• Food Science and Preservation
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• v.19 no.4
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• pp.470-476
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• 2012

Enzymatic action and microbial growth degrade the quality of fresh-cut lettuce. Browning, a bad smell, and softening during storage are the major forms of quality deterioration. Health-oriented consumers tend to avoid foods treated with chemicals to maintain their freshness. This study was conducted to evaluate the change in the quality of fresh-cut lettuce with combined low-temperature blanching (LB) and ultrasonication (US). The optimum condition was selected using the response surface methodology (RSM), through a regression analysis with the following independent variables; the ultrasonication time (X1), blanching temperature (X2), blanching time (X3), and dependent variable; ${\Delta}E$ value (y). It was found that the condition with the lowest ${\Delta}E$ value occurred with combined 90s US and $45^{\circ}C$ 90s LB (US+LB). The combined treatment group (US+LB) was stored at $10^{\circ}C$ for 9 days with the control group and each single-treatment group, with low-temperature blanching and ultrasonication. Overall, the US+LB group had a significantly high $L^*$ value, which indicates significantly low $a^*$, $b^*$, ${\Delta}E$, browning index, PPO, and POD activity values, and a low total bacteria count (p < 0.05). The US+LB group also had the highest sensory score (except for aroma and texture; p > 0.05).

• Food Science and Preservation
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• v.12 no.6
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• pp.522-528
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• 2005

Effects of packaging and storage temperature on the quality and shelf life of mungbean sprouts(vigna radiata (L.) Wilczek) were studied Mungbean sprouts were packaged in polypropylene films(PP) and oriented polypropylene films(OPP) with 200 g, 250 g, and 300 g and stored at $4^{\circ}C,\;8^{\circ}C$ and $12^{\circ}C$, respectively. The deterioration of quality of mungbean sprouts during storage was caused by wilting of hypocotyl, abscission of cotyledon and softening of tissue. Total weight loss never exceeded $1\%$ and no visible signs of shrivelling of mungbean sprouts were observed. At $4^{\circ}C,\;30{\mu}m$ of OPP film per 250 g mungbean sprouts provided the optimal atmosphere composition(i.e. $3\%\;\O_2\;and\;5\%\;CO_2$). A shelf life of 6 days was achieved with these conditions. Hardness of hypocotyl, when deterioration in freshness began, was about 1,027.2 g when considerably deteriorated Hunter b value was 13 in deteriorated hypocotyl, vs. 11 for hypocotyl of fresh mungbean sprouts was accelerated by fluctuating storage temperature by the increment of storage time. It also was found that the optimum shelf life period was estimated to be 6, 2 and 2 days for 4, 8 and $12^{\circ}C$, respectively.

• Journal of the Korea Concrete Institute
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• v.22 no.6
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• pp.851-858
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• 2010

In this study, waste glass and bottom ash were used as basic materials in order to secure a recycling technology of by-products which was mostly discarded and reclaimed. In addition, because softening point of waste glass is less than $700^{\circ}C$ and bottom ash includes combustible material, it was possible to manufacture low-temperature sintering lightweight aggregates for energy saving at $800{\sim}900^{\circ}C$ that it is as much as 20~30% lower than sintering temperature of existing lightweight aggregates. Thermal conductivity of newly-developed lightweight aggregates was 0.056~0.105W/m. K and its porosity was 40.36~84.89%. A coefficient of correlation between thermal conductivity and porosity was -0.97, it showed very high negative correlationship. With this, we were able to verify that porosity is key factor to affect thermal conductivity. Microstructure of lightweight aggregates by $CaCO_3$ content and replacement ratio of bottom ash in the variation of temperature were that $CaCO_3$ content increased along with pore size while replacement ratio of bottom ash increased as pore size decreased. Specially, most pores were open pore instead of closed pore of globular shape when replacement ratio of bottom ash was 30%, and pore size was small about 1/10~1/5 as compared with case in bottom ash 0~20%. In addition, open pore shapes were remarkably more irregular form of open pore in $900^{\circ}C$ than $700^{\circ}C$ or $800^{\circ}C$ when replacement ratio of bottom ash was 30%. We reasoned hereby that these results will influence on absorption increase, strength and thermal conductivity decrease of lightweight aggregates.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.8
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• pp.1141-1149
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• 2011

The objective of this study was to analyze quality changes during storage of fresh-cut produce (leafy vegetables and condiment vegetables) as a function of packaging and storage temperature. Fresh-cut produce was washed using a three step cleaning process and was packed in vacuum packaging (green onion, hot pepper, onion, baechu) and perforated film packaging (buchu and perilla leaf). The effects of packaging method and storage temperature on quality of fresh-cut produce were determined by analyzing total plate counts, E. coli, coliform groups, moisture content, pH, Aw, surface color, and exterior quality during storage at 4 and 10$^{\circ}C$. According to the results, surface color change and microbial growth were delayed during storage at 4$^{\circ}C$. Additionally, E. coli was not detected during storage. Generally, moisture content decreased in the perforated film packaging. Changes in surface quality such as skin browning, softening of tissue and chlorosis at 4$^{\circ}C$ were inhibited, whereas rapid vacuum annealing and changes in color and flavor were observed in the sample stored at 10$^{\circ}C$. The result indicated that overall quality of the fresh-cut produce at 4$^{\circ}C$ was well maintained. The perforation in packing materials did not significantly increase the number of microorganisms on buchu and perilla leaf. The proper packaging methods and temperature may beneficial effect on microbial safety, quality and thus result in longer shelf-life fresh-cut vegetables during distribution.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.4
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• pp.315-321
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• 2003

The integrity of the turbine rotors can be assessed by measuring the material properties at service temperature. In order to evaluate the remanent life of turbine rotor steel nondestructively, a measurement system of reversible magnetic permeability using an alternating perturbing magnetic field was constructed. We present a new non-destructive method to evaluate the remanent life of 1Cr-1Mo-0.25V steel using the value of reversible magnetic permeability. This method is based on the existence of reversible magnetic permeability in the differential magnetization around the coercive field strength. We measured the first harmonics voltage induced in a coil using a lock-in amplifier tuned to an exciting frequency. The Results of reversible magnetic Permeability and Wickers hardness on the aged samples show that the peak interval of reversible magnetic permeability (PIRMP) and Vickers hardness decreases as aging time increases. A softening curve is obtained from the correlation between Vickers hardness and the PIRMP. This curve can be used as a non-destructive method to evaluate the remanent life of turbine rotor steel.

• Applied Biological Chemistry
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• v.46 no.1
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• pp.39-45
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• 2003

This study was conducted to investigate the effect of ash contents of bread flour on the rheology of frozen dough In making frozen dough by measuring amylograph, flrinograph and extensograph. The quality of frozen-stored dough under freezing condition ($-20^{\circ}C$, 12 weeks) was evaluated by measuring final proof time, moisture content, baking loss, loaf volume and hardness of bread with storage time. In bread flour with high ash content farinogram showed that water absorption, degree of softening increased but valorimeter value decreased. In bread flour with low ash content amylogram showed that gelatinization temperature and maximum viscosity increased and extensogram showed that the area and resistance of the bread flour increased. As the proof time increased the extensibility decreased. Final proof time of frozen dough was shortened at the bread flour with low ash content with storage time. In bread using the flour with high ash content, moisture content, increased but baking loss rate decreased while the hardness of product increased slowly with time. But in bread using the flour with low ash content, the loaf volume of baking increased but the hardness of product decreased. As the frozen storage time was shortened, the product was more stable and better in quality.

• Microbiology and Biotechnology Letters
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• v.33 no.4
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• pp.248-254
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• 2005

One hundred thirty nine bacteria were isolated from rotten onions collected from main producing districts, Chang-Nyung, Eui-Ryung, and Ham-Yang in Korea. The $18\%$ (25 strains) of bacterial isolates have carboxymethylcellulase (CMCase) activity and the $53\%$ (74 strains) have polygalacturonase (PGase) activity. Thirty one among randomly selected 45 strains of PGase producing bacteria have pathogenicity to onions. The isolates were classified into Pseudomonas sp. (18 strains), Bacillus sp. (11 strains), Yers-inia sp. (7 strains), and others (9 strains) on the basis of FAMEs patterns. Eighteen strains of Pseudomonas sp. were mainly divided into three cluster in the dendrogram and only the two clusters of them showed pathogenicity to onions. CMCase and PGase activities of Pseudomonas sp. weaker than those of Bacillus sp.. However, the pathogenicity of pseudomonas sp. to soften onions was stronger than that of Bacillus sp. Inoculation of $10^{2}$ cfu of Pseudomonas sp. gives rise to softening of onions. Pseudomonas sp. was identified as Pseudomonas gladioli by biochemical and physiological characteristics. P. gladioli is the first reported bacterium as a pathogen of onion in Korea. In low temperature, P. gladioli showed better growth and higher PGase activity than those of Bacillus sp. identified as Bacillus subtilis. And pH 9.0 is optimal pH for PGase activity of B. subtilis while that of P. gladioli is pH $5.0\∼6.0$ which is the acidity of onions. Taken together, P. gladioli may be a main pathogene of onion rot during the cold storage condition.

• Korean Journal of Food Science and Technology
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• v.18 no.2
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• pp.130-136
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• 1986

'Shingo' pears were seal-packaged in polyethylene (PE) film with different thickness of 0.04. 0.06, 0.07, and 0.08mm and stored for five months in an experimental storehouse with the temperature varyine 0 to $7^{\circ}C$ and relative humidity varying 86 to 89%. The atmosphere in PE film bags was modified to 5-l4% oxygen with 3-5% carbon dioxide depending on the film thickness and the storage period. Packaging of pears with PE film effectively reduced the weight loss, which resulted in good appearance after 5 months' storage, while non-packaged pears showed a slight wilt. Decay occurrence was not significantly different among the treatments. but role browning occurred a little more in packaged lots than in non-packaged lot. The sensory panel rated the pears front 0.07mm-thick bag highest in flavor, texture, and juiciness, which might be due to the high sugar content and low titratable acidity. The firmness of pear flesh decreased with the stogare time and its change was found to be highly correlated with that of cellulase activity (correlation coefficient= -0.946). Thisresult indicated that cellulase might be one of the enzymes responsible for the softening of pear fruit during storage.

• Journal of Applied Biological Chemistry
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• v.52 no.4
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• pp.157-162
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• 2009

An agar-liquefying bacteria (SC-22), which produces a diffusible agarase that caused agar softening around the colony was isolated from Daecheong lake in Korea. Chemotaxanomic and phylogenetic analyses based on 16S rRNA gene sequences revealed the strain was classified as Cellvibrio mixtus SC-22. The isolate SC-22 showed maximal extracellular agarase activity with 58.5 U/mL after 48 h cultivation in the presence of 0.2% agar. It was observed that the isolate produced two kinds of extracellular and three kinds of intracellular isoenzymes. The major agarase was purified from the culture filtrate of agarolytic bacteria by ammonium sulfate precipitation, anion exchange and gel filtration column chromatographic methods. The molecular mass of the purified enzyme was estimated to be 25 kDa by SDS-PAGE. The optimum pH and temperature of the purified enzyme were pH 7.0 and $50^{\circ}C$, respectively. The agarase activity was activated by $Fe^{2+}$, $Na^+$ and $Ca^{2+}$ ions while it was inhibited by $Hg^{2+}$, $Mn^{2+}$ and $Cu^{2+}$ at 1 mM concentration. The predominant hydrolysis product of agarose by the enzyme was galactose and disaccharide on TLC, indicating the cleavage of $\beta$-1,4 linkage in a random manner. The enzyme showed high substrate specificity for only agar and agarose among various polysaccharides.

• Journal of Mushroom
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• v.16 no.3
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• pp.131-139
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• 2018

The king oyster mushroom (Pleurotus eryngii) is widely consumed because of its flavor, texture, and its functional properties such as antioxidant activity and prebiotic effects. However, long-term product storage and transportation (e.g., export) are difficult because of its limited durability. The shelf-life of king oyster mushroom is affected by environmental factors such as temperature, humidity, gas composition, and ventilation, which may affect sensory characteristics including respiration rate, texture, moisture, flavor, color, and pH. The major problems regarding storage of mushrooms are browning, flavor changes, and softening. To address these problems, novel preservation techniques were developed, and more durable variants were bred. Different drying methods, gamma irradiation, chitosan coating, modified atmosphere (MA) packaging, and controlled atmosphere (CA) storage were evaluated in order to extend the shelf-life of king oyster mushrooms. Freeze drying showed better results for the preservation of mushrooms than other drying methods. Irradiation with 1 kGy was more effective for extending mushroom shelf-life than higher doses. The preservative performance of chitosan-based films was improved by combining the compound with other hydrocolloids, such as oil, protocatechuic acid, and wax. The CA storage conditions recommended for king oyster mushrooms are 5kPa $O_2$ and 10 to 15kPa $CO_2$ at temperatures below $10^{\circ}C$. Active MA packaging with microperforated PP film was also effective for maintaining quality during storage.