• Korean Journal of Food Science and Technology
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• v.24 no.2
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• pp.165-170
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• 1992

The creep behavior of gels made with $30{\sim}45%$ gelatinized rice starch was measured over a wide range of temperature. Compressive creep curves of rice starch gels conformed to a six element mechanical model consisting of one Hookean, two Voigt and one Newtonian component. The creep compliance of gels decreased with increasing starch concentrations. Among viscoelastic constants of the mechanical model, elastic modulus was mainly influenced by the change of starch concentrations. The concentration-invariant compliance curve was obtained by reduction to 38% using reduction parameter $a_{c}$. The creep compliance curves of 45% starch gels increased with temperature, which indicated that rice starch gels became softer and less rigid with increasing temperature. When the compliance at $20^{\circ}C$ was set as a reference curve, creep compliance data for 45% gels at various temperature could be superimposed as a continuous smooth curve. The apparent activation energies of 45% rice starch gels calculated by the modified WLF equation were not intrinsic, but decreased as temperature increased.

• Food Engineering Progress
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• v.14 no.2
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• pp.127-134
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• 2010

This study was to develop high-nutritious energy bar from extruded hemp obtained by extrusion process. Mixture of rice flour and defatted hemp was extruded at a barrel temperature of 110 and 130$^{\circ}C$, and moisture content of 20 and 25%. Properties of extrudates such as bulk density, expansion index, breaking strength, apparent elastic modulus, water absorption index (WAI), water solubility index (WSI) have been analyzed. The antioxidant potential was determined by the DPPH-radical scavenging assay. The expansion index was the highest in rice-hemp extrudate at 130$^{\circ}C$ barrel temperature and 20% moisture content among the other hemp-added extrudates. The WAI was increased with increase in moisture content, while the WSI was increased with increase in barrel temperature. The peak viscosity of rice extrudate had higher valule than those of extrudate added with hemp. DPPH scavenging activity of rice-hemp extrudate at 130$^{\circ}C$ barrel temperature and 20% moisture content showed the highest value. Sensory properties, moisture content and color were assessed for quality of energy bar. The color values of the energy bar indicated decreasing L (lightness) and b (yellowness), and increasing a (redness) after 30 days storage at ambient condition. The highest overall acceptable was the energy bar added with rice-hemp extrudate at 130$^{\circ}C$ barrel temperature and 20% moisture content.

• Food Engineering Progress
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• v.21 no.2
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• pp.116-125
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• 2017

This study aims to make extruded rice snack with high quality in texture and nutrition by adding mealworm. Addition of the mealworm has the merit to fill in high-quality protein and unsaturated fatty acids which are insufficient in rice. Thus, the physicochemical properties were investigated through the process of extrusion cooking. As the extrusion process varied, the die temperatures were set to $120^{\circ}C$ and $130^{\circ}C$. Also, the moisture contents were adjusted to 30% and 35%. The specific length, the expansion ratio, and the water absorption index increased as the added content of mealworm became higher. On the contrary, the density, the breaking strength, the apparent elastic modulus, and the water solubility index decreased. As mealworm and moisture content increased, DPPH radical scavenging activity significantly increased but the rancidity decreased. As a result, the addition of mealworm to the extruded rice snack was effective in improving texture, nutrition, and antioxidation.

• Food Engineering Progress
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• v.23 no.2
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• pp.118-124
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• 2019

This study aims to investigate the physical properties of extruded psyllium husk upon the addition of emulsifiers. Three different emulsifiers-glycerol monostearate (GMS), polyglycerol ester (PGE), and sugar ester (SE)-were added to the mixture of psyllium husk and rice powder before extrusion. Extrusion was performed using a twin-screw extruder at 140℃ die temperature, 200 rpm screw speed, and 16% feed moisture content. The physical properties of psyllium husk extrudates including expansion ratio, specific length, piece density, texture profile, color properties, water soluble index, and water absorption index were evaluated. It was observed that the expansion ratio was the highest while the specific length and piece density were the lowest in the control which had no emulsifiers. Texture profile analysis showed that the apparent elastic modulus and breaking strength were highest in the extrudate with a PGE of 0.1%. The adhesiveness was found to be lowest in the extrudates with an SE of 0.1% and GMS of 0.5%. Lightness value was highest in the extrudate with a PGE of 0.1%. Color difference, water soluble index, and water absorption index were highest in the control. The results reveal that some physical properties of extruded psyllium husk were improved with the addition of emulsifiers. This finding provides useful information for the development of psyllium snacks with good physical characteristics.

• Food Engineering Progress
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• v.23 no.4
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• pp.283-289
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• 2019

This study was performed to determine the effect of psyllium husk addition on the physical properties of rice extrudates. Rice-based formulations mixed with psyllium husk (0, 7, 14 and 21%) were extruded at a die temperature of 140℃, screw speed of 200 rpm, and moisture content of 20%. As the content of psyllium husk increased, expansion ratio decreased, while piece density and specific length increased. Apparent elastic modulus, breaking strength, adhesiveness, and hardness augmented with an elevation in psyllium husk content. Lightness declined as psyllium husk content furthered, while redness, yellowness, and color difference intensified. Water soluble index and water absorption index increased with an increased amount of psyllium husk. In conclusion, the addition of psyllium affected the expansion of extruded rice snack possessing hard texture, small cells, and sticky texture due to higher water absorption during hydration.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.6
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• pp.921-927
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• 2015

The aim of this study was to investigate the effect of die temperature and repeated extrusion on physical properties of extruded white ginseng (EWG). The die temperature was adjusted to 100, 120, and $140^{\circ}C$, and extrusion was repeated under the same conditions with their corresponding samples. Specific mechanical energy input decreased as die temperature increased during extrusions. The secondary extruded white ginseng (SEWG) at a die temperature of $120^{\circ}C$ showed a higher expansion index than other extrudates. Elevation of both die temperature and repeated extrusion increased the specific length of extrudates. The highest apparent elastic modulus, breaking strength, and water solubility index obtained from SEWG at a die temperature of $100^{\circ}C$ were $7.53{\times}10^8N/m^2$, $7.49{\times}10^5N/m^2$, and 39.02%, respectively. When die temperature increased, water absorption index (WAI) decreased. The WAI of SEWG was higher than that of EWG. In conclusion, repeated extrusion affected physical properties of white ginseng and could be applied to produce improved quality of ginseng products.