• Food Science and Preservation
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• v.21 no.4
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• pp.473-482
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• 2014

Changes in quality of mushroom during storage are severe problem that reduce the shelf life of harvested mushrooms. This study investigates the effect of oriental melon peel extracts on maintenance of the quality of mushrooms (Agaricus bisporus). Mushrooms were dipped in solutions (distilled water, DW; 0.1% oriental melon peel extract, OMP; 0.1% ascorbic acid, AA; and OMP+AA) for 3 minutes. After the dipped mushrooms were air-dried at room temperature, they were packaged in a polypropylene (PP) films and stored at $4^{\circ}C$ and $15^{\circ}C$. The changes in the quality of mushrooms were measured in terms of their color, gas composition, firmness, and sensory evaluation during storage at $4^{\circ}C$ and $15^{\circ}C$. The antioxidant and anti-browning activities of oriental melon peel extract were measured with respect to their total polyphenol contents, total flavonoid contents, DPPH, ABTS radical scavenging, copper chelating activity and PPO inhibition activity. The samples that were dipped in all the solutions did not show significant differences in firmness and gas exchange during their storage at $4^{\circ}C$ and $15^{\circ}C$. At both storage temperatures, the OMP solution samples showed highest L value and lowest delta E value. The sensory evaluation showed that during the storage period, the overall acceptability of mushrooms treated with the OMP and OMP+AA solutions was higher than that of the untreated mushrooms. The total polyphenol and flavonoid contents of oriental melon peel extract were $4.81mg\;GAE{\cdot}g^{-1}$ and $1.18mg\;QE{\cdot}g^{-1}$, respectively. The DPPH, ABTS radical scavenging activity, copper chelating activity and PPO inhibition activity of the oriental melon peel extract lower than ascorbic acid. All these results suggest that oriental melon peel extract can be used as a natural browning inhibitor.

• Food Science and Preservation
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• v.20 no.1
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• pp.7-13
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• 2013

Mushrooms have a shorter shelf-life than most vegetables because of their very high respiration rates, sensitivity to enzymatic browning and susceptibility to microbial spoilage. This study was conducted to investigate effects of various packaging materials and precooling on the quality of mushrooms (Agaricus bisporus). Mushrooms were precooled at $4^{\circ}C$ for three hours and packaged using the following packaging materials; 1) polyethylene (PE) film bags of 0.03 mm thickness, 2) polypropylene (PP) film bags of 0.03 mm thickness, and 3) polystyrene (PS) tray+polyvinyl chloride (PVC) wrapper. The physiological changes (weight loss, gas composition, color, firmness, and sensory evaluation) associated with postharvest deterioration were monitored for 17 days at $10^{\circ}C$. The results showed that the PP film bag maintained quality of mushrooms most effectively, especially PP film bags inhibited decreasing firmness. The samples also exhibited smaller decreases in weight loss rate (0.57%) and Hunter L value (84.44) than PS tray+PVC wrapper (7.73%, 82.19) and PE film bags (0.89%, 82.96). Sensory evaluation level in all samples remained relatively constant during the first 5 days of storage. However, PE film bags and PS tray+PVC wrapper showed lower score of flavor, texture and color than PP film bags after 8 days of storage. This study suggested that PP film bag packaging effectively extends shelf-life of mushrooms during storage.

• Food Science and Preservation
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• v.20 no.1
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• pp.97-103
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• 2013

The effects of gamma irradiation at medium dose levels on commercial starches (corn starch/CS, sweet potato starch/SS, and potato starch/PS) were investigated in terms of its color and lipid oxidation. The CS, SS, and PS samples were irradiated at 0, 1.5, 3, 4.5 and 6 kGy by a Co-60 gamma irradiator and used for measuring Hunter's colors and TBA value. Irradiation doses applied did not cause apparent changes in Hunter color parameters between the control and irradiated groups. But, the decrease in lightness (L value) for CS and the increase in both redness (a value) for SS and yellowness (b value) for PS were observed, respectively, thereby resulting in slight increase in overall color difference (${\Delta}E$) upon irradiation. Browning intensity observed with the naked eye for gelatinized starches by irradiation doses was also gradually increased along with irradiation dose, which was more remarkable in SS. The thiobarbituric acid (TBA) values of samples showed a dose-dependant increase with ${\geq}0.9964$ of $R^2$ (p<0.05).

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.5
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• pp.47-56
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• 2008

This study was performed to evaluate the effect of Response modification factors (R-factor) in 3-, 9- and 20- story steel Moment Resisting Frame (MRF) buildings. Each structure was designed using a R-factor of 8, as tabulated in the 2000 International Building Code provision (IBC 2000) and Korea Building Code (KBC) 2008. In order to evaluate the maximum and minimum performance expected for such structures, an upper bound and lower bound design were adopted for each model. Next, each analytical model was designed using different R-factors (8, 9, 10, 11, 12) and four different structural periods with the original fundamental period. For a detailed case study, a total of 150 analytical models were subjected to 20 ground motions representing a hazard level with a 2% probability of being exceeded in 50 years. In order to evaluate the performance of the structures, static push-over and non-linear time history analysis (NTHA) were performed, and displacement ductility demand was investigated to consider the ductility capacity of the structures. The results show that the dynamic behaviors for the 3- and 9-story buildings are relatively stable and conservative, while the 20-story buildings show a large displacement ductility demand due to dynamic instability factors. (e.g. P-delta effect and high mode effect)

• Journal of The Korean Astronomical Society
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• v.36 no.3
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• pp.89-95
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• 2003

Observations of dark matter dominated dwarf and low surface brightness disk galaxies favor density profiles with a flat-density core, while cold dark matter (CDM) N-body simulations form halos with central cusps, instead. This apparent discrepancy has motivated a re-examination of the microscopic nature of the dark matter in order to explain the observed halo profiles, including the suggestion that CDM has a non-gravitational self-interaction. We study the formation and evolution of self-interacting dark matter (SIDM) halos. We find analytical, fully cosmological similarity solutions for their dynamics, which take proper account of the collisional interaction of SIDM particles, based on a fluid approximation derived from the Boltzmann equation. The SIDM particles scatter each other elastically, which results in an effective thermal conductivity that heats the halo core and flattens its density profile. These similarity solutions are relevant to galactic and cluster halo formation in the CDM model. We assume that the local density maximum which serves as the progenitor of the halo has an initial mass profile ${\delta}M / M {\propto} M^{-{\epsilon}$, as in the familiar secondary infall model. If $\epsilon$ = 1/6, SIDM halos will evolve self-similarly, with a cold, supersonic infall which is terminated by a strong accretion shock. Different solutions arise for different values of the dimensionless collisionality parameter, $Q {\equiv}{\sigma}p_br_s$, where $\sigma$ is the SIDM particle scattering cross section per unit mass, $p_b$ is the cosmic mean density, and $r_s$ is the shock radius. For all these solutions, a flat-density, isothermal core is present which grows in size as a fixed fraction of $r_s$. We find two different regimes for these solutions: 1) for $Q < Q_{th}({\simeq} 7.35{\times} 10^{-4}$), the core density decreases and core size increases as Q increases; 2) for $Q > Q_{th}$, the core density increases and core size decreases as Q increases. Our similarity solutions are in good agreement with previous results of N-body simulation of SIDM halos, which correspond to the low-Q regime, for which SIDM halo profiles match the observed galactic rotation curves if $Q {\~} [8.4 {\times}10^{-4} - 4.9 {\times} 10^{-2}]Q_{th}$, or ${\sigma}{\~} [0.56 - 5.6] cm^2g{-1}$. These similarity solutions also show that, as $Q {\to}{\infty}$, the central density acquires a singular profile, in agreement with some earlier simulation results which approximated the effects of SIDM collisionality by considering an ordinary fluid without conductivity, i.e. the limit of mean free path ${\lambda}_{mfp}{\to} 0$. The intermediate regime where $Q {\~} [18.6 - 231]Q_{th}$ or ${\sigma}{\~} [1.2{\times}10^4 - 2.7{\times}10^4] cm^2g{-1}$, for which we find flat-density cores comparable to those of the low-Q solutions preferred to make SIDM halos match halo observations, has not previously been identified. Further study of this regime is warranted.

• Food Science and Preservation
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• v.14 no.3
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• pp.276-280
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• 2007

This study investigated the physicochemical properties of traditional Olbyeossal(Korean-style parboiled waxy rice) and other rices(dried cooked rice, germinated brown rice, and waxy brown rice). Olbyeossal had a moisture content of 12.7% a crude fat level of 1.0%, a crude ash content of 0.9%, and a crude protein value of 6.3%. The color values were 58.63(L value), 0.83(a value) and 21.73(b value). The water adsorption index(WAI) of Olbyeossal was 6.2g/g after 40 min steeping at room temperature, which was much higher than the WAI of the other rices. The hardness of Olbyeossal(10.5 kgf) was higher than those of other rices($7.5{\sim}8.9$ kgf). The initial pasting temperatures of Olbyeossal, dried cooked rice(DCR), germinated brown rice(GBR) and waxy brown rice(WBR) were $39.5^{\circ}C,\;43.5^{\circ}C,\;65.0^{\circ}C,\;and\;64.5^{\circ}C$, respectively. The breakdown and total setback viscosities of Olbyeossal(70 B.U., 50 B.U.) and WBR(10 B.U., 30 B.U.) were lower than those of DCR(120 B.U., 275 B.U.) and GBR(142 B.U., 340 B.U.).

• Food Science and Preservation
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• v.23 no.7
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• pp.953-959
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• 2016

The quality characteristics and processing of rice cake (Backsulgi) with rice flour containing Lactobacillus plantarum CGKW3 by spray-drying (LP-B) were investigated. The LP-B was applied at ratios of 10, 20, and 30 (w/w), and the moisture contents and pH were 33.39%~36.70% and 5.81~5.46, respectively. The L value of LP-B increased as the rice flour decreased, while the a and b value increased as the LP-B increased. The texture profiles showed that Backsulgi prepared with LP-B mixture had higher hardness, cohesiveness, springiness and chewiness than 100% rice flour. The pH of LP-B Backsulgi (LP-B20 and LP-B30) did not differ during 6 days at room temperature. The total bacteria in Backsulgi prepared LP-B20 and LP-B30 Backsulgi was $10^4CFU/g$ after 2 days of storage at room temperature. The shelf life of Backsulgi prepared with LP-B20 and LP-B30 were extended by about 2 days when compared with the control at room temperature. Sensory evaluation showed that Backsulgi without LP-B20 had higher scores in terms of appearance, color, flavor, taste, texture, hardness and overall acceptability than Backsulgi without 100% rice flour. In conclusion, the results demonstrate that LP-B20 may prove quite useful as a Backsulgi flour with desirable properties.

• Food Science and Preservation
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• v.24 no.1
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• pp.1-7
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• 2017

This study was conducted to investigate the effects of egg shell calcium treatments on short-term storage of cut Kimchi cabbage. Egg shell ash powder (ESP-2) had the greatest calcium contents. Calcium solubility was greater in citric acid than acetic acid and ascorbic acid. Cut Kimchi cabbages ($3{\times}3cm$) were treated with 0.5%, 1.0%, and 2.0% egg shell powder (ESP-1), and egg shell ash powder (ESP-2), and 0.5% citric acid, put inside polyethylene (PE) bags, and stored at $5^{\circ}C$ for 6 weeks. Weight loss was about 99.85-99.90%, and the ratio was the lowest upon 0.5% ESP-2 treatment (p<0.05). The reduction ratios of soluble solids were 21.3-43.4%, and decreased in the order of 1.0% ESP-2 treatment and 0.5% ESP-1. The $L^*$ values decreased, whereas $a^*$ and $b^*$ values of Hunter colorimetry increased in all treatments. ${\Delta}E$ values were lowest upon 0.5% ESP-2 treatment. 0.5% ESP-2 treatment showed better quality characteristics than other treatments. Thus, egg shell calcium treatments could effectively enhance the shelf-life of cut Kimchi cabbage.

• Korean Journal of Food Science and Technology
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• v.37 no.4
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• pp.678-684
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• 2005

Extraction conditions, spectrometric, and sensory properties of pigment extracts from green discolored garlic (GDG) were studied for development of green index to evaluate degree of green discoloration of garlic. GDG pigments were extracted using polar solvents, such as methanol, ethanol, and water. Methanol with 1% HCl resulted in highest extraction of green pigments. Extraction of pigments was affected by temperature, and extracted pigments were partially destroyed at high temperatures. Optimum conditions for extraction of green pigments were $20^{\circ}C$ for 30 min. Because green pigments are unstable at room temperature, and no method has been reported to evaluate degree of green discoloration of garlic, color chart was designed by mixing varying amounts of control and GDG. High correlation was observed between sensory scores and "a" value of color chart samples (y=-3.465x - 11.676) with $R^2$ of 0.993. Green index (GI) was developed based on linear regression equation between sensory scores and "a" values. Sensory panel recognized green discoloration of garlic at $GI{\geq}3.0$. GI developed in this study could be utilized to evaluate degree of green discoloration of garlic during cold storage and distribution of garlic.

• Korean Journal of Food Science and Technology
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• v.35 no.4
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• pp.671-679
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• 2003

Effects of sun-dried, refined, seaweed, and bamboo salts on the quality of kochujang were studied by measuring enzymatic, microbial, and physicochemical characteristics of kochujang during 12 weeks of fermentation. Yeast count was low in the bamboo-salt kochujang, whereas that of aerobic bacteria was low in the seaweed-salt kochujang. Acid protease activity was high in the bamboo-salt kochujang, whereas amylase activity did not show any remarkable difference. Color change was lowest in the bamboo-salt kochujang. Water activities of all kochujangs decreased during fermentation with the lowest shown in the refined-salt kochujang. Consistency of seaweed-salt kochujang was the highest. Total sugar content was higher, whereas ORP was lower in the seaweed- and bamboo-salt kochujangs. Titratable acidity changed slightly in the bamboo-salt kochujang. Reducing sugar content was the lowest, whereas ethanol content was the highest in the refined-salt kochujang. Amino and ammonia nitrogen contents of kochujangs increased up to the middle of fermentation period then decreased with lower changes observed in the sun-dried and refined-salt kochujangs. Results of sensory evaluation indicated that the bamboo-salt kochujang was more acceptable than the sun-dried salt kochujang in taste, color, and overall acceptabilities.