• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.33-39
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• 2021

As the interest and demand in the recycled yarn field has increased rapidly worldwide, domestic companies are also promoting research and development and business on recycled yarn. The chemical and thermal properties of four types of virgin and recycled PET samples from A and B company, which are the leading domestic companies in the recycled polyester yarn business, were confirmed through infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC). Virgin and recycled PET from two companies were compared. FT-IR spectroscopy revealed the typical spectra of PET for both companies and a different peak at 872 cm-1. DSC confirmed that the melting point and crystallization temperature of recycled PET were lower than those of virgin PET. These results indicate that small amounts of contaminants are an important parameter affecting the thermal properties of recycled PET. In the DSC results after seven repeats of the heating and cooling processes, all four samples showed that a lower melting point, crystallization temperature, and low heat flow intensity increased with increasing number of cycles. The results of melting and crystallization enthalpy also showed similar patterns.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.323-332
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• 2021

This study was undertaken to develop a new combination tablet containing silodosin and solifenacin succinate for treating urination disorders, for which a simultaneous analytical method of silodosin and solifenacin succinate was established. The aqueous solubility of silodosin and solifenacin succinate was determined to be higher than 1 mg/ml in various buffers, and dissolution of the silodosin and solifenacin succinate commercial products was accomplished within 30 minutes. The drug-excipients compatibility test was subsequently evaluated using differential scanning calorimetry. Excipients without compatibility were selected, and various combination formulations were prepared applying the wet granulation method. Of these, the formulation comprising silodosin, solifenacin succinate, lactose hydrate, MCC PH101, sodium lauryl sulfate (SLS), Povidone K30, crospovidone and magnesium stearate, having a weight ratio of 8/10/56/112/2/6/6/2, respectively, showed equivalence comparative to the dissolution achieved with the commercial products of silodosin (Thrupas tab) and solifenacin succinate (Vesicare tab). Thus, we propose that compared to the currently available commercial products, this novel combination tablet containing silodosin and solifenacin succinate is an effective alternative for the treatment of urination disorders.

• Applied Chemistry for Engineering
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• v.33 no.4
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• pp.386-393
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• 2022

In this study, the surface modification of calcium carbonate (CaCO₃) nanoparticles by a silane coupling agent, octyltrimethoxysilane (OTMS), was investigated and characterized using Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) analysis. Both floating tests and contact angle measurements were also conducted to study the effect of OTMS concentration on the hydrophobicity of CaCO₃ nanoparticles. It was found that the active ratio for the CaCO₃ nanoparticles modified by 1 wt% of OTMS was 97.0 ± 0.5%, indicating that OTMS is a very effective silane coupling agent in enhancing the hydrophobicity of the CaCO₃ nanoparticle surface. The most stable foam was generated with 1 wt% of CaCO₃ nanoparticles in aqueous solutions at 1 wt% of OTMS, where the contact angle of water was found to be 91.8 ± 0.7°. It was also found that the most stable emulsion drops were formed at the same OTMS concentration. These results suggest that CaCO₃ nanoparticles modified by a silane coupling agent OTMS are a powerful candidate for a foam stabilizer or an emulsifier in many industrial applications.

• Resources Recycling
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• v.31 no.6
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• pp.52-59
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• 2022

Calcium silicate based cement (CSC) is a low-carbon cement that emits less CO₂ by up to 70% compared to ordinary Portland cement during its manufacture. Most developed countries have commercialized CSC, whereas Korea is still investigating the manufacturing characteristics and basic properties of CSC. This paper provides a review of methods for manufacturing CSC using domestic raw materials and discusses the possibility of CSC localization based on an evaluation of the basic physical properties of manufactured CSC. The experimental results of this study indicate that the primary mineral components of CSC were CS, C₃S₂ C₂S, and unreacted SiO₂. This suggests the possibility of manufacturing CSC using domestic raw materials that exhibit mineral compositions similar to that of theoretical CSC. The compressive strength of CSC mortar is less than 1MPa at the age of 7 d under wet curing. This implies that hydration does not affect the property development of CSC mortar. Meanwhile, during carbonation curing, the compressive strength is 56 MPa or higher after 7 d, which indicates excellent early strength development. Furthermore, results of Thermogravimetric Analysis Differential scanning calorimetry (TG/DSC) show that a significant amount of CaCO₃ is formed, which is consistent with the results of previous studies. This implies that carbonation is associated significantly with the properties of CSC.

• Composites Research
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• v.36 no.2
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• pp.126-131
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• 2023

Growing environmental concerns regarding pollution caused by conventional plastics have increased interest in biodegradable polymers as alternative materials. The purpose of this study is to develop a 100% biodegradable nanocomposite material by introducing organic nucleating agents into the biodegradable and thermoplastic resin, poly(lactic acid), to improve its properties. Accordingly, cellulose nanofibers, an eco-friendly material, were adopted as a substitute for inorganic nucleating agents. To achieve a uniform dispersion of cellulose nanofibers (CNFs) within PLA, the aqueous solution of nanofibers was lyophilized to maintain their fibrous shape. Then, they were subjected to primary mixing using a twin-screw extruder. Test specimens with double mixing were then produced by injection molding. Differential scanning calorimetry was employed to confirm the reinforced physical properties, and it was found that the addition of 1 wt% CNFs acted as a reinforcing material and nucleating agent, reducing the cold crystallization temperature by approximately 14℃ and increasing the degree of crystallization. This study provides an environmentally friendly alternative for developing plastic materials with enhanced properties, which can contribute to a sustainable future without consuming inorganic nucleating agents. It serves as a basis for developing 100% biodegradable green nanocomposites.

• Journal of the Korean Society of Food Culture
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• v.24 no.1
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• pp.69-76
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• 2009

This study was conducted to determine the optimal cooking conditions for brown rice using an electric pressure rice cooker. The effects of steeping conditions and cooking pressure on the hydration, gelatinization, texture and palatable properties of cooked brown rice were evaluated. Based on water uptake and DSC data, the optimal steeping time and temperature for brown rice were determined to be 25 minutes and ${\sim}60^{\circ}C$, respectively. The cooking conditions for brown rice were then divided into the following 6 categories: steeping at $25^{\circ}C$ for 25 minutes and cooking at an atmospheric pressure of 1.7 (25P) or 1.9 (25HP), steeping at $57^{\circ}C$ for 25 minutes and cooking at an atmospheric pressure of 1.7 (57P) or 1.9 (57HP), steeping at $85^{\circ}C$ for 15 minutes and cooking at an atmospheric pressure of 1.7 (85P) or 1.9 (85HP). The susceptibility of cooked brown rice starch to degradation into maltose by ${\alpha}$-amylase, which is related to the degree of gelatinization and in vitro digestibility, were then determined. The amount of maltose produced by cooked brown rice samples was highest in the 57HP group, followed by the 57P and 85HP groups. Storing cooked brown rice at $73^{\circ}C$ for 24 hours resulted in significantly higher amounts of starch being degraded into maltose in the 57P, 57HP and 85HP groups than in the other groups. Textural analysis demonstrated that the 57P, 57HP and 85HP groups had significantly lower gumminess and chewiness values when compared to the other groups, and that 57HP received had the lowest hardness of all treatments. These results were confirmed by the results of the sensory evaluations. Furthermore, the 57P and 57HP groups were found to have a higher glossiness, stickiness aroma and taste score than the other groups. These findings were taken to indicate that steeping conditions and pressure exerted a positive synergistic effect on the cooking quality of brown rice. The texture analyzer also revealed that storing the cooked rice at $73^{\circ}C$ for 24 hours only led to significantly lower scores in gumminess, hardness and chewiness in the 57P and 57HP groups, which indicates that these groups underwent a lesser degree of retrogradation than other groups. Taken together, the results of the present study demonstrate that steeping brown rice at $57^{\circ}C$ for 25 minutes and a higher cooking pressure improved the palatability and in vitro digestibility of brown rice significantly.

• Korean Journal of Food Science and Technology
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• v.37 no.6
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• pp.873-881
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• 2005

This study was conducted to improve the properties of frozen dough foods (buns and noodles etc.) on the quality deterioration with microwave oven cooking. Microwave is a useful cooking method, but it quickly takes moisture from food surface and makes lowering food quality abruptly. For improvement of these problems, mixing doughs with addition of various additives of 34 types manufactured respectively; starches, modified starches, gums and emulsifiers etc. Each mixing dough produced in sheet type $(30{\times}30{\times}1mm)$ and steamed them, was quickly froze at $-70^{\circ}C$ and packed with polyethylene. Packed samples kept at $-20^{\circ}C$ for 48 hours. After they were steam or microwave treatment packed or non-packed with polyethylene, studied for improvement effects of quality as sensory evaluation and selected 6 type additives; modified starches (TA, ST), gums (AR, GA) and emulsifiers (E, S1) as improvement agent. Because moisture loss from microwave oven cooking leads to quality deterioration of frozen dough foods, additive, such as including starches, modified starch, gums, and emusifiers were added to improve dough properties. Amylogram, scanning electron microscopy, textural analysis, and differential scanning calorimetry revealed addition of additives improved textural properties including surface-hardening of frozen dough foods compared to the control.

• 한국유가공학회:학술대회논문집
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• 2002.04a
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• pp.59-60
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• 2002

Edible films such as wax coatings, sugar and chocolate covers, and sausage casings, have been used in food applications for years$^{(1)}$ However, interest in edible films and biodegradable polymers has been renewed due to concerns about the environment, a need to reduce the quantity of disposable packaging, and demand by the consumer for higher quality food products. Edible films can function as secondary packaging materials to enhance food quality and reduce the amount of traditional packaging needed. For example, edible films can serve to enhance food quality by acting as moisture and gas barriers, thus, providing protection to a food product after the primary packaging is opened. Edible films are not meant to replace synthetic packaging materials; instead, they provide the potential as food packagings where traditional synthetic or biodegradable plastics cannot function. For instance, edible films can be used as convenient soluble pouches containing single-servings for products such as instant noodles and soup/seasoning combination. In the food industry, they can be used as ingredient delivery systems for delivering pre-measured ingredients during processing. Edible films also can provide the food processors with a variety of new opportunities for product development and processing. Depends on materials of edible films, they also can be sources of nutritional supplements. Especially, whey proteins have excellent amino acid balance while some edible films resources lack adequate amount of certain amino acids, for example, soy protein is low in methionine and wheat flour is low in lysine$^{(2)}$. Whey proteins have a surplus of the essential amino acid lysine, threonine, methionine and isoleucine. Thus, the idea of using whey protein-based films to individually pack cereal products, which often deficient in these amino acids, become very attractive$^{(3)}$. Whey is a by-product of cheese manufacturing and much of annual production is not utilized$^{(4)}$. Development of edible films from whey protein is one of the ways to recover whey from dairy industry waste. Whey proteins as raw materials of film production can be obtained at inexpensive cost. I hypothesize that it is possible to make whey protein-based edible films with improved moisture barrier properties without significantly altering other properties by producing whey protein/lipid emulsion films and these films will be suitable far food applications. The fellowing are the specific otjectives of this research: 1. Develop whey protein/lipid emulsion edible films and determine their microstructures, barrier (moisture and oxygen) and mechanical (tensile strength and elongation) properties. 2. Study the nature of interactions involved in the formation and stability of the films. 3. Investigate thermal properties, heat sealability, and sealing properties of the films. 4. Demonstrate suitability of their application in foods as packaging materials. Methodologies were developed to produce edible films from whey protein isolate (WPI) and concentrate (WPC), and film-forming procedure was optimized. Lipids, butter fat (BF) and candelilla wax (CW), were added into film-forming solutions to produce whey protein/lipid emulsion edible films. Significant reduction in water vapor and oxygen permeabilities of the films could be achieved upon addition of BF and CW. Mechanical properties were also influenced by the lipid type. Microstructures of the films accounted for the differences in their barrier and mechanical properties. Studies with bond-dissociating agents indicated that disulfide and hydrogen bonds, cooperatively, were the primary forces involved in the formation and stability of whey protein/lipid emulsion films. Contribution of hydrophobic interactions was secondary. Thermal properties of the films were studied using differential scanning calorimetry, and the results were used to optimize heat-sealing conditions for the films. Electron spectroscopy for chemical analysis (ESCA) was used to study the nature of the interfacial interaction of sealed films. All films were heat sealable and showed good seal strengths while the plasticizer type influenced optimum heat-sealing temperatures of the films, 130$^{\circ}$C for sorbitol-plasticized WPI films and 110$^{\circ}$C for glycerol-plasticized WPI films. ESCA spectra showed that the main interactions responsible for the heat-sealed joint of whey protein-based edible films were hydrogen bonds and covalent bonds involving C-0-H and N-C components. Finally, solubility in water, moisture contents, moisture sorption isotherms and sensory attributes (using a trained sensory panel) of the films were determined. Solubility was influenced primarily by the plasticizer in the films, and the higher the plasticizer content, the greater was the solubility of the films in water. Moisture contents of the films showed a strong relationship with moisture sorption isotherm properties of the films. Lower moisture content of the films resulted in lower equilibrium moisture contents at all aw levels. Sensory evaluation of the films revealed that no distinctive odor existed in WPI films. All films tested showed slight sweetness and adhesiveness. Films with lipids were scored as being opaque while films without lipids were scored to be clear. Whey protein/lipid emulsion edible films may be suitable for packaging of powder mix and should be suitable for packaging of non-hygroscopic foods$^{(5,6,7,8,)}$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.3
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• pp.366-372
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• 2006

This study is to investigate the physicochemical properties of differently pretreated chestnut starches during starch isolation and to examine their gelatinization properties by both heat and alkali treatments. One kind is starch A made by alkali method from peeled chestnut. The other is starch B made from chestnut with the outer layer. The results are as follows. Starch A has higher water binding capacity of 86.9% than starch B with 80.66%. Swelling powers of both starch A and B increased rapidly from $60^{\circ}C\;to\;80^{\circ}C$ in both, and since then it has changed a bit. Both began to show their solubility at $60^{\circ}C$ and increased continuously as the temperature went up. Starch A has higher swelling power and solubility than starch B. In iodine reaction, starch A has higher ${\lambda}max$ and absorbance at ${\lambda}max$ than starch B. X-ray diffraction patterns showed that starch A is type $C_b$ and that starch B is type B. Starch B has higher relative crystallinity of 37.0% than starch A with 36.2%. The results by differential scanning calorimetry revealed that starch A gelatinized from $66.95^{\circ}C$ to $77.5^{\circ}C$ and its enthalpy is 2.04 cal/g. And starch B gelatinized from $67.09^{\circ}C\;to\;77.5^{\circ}C$, and its enthalpy is 2.29 cal/g. Amylograms of chestnut starch at 6.5% concentration indicated that starch B needs higher onset temperature when beginning to gelatinize than starch A does. But starch A shows much higher peak viscosity, breakdown and setback than starch B does. Starch A shows higher viscosity, gel volume, and optical transmittance in gelatinization properties by alkali than starch B does.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2005.06a
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• pp.154-164
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• 2005

Saccharomyces cerevisiae KNU5377 is a thermotolerant strain, which can ferment ethanol from wasted papers and starch at 40$^{\circ}C$ with the almost same rate as at 30$^{\circ}C$. This strain showed alcohol fermentation ability to convert wasted papers 200 g (w/v) to ethanol 8.4% (v/v) at 40$^{\circ}C$, meaning that 8.4% ethanol is acceptable enough to ferment in the industrial economy. As well, all kinds of starch that are using in the industry were converted into ethanol at 40$^{\circ}C$ with the almost same rate as at 30$^{\circ}C$. Hyperthermic cell killing kinetics and differential scanning calorimetry (DSC) revealed that exponentially growing cells of this yeast strain KNU5377 were more thermotolerant than those of S. cerevisiae ATCC24858 used as a control. This intrinsic thermotolernace did not result from the stability of entire cellular components but possibly from that of a particular target. Heat shock induced similar results in whole cell DSC profiles of both strains and the accumulation of trehalose in the cells of both strains, but the trehalose contents in the strain KNU5377 were 2.6 fold higher than that in the control strain. On the contrary to the trehalose level, the neutral trehalase activity in the KNU5377 cells was not changed after the heat shock. This result made a conclusion that though the trehalose may stabilize cellular components, the surplus of trehalose in KNU5377 strain was not essential for stabilization of whole cellular components. A constitutively thermotolerant yeast, S. cerevisiae KNU5377, was compared with a relatively thermosensitive control, S. cerevisiae ATCC24858, by assaying the fluidity and proton ATPase on the plasma membrane. Anisotropic values (r) of both strains were slightly increased by elevating the incubation temperatures from 25$^{\circ}C$ to 37$^{\circ}C$ when they were aerobically cultured for 12 hours in the YPD media, implying the membrane fluidity was decreased. While the temperature was elevated up to 40$^{\circ}C$, the fluidity was not changed in the KNU5377 cell, but rather increased in the control. This result implies that the plasma membrane of the KNU5377 cell can be characterized into the more stabilized state than control. Besides, heat shock decreased the fluidity in the control strain, but not in the KNU5377 strain. This means also there's a stabilization of the plasma membrane in the KNU5377 cell. Furthermore, the proton ATPase assay indicated the KNU5377 cell kept a relatively more stabilized glucose metabolism at high temperature than the control cell. Therefore, the results were concluded that the stabilization of plasma membrane and growth at high temperature for the KNU5377 cell. Genome wide transcription analysis showed that the heat shock responses were very complex and combinatory in the KNU5377 cell. Induced by the heat shock, a number of genes were related with the ubiquitin mediated proteolysis, metallothionein (prevent ROS production from copper), hsp27 (88-fold induced remarkably, preventing the protein aggregation and denaturation), oxidative stress response (to remove the hydrogen peroxide), and etc.