimi sols were investigated by small-deformation oscillatory measurements. Dynamic frequency sweeps of surimi sols at $10^{\circ}C$ showed that the addition of NSPS and MSPS resulted in a reduction of storage modulus (G') and loss modulus (G"). The tan $\delta$ values (ratio of G"/ G') of all samples were in the range of $0.15{\sim}0.54$ over a wide range of frequency, indicating that all surimi sols are more elastic than viscous. The characteristic G' thermograms of surimi sols during heating from 10 to $90^{\circ}C$ were influenced by the addition of starch. The tan $\delta$ values of all samples were maintained nearly constant above $45^{\circ}C$, showing that the G' is proportional to the G" irrespective of starch effects.

• 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.

• The Korean Journal of Food And Nutrition
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• v.11 no.2
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• pp.159-164
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• 1998

pH stability of sweet potato $\beta$-amylase modified with IO4-oxidized soluble starch was increased at pH 3, 5~9 and 11. And optimum pH was 3 and 5 for modification. Thermal stability of the enzyme modified with IO4-oxidized soluble starch was increased at 6$0^{\circ}C$ for 15 min. pH stability of barley $\beta$-amylase modified with IO4-oxidized soluble starch was increased at 3~4 and 8~11, and more increased at pH 3 and 8~11 in the presence of $\alpha$-cyclodextrin.

• Food Science and Industry
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• v.51 no.1
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• pp.45-60
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• 2018

The starch industry in Korea had been based on sweet potato and potato for long time to produce starches which were used for mainly starch noodle such as cellophane noodle. Because of the poor storage stability, high price, and fluctuation of production by year and year of potatoes, the raw material for the production of starch had been changed to corn in 1970s. Along with this, the mass production system had been established, which enabled the production of various starch-related products including modified starches for food, textile, paper, and other industrial uses, starch sweetners, high fructose corn syrup, and gelatinized starch. In this paper, a brief background of corn industry in Korea has been described. The production of starch from corn has been emphasized and the future of corn industry in relation with GMO has been suggested.

• Korean Journal of Food Science and Technology
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• v.31 no.2
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• pp.482-487
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• 1999

Periodate-oxidized soluble starch and maltohexaose reacted with ${\alpha}-NH_2$ group of free amino acids and ${\varepsilon}-NH_2$ group of peptidyl lysine. The result shows that periodate-oxidized soluble starch and maltooligosaccharides reacted with protein and formed Schiff base between CHO group of oxidized sugar and ${\varepsilon}-NH_2$ group of surface lysine of protein molecule. Carbon and hydrogen composition of sweet potato ${\beta}-amylase$ modified with oxidized soluble starch increased and it's nitrogen composition decreased. Carbohydrate contents of sweet potato ${\beta}-amylase$ modified with oxidized soluble starch were 13.2% (pentamer), 13.4% (monomer), and with oxidized maltohexaose were 9.7% (pentamer), 9.3% (monomer) by $phenol-H_2SO_4$ method. Alpha-amino group of N-terminal, and ${\varepsilon}-NH_2$ group of lysine, of sweet potato ${\beta}-amylase$ were reacted with oxidized soluble starch by dinitrophenylation were 70% (pentamer), 73% (monomer) and 33% (pentamer), 26% (monomer), respectively, in comparison with native enzyme.

• Korean Journal of Pharmacognosy
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• v.17 no.2
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• pp.134-138
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• 1986

Based on a tracer study, starch phosphorylase was implicated as an agent in the starch synthesis in sweet potato roots. The enzyme was purified from the tissue as a cluster of isozymes with an average mw of 205K (fresh roots) or 159K (roots stored for 3 mon.). On SDS polyacrylamide gel electrophoresis, one large subunit of 98K mw and several small ones of 47${\sim}57K mw were observed. From the mw data and the results of peptide mapping and immunoelectrophoretic blotting using mono- and polyclonal antibodies, it was deduced that a large part of the large subunit was cleaved at the middle part of the peptide chain to give rise to the small subunits, and on storage, the enzyme molecules were further modified by proteolysis. During the course of phosphorylase purification, a proteinaceous inhibitor of the enzyme was isolated. It had a mw of 250K and was composed of 5 identical subunits of 51K mw. In the direction of starch synthesis, the inhibitor showed a noncompetitive kinetics with a Ki of $1.3{\times}10^{-6}\;M$. By immunohistochemical methods, both the enzyme and the inhibitor were located on the cell wall and amyloplast. Crossreacting materials of the inhibitor were present in spinach leaf, potato tuber and rice grain. These findings indicate the wide occurrence of the inhibitor and also imply its possible participation in regulating starch phosphorylase activity in vivo.

• Korean Journal of Food Science and Technology
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• v.33 no.3
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• pp.313-318
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• 2001

Physicochemical properties of starch vermicelli (Dangmyun) made with different starches in laboratory were determined to develop a modified corn starch comparable to sweet potato starch which is highly expensive than corn starch but commonly used for starch vermicelli in Korea. Initial temperatures (Ti) of gelatinization of starch vermicelli made in laboratory measured by differential scanning calorimeter, which were above $60^{\circ}C$, were higher than those of starch vermicelli in the market. Their X-ray diffraction peaks were relatively sharp compared with those of starch vermicelli in the market, which showed that starches were not completely gelatinized during the process of starch vermicelli preparation in laboratory. Initial temperature (Ti) of corn starch vermicelli was decreased by $3^{\circ}C$ by hydroxypropylation but increased by $2.5^{\circ}C$ by oxidation. Hardness and compression slope of sweet potato starch vermicelli and mungbean starch vermicelli, which were $11,726{\sim}12,555\;g/cm^2$ and $29,914{\sim}30,604\;g/cm^2$, respectively, were the highest in the samples and those of waxy corn starch were lowest. Hardness and compression slope of starch vermicelli made with corn starch slightly oxidized in the concentration of 0.5% NaOCl at pH 9.0, $40^{\circ}C$ for 30 min. increased and found to be comparable to those of sweet potato starch vermicelli.

• The Korean Journal of Food And Nutrition
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• v.11 no.5
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• pp.561-564
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• 1998

The stabilizatio of amaylolytic enzyme such as $\beta$-amylase of barley, $\beta$-amylase of wheat, $\beta$-amylase of sweet potato, $\alpha$-amylase of Bacillus licheniformis, $\alpha$-amylase of Aspergillus sp. and $\alpha$-glucosidase of Aspergillus awamori was attained by modification with periodate-oxidized soluble starch. The pH stability of modified enzyme was increased at pH 9 for $\beta$-amylase of sweet potato, pH 3~5 and 8~11 for $\beta$-amylase of barley, pH 2~3 and 7~12 for $\beta$-amylase of wheat and pH 6 for $\alpha$-glucosidase of Aspergillus awamori. Thermal stability increased 17.6% for $\alpha$-amylase of Aspergillus sp. at 6$0^{\circ}C$ for 10min, 30% for $\alpha$-amylase of Bacillus licheniformis at 10$0^{\circ}C$ for 5min and 4.5% for $\alpha$-amylase of sweet potato at 6$0^{\circ}C$ for 10min compared with those of native enzymes.