• Applied Biological Chemistry
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• v.38 no.4
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• pp.353-358
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• 1995

The influence of dry-heat treatment($130{\sim}220^{\circ}C$) on the gelatinization and rheological properties of corn starch(11.4% moisture) was examined. The enthalpy of gelatinization measured by differential scanning calorimetry decreased above $190^{\circ}C$. The viscosity of starch by alkali gelatinization increased as the heating temperature rised. All the values including peak viscosity on amylograms and shear stress, apparent viscosity, consistency index and yield stress of thermal-gelatinized starch dispersion showed decreasing tendencies with increasing of heating temperature from above $170^{\circ}C$ compared with those of raw starch. The apparent viscosity and yield stress of all the samples thermal-gelatinized at $90^{\circ}C$ were increased considerably with process of gelatinization time and especially their rapid increase at the early stage was observed in the $190^{\circ}C$ sample. But all the rheological parameters of $220^{\circ}C$ sample recorded very low values compared with those of the others.

• Korean Journal of Food Science and Technology
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• v.24 no.6
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• pp.619-622
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• 1992

To increase utilization of Korean yam, the rheological properties of gelatinized yam (Dioscorea aimadoimo) starch solutions at various concentrations $(1{\sim}5%)$ and temperature $(30{\sim}60^{\circ}C)$ were investigated. The rheological behavior of gelatinized yam starch solutions was illustrated by power-law model and Casson equation and exhibited pseudoplastic behavior with yield stress. The pseudoplasticity of starch solutions increased largly concentration of starch increased. As the temperature increased from $30^{\circ}C$ to $60^{\circ}C$, the dependency of starch concentration decreased, B were decreased from 0.40449 to 0.39352. The activation energy of flow of gelatinized yam starch solutions were increased from 4.1415 to $5.45329{\times}10^6\;J/kg{\cdot}mol$ by increasing starch concentration from 1% to 5%.

• Korean Journal of Food Science and Technology
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• v.36 no.6
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• pp.952-958
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• 2004

Effects of normal (non-waxy) and waxy millet flours on properties of sponge cake were examined. Total dietary fiber contents of normal and waxy millets were 5.04 and 5.12%, respectively, while that of soft wheat flour was 2.23%. Alkaline water retention capacity value generally increased with addition of normal and waxy millet flours, whereas peak, minimum, and final viscosities decreased. Mixing time and mixing height decreased with addition of millet flour. Lightness of cake crust increased with addition of normal millet flour, whereas it decreased with addition of waxy millet flour, tightness of cake crumb decreased as the amount of normal and waxy millet flours increased. Increasing proportions of normal and waxy millet flours resulted in significantly decreased loaf volume. Replacement of 10% wheat flour by both normal and waxy millet flours did not significantly affect characteristics of sponge cake, but addition of more than 20% millet flour resulted in significant differences in quality characteristics.

• Korean Journal of Food Science and Technology
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• v.16 no.4
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• pp.451-456
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• 1984

Rheological properties of gelatinized rice starch solutions were investigated with Brookfield rotational viscometer. The 8% starch solution showed thixotropic behavior with yield stress. The alkali gelatinized starch was more thixotropic than the thermal gelatinized one. The time dependent characteristics of starch solutions followed Tiu's model. The value of rate constant $(a_1)$ in Tiu's model increased linearly with shear rate, and was exponentially dependent on concentration and temperature. Temperature dependency of rate constant and apparent viscosity followed Arrhenius type equation and the activation energy were about 14.3 and 6.8 Kcal/g mole, respectively. The $a_1-value$ was found to be useful to evaluate changes in structaral decay on the shearing time of gelatinized rice starch solutions.

• Korean Journal of Food Science and Technology
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• v.20 no.3
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• pp.392-398
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• 1988

Gelatinized rice flours were prepared by drum drying at different moisture contents of slurry made from dry milled and wet milled rice flours. Milled rice samples were prepared from the Chuchung and the Samgang varieties. Degree of gelatinization of drum-dried rice flours revealed over 92% at 60% moisture content of wet milled rice flours and 80% moisture content of dry milled ones. With regards to amylogram and rheological properties, drum-dried rice flours prepared from wet milled raw materials showed higher viscosity than from dry milled ones. Increasing water contents in the slurry increased water absorption index(WAI) and decreased water solubility index(WSI). Hunter's color values of drum-dried rice flour at high moisture contents showed higher L values and lower b values. For the preparation of gelatinized rice flours by drum drying process, the higher water content caused more gelatinized network structure of rice starch in scanning electron micrographs. With regards to farinogram properties of dough with drum-dried rice flours and wheat flours in mixing ratio of 1 to 9 by weight, drum-dried rice flours made from wet milled raw rice flours revealed higher MTI than from dry milled ones.

• Korean Journal of Food Science and Technology
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• v.21 no.6
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• pp.800-807
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• 1989

No-time dough process utilizing ascorbic acid as an oxidant was investigated. The farinograph absorption was increased as the amount of L-cysteine increased, while stability and peak time decreased up to 40 and 30 ppm of L-cysteine, respectively. Extensibility of the dough was increased with the increment of L-cysteine, but the ratio of resistance to extensibility was significantly decreased. At the same level of L-cysteine, the addition of ascrobic acid by 1.5 times decreased the farinograph absorption. However, the stability and peak time remained relatively unchanged upon addition of ascrobic acid. Extensibility and resistance of dough were respectively decreased and increased in the presence of both L-cysteine and ascorbic acid. In the range of 30-50 ppm of cysteine, the mixing time decreased and the baking absorption was increased by 1% as the cysteine was increased by 10 ppm. The ascorbic acid had no effects on absorption and mixing time. Bread produced by no·time dough process had no break and shred. The optimum concentrations of L-cysteine and ascorbic acid for no-time dough process were 40 and 100ppm, respectively.

• Korean Journal of Food Science and Technology
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• v.35 no.5
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• pp.918-923
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• 2003

Replacement of wheat flour by 10, 20 30% waxy and normal (non-waxy) hull-less barley flour was tested for the effects on bread-making properties. The addition of waxy hull-less barley flour resulted in lower amylograph pasting temperature, peak, and set back viscosities and in higher water absorption, compared with normal hull-less barley flour. Increasing proportions of hull-less barley flour significantly decreased the loaf volume and had deleterious effects on subjective bread scoring. Replacement of 10% of wheat flour by both waxy and normal hull-less barley flour did not significantly affect bread characteristics. However, significant differences in bread quality were observed between the control bread and bread containing more than 20% barley flour, with the normal barley flour showing slightly better scores in organoleptical preference. Textural measurements of crumb firmness showed that the bread containing 20% waxy hull-less barley flour hardened slower during 5-day storage at $25^{\circ}C$ than bread containing normal hull-lee barley flour.

• Korean Journal of Food Science and Technology
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• v.20 no.4
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• pp.470-475
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• 1988

The extrusion-cooking method was used to make gelatinized rice extrudate from rice grits of the Chuchung and the Samgang varieties. The water contents of raw rice grits varied from 15% to 25%, and the physicochemical properties of extrudates were evaluated. Low moisture content showed high expansion ratio in rice extrudate and resulted in some decrease in gelatinization, bulk density and break strength. Increasing the water content to 25% resulted in increase in water absoption index but decrease in water solubility index. With regards to Brabender Amylograph values and rheological patterns, higher moisture content in raw materials revealed stronger pseudoplastic flow behavior with lower viscogram property. Hunter's color values of rice flours extruded at low water content were low in b values. Scanning electron microscopy demonstrated the break-down of starch granules during extrusion.

• Korean Journal of Food Science and Technology
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• v.36 no.5
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• pp.749-753
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• 2004

Effects of olive oil on rheological properties of wheat flour dough were investigated through farinograph, amylograph, and extensograph, and by measuring wheat flour dough fermentation volume. Farinogram showed development time, stability, elasticity, and valorimeter value of olive oil-added wheat flour decreased, whereas water absorption and stability were similar to control (shortening 4%). Gelatinization temperature and maximum viscosity of wheat flour dough with olive oil decreased more than those of control as revealed by amylogram. Extensogram showed wheat flour area increased, whereas dough volume decreased in olive oil-added wheat flour dough.

• Korean Journal of Food Science and Technology
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• v.36 no.5
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• pp.795-799
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• 2004

Noodles were prepared by adding 25, 50, 75, and 100% wax gourd juice to wheat flour, and effects of added wax gourd juice on dough rheology and cooking and noodle qualities were examined. Initial pasting temperature, and peak and final viscosities increased with addition of wax gourd juice. Water absorption and dough weakness, and cooked weight, moisture absorption, cooked volume, and cooking loss of noodleincreased, but dough development time and dough stability decreased with increase in wax gourd juice content. Hardness, cohesiveness, and gumminess of cooked noodles increased significantly with increase in war gourd juice content. Sensory evaluation results reveal noodles containing 25 and 50% wax gourd juices have higher qualities than other types.