• Korean Journal of Breeding Science
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• v.42 no.1
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• pp.1-10
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• 2010

Five mutants were investigated at the molecular level to determine the factors responsible for mutated endosperm types. They were classified as high (HA) or low amylose (LA) phenotypes based on the amylose content in endosperm. The five were previously produced from Ilpum and Shindongjin cultivar treated with N-methyl-N-nitrosourea and gamma-ray irradiation, respectively. Analysis of the genomic structure and expression of Granule-bounded Starch Synthase I (GBSSI) genes revealed that mutants generally showed a higher incidence of nucleotide transition than transversion, and the $A:T{\rightarrow}G:C$ transition was particularly prevalent. The rates of nucleotide substitution in HA mutants were generally higher than those in the LA mutants, leading to higher substitutions of amino acid in the HA mutants. Neither nucleotide substitutions interfering with intron splicing or causing early termination of protein translation were found, nor any large-sized deletions or additions were found in all the mutants. In principle, amylose content can be regulated by three factors: internal alterations of GBSSI protein, the strength of gene expression, and other unknown external factors. Our results indicate that the endosperm mutants from Shindongjin arose from internal alterations of GBSSI proteins, which may be the result of amino acid substitutions. On the other hand, the Ilpum mutants might be principally caused by the alteration of gene expression level. Analysis of another three glutinous cultivars revealed that the major factor leading to glutinous phenotypes is the 23-bp duplicative motif (5'-ACGGGTTCCAGGGCCTCAAGCCC-3') commonly found in exon 2, which results in the premature termination of protein translation leading to the production of a non-functional GBSSI enzyme.

• Korean Journal of Food Science and Technology
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• v.28 no.3
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• pp.580-586
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• 1996

Gelatinization behavior and morphology of epichlorohydrin-crosslinked potato starches (XPs) were investigated. Native potato starch showed a very steep single stage swlling pattern, but crosslinked starches showed various patterns with the degree of crosslinking. Swelling power, solubility and light transmittance were reduced drastically as the degree of crosslinking increased. Brabender initial pasting temperature and peak temperature of crosslinked starches increased because the crosslinking reinforces the intermolecular net work of the starches. Although the swelling of the potato starch granule was inhibited by crosslinking as compared to that of the native one, Brabender peak viscosities (6.5% w/v, db) were on the order of 2,500 units for the native potato starch, 3,700 for the XP with 2.300 anhydroglucose units per crosslinking (AGU/CL) and 3,400 for the XP with 2,100 AGU/CL, due to the decreased breakdown of the swollen granule resulting from the resistance to heat and shear. The XP with 1,900 AGU/CL, however, did not show the peak viscosity and the viscosity was on the order of 500 units because of the excessive unhibition of the swelling. Unlike the native potato starch, 6.5%(m/v, db) pastes of the crosslinked potato starches could form gels, which could be predicted from the Brabender setback and consistency index. When the degree of crosslinking is low, random contraction and radial swelling of the granule was possible. As the degree of crosslinking increased, morphological change became similar to the single dimensional tangential swelling observed from the lenticular wheat starch. These morphological change during heating in excess water explained the gelatinization behaviors of crosslinked starches tested.

• Korean journal of food and cookery science
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• v.32 no.3
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• pp.253-260
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• 2016

Purpose: To develop fat-free dressing containing a resistant starch (RS) as a dietary fiber, the viscosity and stability of various type RSes prepared from wheat, maize, potato, rice, waxy rice, and amaranth starches were investigated by using Brookfield viscometer. The shape of RS granule in the dressing during storage was also observed. Methods: The viscosity of fat free dressing with different retrograded RS3 (RS3V) prepared from waxy rice starch with 0.1% lemon vinegar and ascorbate mixed solution had higher RS3 that was maintained constant during storage. Annealing and heating prior to cross-linking, and heating after cross-linking increased RS level of RS4 type starches. Results: The viscosities and stabilities of dressings with RS were different depending on starch sources and RS preparation conditions. The heated RS4 (HRS4) increased in viscosity and stability with RS4 addition. Especially the fat-free dressings with HRS4 prepared from rice and waxy rice starches maintained stability regardless of separation after one month storage with only 7% separation after 6 month storages. The shape of RS4 granule in acidic medium of dressing did not change until 6 months. Conclusion: In this study, RS4 made by the rice and waxy rice starches showed high viscosity and maintained stability of the fat-free dressings during storage.

• Korean journal of food and cookery science
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• v.15 no.5
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• pp.500-506
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• 1999

Scanning electron microscopy was used to study changes in granule shape, dough and cooked noodle structure of pea starch-wheat composite flour with 20% and 30% pea starch substitution. The granule shape of pea starch with low swelling power and solubility was oval, irregular and smooth, which had more a deep groove than corn starch and wheat flour. During gelatinization, pea starch after swelling was partially collapsed but it still held its main shape. The dough microstructure of 20% pea starch substitution showed compact structure distributed with more small starch granules than wheat dough and was held in discontinuous network. When cooked, more open filamentous network where starch gelatinization was complete were noticed. Swollen but partially collapsed large starch granules maintaining their shape were appeared in noodle structure after 30 min soaking in soup. In farinograph studies, 20% pea starch substitution to wheat flour showed that MTI value was as same as wheat flour even though stability was slightly decreased so that it was considered that it has proper property of noodle making.

• Korean Journal of Food Science and Technology
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• v.20 no.3
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• pp.412-418
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• 1988

Granular shapes and sizes, physicochemical priperties and gelatinization patterns of sweet potato starches from Wonki(the dry type) and Chunmi(the moist type) were investigated. Starch granules of sweet potatoes were round. Granule sizes of Wonki starch were mainly $11{\mu}m$ and those of Chunmi starch were $12{\mu}m\;and\;17{\mu}m$. Wonki starch had lower water binding capacity and swelling power than Chunmi starch. But Wonki starch had higher amylose content, gelatinization temperature, miture content for gelatinization and temperature for gelatinization than Chunmi starch.

• Korean journal of food and cookery science
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• v.24 no.3
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• pp.273-281
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• 2008

To determine the nutritional quality and physical properties of ginseng-chicken meat porridge, 10 kinds of ginsengchicken meat porridge samples containing waxy and/or non-waxy rice were analyzed for in vitro protein digestibility and their degree of starch hydrolysis. Viscosity and spreadness were determined for the gelatinized pastes of the porridge samples. Microphotographs of the starch granules and pastes were studied to confirm structural changes in the rice starch during cooking. The starch paste from non-waxy rice porridge had higher viscosity than the starch paste from the waxy rice porridge; however, in the case of the ginseng-chicken meat porridge, the difference in viscosity was negligible. Microphotograph comparisions between the waxy rice porridge and non-waxy rice porridge indicated apparent differences in the shapes of their starch granules and gels. The granule surface of the non-waxy rice was very rough while that of the waxy rice was very smooth; this difference would lead to organoleptical discrepancy. The added ginseng increased the protein digestibility of the chicken meat; however, the protein digestibility of the ginseng-chicken meat porridge was lower than that of the chicken meat or rice porridge due to inhibited protein digestion by the gelatinized starch. Finally, the rice porridge had increased starch hydrolysis with additions of chicken meat and vegetables.

• 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 Food Science and Technology
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• v.39 no.6
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• pp.637-643
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• 2007

In this report, we discussed the physiochemical characteristics of corn starch during the alkali gelatinization process. Here, solubility and the amounts of eluted polysaccharides and amyloses increased in proportion to the amount of alkali added. The X-ray diffraction patterns and DSC thermogram showed that in the early stage of alkali gelatinization, crystallinity of the starch granules was disrupted as compared with heat gelatinization. This resulted in the eluted amylose content, while granule sizes were hardly changed in the alkali treated corn starch. The endotherm peak in the DSC thermogram shifted toward a higher temperature region as the degree of gelatinization increased, suggesting that the retained starch granules were more compactly crystallized during alkali gelatinization than during the heat process. Thus, we concluded that during the alkali gelatinization of corn starch, the disruption of weak particles would occur first, before swelling of the granules.

• Korean Journal of Food Science and Technology
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• v.37 no.3
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• pp.438-442
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• 2005

Granule swelling is essential phenomenon of starch gelatinization in excess water, and characteristic of heated starch dispersion depends largely on size and distribution of swelled starch granule. Although swelling characteristic of starch granules depends on type of starch, heating rate, and moisture content, influence of heating rate on swelling phenomenon of starch granule has not been fully discussed, because constant heating rate of starch dispersion cannot be obtained by conventional heating method. Ohmic heating, electric-resistant heat generation method, applies alternative current to food materials, through which heating rate can be easily controlled precisely and conveniently at wide range of constant heating rates. Starch dispersion heated at low heating rates below $7.5^{\circ}C/min$ showed Newtonian fluid behavior, whereas showed pseudoplastic behavior at heating rates above $16.4^{\circ}C/min$. Apparent viscosity of starch dispersion increased linearly with increasing heating rate, and yield stress was dramatically increased at heating rates above $16.4^{\circ}C/min$. Average diameter of corn starch granules during ohmic heating was dramatically increased from $30.97\;to\;37.88\;{\mu}m$ by increasing heating rate from $0.6\;to\;16.4^{\circ}C/min$ (raw corn starch: $13.7\;{\mu}m$). Hardness of starch gel prepared with 15% corn starch dispersion after heating to $90^{\circ}C$ at different heating rates decreased gradually with increasing heating rate, then showed nearly constant value from $9.4\;to\;23.2^{\circ}C/min$. Hardness increased with increase of heating rate higher than $23.2^{\circ}C/min$.

• Korean Journal of Food Science and Technology
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• v.28 no.3
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• pp.573-579
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• 1996

Crosslinked potato starches (XP), from 2,400 to 1,900 anhydroglucose units per crosslinked (AGU/CL), were prepared by reacting with epichlorohydrin. Some of the physicochemical properties of the XPs were then compared with those of native potato and cowpea starches. Crosslinking decreased moisture, protein and ash contents but had no effect on phosphorus content. Water binding capacities of the XPs increased as the degree of crosslinking increased, and that of the XP with 2,100 AGU/CL approached the value of cowpea starch. The absorption maxima of the starch-iodine complex shifted from 594 to 580 nm. Granule size increased slightly and surface appearance of the granule became rough when crosslinked. Both native and crosslinked potato starches showed B type X-ray diffraction pattern, and the relative crystallinity was not affected by crosslinking. Gelatinization temperature and the heat of gelatinization, measured by differential scanning calorimeter (DSC), did not change within the range of crosslinking tested. From X-ray and DSC data, it was concluded that the crosslinking ocurred in the amorphous region of the starch granule.