• Journal of Korean Society of Environmental Engineers
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• v.32 no.4
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• pp.341-348
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• 2010

The basic principle of fry drying process of sludge lies in the rapid pressure change of sludge material caused by the change of temperature between oil and moisture due to the difference of specific heat. Therefore, the rapid increase of pressure in drying sludge induces the efficient moisture escape through sludge pores toward heating oil media. The object of this study is to carry out a systematic investigation of the influence of various parameters associated with the sludge fry drying processes on the drying efficiency. To this end, a series of parametric experimental investigation has been made together with the numerical calculation in order to obtain typical drying curves as function of important parameters such as drying temperature, sludge diameter, oil type and sludge type. In the aspect of frying temperature, especially it is found that the operation higher than $140^{\circ}C$ was favorable in drying efficiency regardless of type of waste oil employed in this study. The same result was also noted consistently in the investigation of numerical calculation, that is, in that the sludge particle drying was efficiently made over $140^{\circ}C$ irrespective of the change of particle diameter. As expected, in general, the decrease of diameter in sludge was found efficient both experiment and numerical calculation in drying due to the increased surface area per unit volume. In the investigation of oil type and property, the effect of the viscosity of waste oil was found to be more influential in drying performance. In particular, when the oil with high viscosity, a visible time delay was noticed in moisture evaporation especially in the early stage of drying. However, the effect of high viscosity decreased significantly over the temperature of $140^{\circ}C$. There was no visible difference observed in the study of sludge type but the sewage sludge with a slightly better efficiency. The numerical study is considered to be a quite useful tool to assist in experiment with more detailed empirical modeling as further work.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.8
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• pp.1248-1256
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• 2014

The purpose of this study was to investigate the mechanisms of behind $SO_2$ formation and elevated cause of reducing power in purple bamboo salt (PBS) along with an analysis of physicochemical properties, content of sulfur compounds, oxidation reduction potential (ORP), mineral contents of salt type (MSS, mudflat solar salt; BS, bamboo salt), and addition of raw bamboo (RB). $SO_2$ content of 630 ppm was detected in PBS. $SO_2$ was not detected in MSS, BS, or RB, whereas $SO_2$ (782 ppm) from $K_2SO_4$ was detected after heating a NaCl, KCl, $MgCl_2$, $MgSO_4$, MgO, $CaCl_2$, $K_2SO_4$, and $FeSO_4$ with RB. $SO_2$ content of BS increased with baking time, and it originated from BSRB1 (13.88 ppm) to BSRB4 (109.13 ppm). $SO_3{^{2-}}$ originated only from MSSRB4 and BSRB2~BSRB4. Sulfate ion content decreased along with increasing $SO_2$ and sulfite ion contents. ORP increased with baking time of MSS and BS, and it was present at higher levels in BSRB4 (-211.40 mV) of BS than MSS. Insoluble content was higher in BS than MSS. Further, Ca, K, and Mg ion contents decreased in MSS and increased in BS with baking time. BSRB4 had 1.4 fold higher levels of Ca, 1.5 fold higher levels of Mg, and 1.8 fold higher levels of K than BS. Li, Al, Mn, Fe, and Sr in MSS as well as Al, Fe, and Ni in BS increased with baking time. Anions (Cl, $NO_3$, and Br) and heavy metals (Pb, Cd, Hg, and As) between MSS and BS were not significantly different. These results suggest that the reducing power of BS was due to $SO_2$ and sulfite ion. To increase the amounts of these compounds and reducing power, higher melting temperature and longer baking time are necessary along with BS, which is created by the addition of RB to roasted salt.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.5
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• pp.361-372
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• 1990

Processing conditions of whole sardine into modified fish sauce were investigated. Thawed and chopped sardine was homogenized and hydrolyzed using commercial proteolytic enzymes such as complex enzyme-2000($2.18{\cdot}10^4U/g solid$) and alcalase($1.94{\cdot}10^4\;U/g solid$) in a cylindrical vessel with 4 baffles and 6-bladed impeller. Optimal pH, enzyme concentration and temperature for the hydrolysis with complex enzyme-2000 were 7.0, $7\%$ (W/W) and $52^{\circ}C$, and-those with alcalase were 8.0, $6\%$ (W/W) and $60^{\circ}C$. In both cases, the reasonable amount of water for homogenization, agitation speed and hydrolyzing time were $100\%$ (W/W), 100 rpm and 210 minutes. Thermal treatment of the filtered hydrolysate at $90^{\circ}C$ for 2 hours with $6\%$ of invert sugar was adequated to inactivation of the enzymes and pasteurization of the hydrolysate. Flavor, taste and color of the hydrolysate were improved during the heating process in which the browning products might participate. The content of free amino nitrogen in the fish sauce seasoned with $15\%$ of table salt was ca. $1,640 mg\%$. Yield of the fish sauce based on the contents of proteinous and free amino nitrogen in the raw whole sardine was ca. $86\%$, and ca. $96\%$ of these compounds of the fish sauce was in the form of free amino nitrogen. The pH, salinity and histamine content of the fish sauce were $6.1\~6.3,\;14.2\~14.3\%$ and less than $10\;mg\%$.

• Tunnel and Underground Space
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• v.33 no.3
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• pp.189-207
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• 2023

In the present study, the thermoshearing experiment on a rough rock fracture were modeled using a three-dimensional grain-based distinct element model (GBDEM). The experiment was conducted by the Korea Institute of Construction Technology to investigate the progressive shear failure of fracture under the influence of thermal stress in a critical stress state. The numerical model employs an assembly of multiple polyhedral grains and their interfaces to represent the rock sample, and calculates the coupled thermo-mechanical behavior of the grains (blocks) and the interfaces (contacts) using 3DEC, a DEM code. The primary focus was on simulating the temperature evolution, generation of thermal stress, and shear and normal displacements of the fracture. Two fracture models, namely the mated fracture model and the unmated fracture model, were constructed based on the degree of surface matedness, and their respective behaviors were compared and analyzed. By leveraging the advantage of the DEM, the contact area between the fracture surfaces was continuously monitored during the simulation, enabling an examination of its influence on shear behavior. The numerical results demonstrated distinct differences depending on the degree of the surface matedness at the initial stage. In the mated fracture model, where the surfaces were in almost full contact, the characteristic stages of peak stress and residual stress commonly observed in shear behavior of natural rock joints were reasonably replicated, despite exhibiting discrepancies with the experimental results. The analysis of contact area variation over time confirmed that our numerical model effectively simulated the abrupt normal dilation and shear slip, stress softening phenomenon, and transition to the residual state that occur during the peak stress stage. The unmated fracture model, which closely resembled the experimental specimen, showed qualitative agreement with the experimental observations, including heat transfer characteristics, the progressive shear failure process induced by heating, and the increase in thermal stress. However, there were some mismatches between the numerical and experimental results regarding the onset of fracture slip and the magnitudes of fracture stress and displacement. This research was conducted as part of DECOVALEX-2023 Task G, and we expect the numerical model to be enhanced through continued collaboration with other research teams and validated in further studies.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.2
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• pp.125-136
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• 1990

To develope a rapid processing method for fish sauce, processing conditions of fish sauce from sardine waste was investigated. The chopped waste was homogenized and hydrolyzed by commercial proteolytic enzymes such as Complex enzyme-2000($2.18\cdot10^4$ U/g solid) and Alcalase($1.94\cdot10^4$ U/g solid) in a cylindrical vessel with 4 baffles and 6-bladed turbine impeller. Optimal temperature for the case of hydrolysis with Complex enzyme-2000 was 50 and that with Alcalase was $55^{\circ}C$. In both cases, the reasonable pH, amount of water for homo-genization, enzyme concentration and hydrolyzing time were 8.0, $40\%$ (W/W), $3\%$ and 100 min, respectively. Heating of the filtrated hydrolysate for 2 hours at $90^{\circ}C$ with $6\%$ of invert sugar was suitable for pasteurization of the hydrolysate and inactivation of enzymes. Flavor, taste and color of the hydrolysate was improved during the thermal treatment in which the browning reaction products might participate and result in antioxidative and bactericidal effects. Combined use of $0.005\%$ of Caryophylli flos with invert sugar was also effective for the improvement of taste. Yield of the fish sauce based on the total nitrogen in the raw sardine waste was $91.2\~92.3\%$ and $87.2\~87.8\%$ of the total nitrogen in the fish sauce was in the form of amino nitrogen. The pH, salinity and histamine content of the fish sauce prepared with $15\%$ of table salt were $6.1\~6.2$, $14.2\~14.4\%$ and less than $10mg\%$, respectively. The fish sauce was stable during the storage of 60 days at $26\pm3^{\circ}C$ on bacterial growth and its quality was also maintained.

• Journal of the Korean Wood Science and Technology
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• v.49 no.3
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• pp.213-225
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• 2021

In this paper, we investigated the carbonization characteristics of lignin hydrochar prepared by hydrothermal carbonization and established a model for predicting the carbonization degree using near-infrared spectroscopy and partial least squares regression. The carbon content of the hydrothermally carbonized lignin at the temperature of 200 ℃ was higher by approximately 3 wt% than that of the untreated sample, and the carbon content tended to gradually increase as the heating time increased. Hydrothermal carbonization made lignin more carbon-intensive and more homogeneous by eliminating the microparticles. The discriminant and predictive models using near-infrared spectroscopy and partial least squares regression approppriately determined whether hydrothermal carbonization has been applied and predicted the carbon content of hydrothermal carbonized lignin with high accuracy. In this study, we confirmed that we can quickly and nondestructively predict the carbonization characteristics of lignin hydrochar manufactured by hydrothermal carbonization using a partial least squares regression model combined with near-infrared spectroscopy.

• The Korean Journal of Food And Nutrition
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• v.26 no.4
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• pp.857-864
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• 2013

This study was investigated the effects of heat treatment on polyphenolic compounds and antioxidant activities of yacon. Raw yacon was heated at $100^{\circ}C$ and $121^{\circ}C$ for 15, 30, or 60 min by using an autoclave. The browning intensity, levels of free and bound phenolic and flavonoid compounds, and 1,1-diphenyl-2-picrylhydrazyl(DPPH) and 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS) radical-scavenging activity of yacon extracts following heat treatment were measured. The browning index, free polyphenolic content, and antioxidant activities in the extracts were significantly increased (p<0.05) with both increased heating temperature and time, while bound polyphenolic levels were decreased. The levels of free phenolic and flavonoid compounds in the yacon extract heated to $121^{\circ}C$ for 60 min were increased by 1.2 and 1.1 folds compared to raw yacon respectively. Moreover, DPPH and ABTS radical-scavenging activities of the yacon heated to $121^{\circ}C$ for 60 min were 1.7 fold and 2.0 fold higher, respectively, than those of raw yacon. A significant (p<0.01) correlation was observed among browning intensity, free and bound phenolic and flavonoid levels, and DPPH and ABTS radical-scavenging activities in heated yacon extract. Thus, heat treatment can be used as a method to enhance the antioxidant compound content in and the antioxidant activity of yacon.

• The Korean Journal of Food And Nutrition
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• v.11 no.2
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• pp.237-242
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• 1998

This study was carried out to process canned ark shell with highly quality by management of proper processing conditions for prevention of oxidation and discoloration by heating. Ark shell has hemoglobin as blood pigment in red blood shell which same as other cockles. Hemoglobin is easy to come oxidation and browning reaction, and it has large contents of carotenoid as meat pigment. Proximate compositions in ark shell were 76.9% of moisture, 18.1% of crude protein, 1.8% of crude lipid, 1.3% of carbohydrate and 1.6% of crude ash. And contents of carotenoid and hemoglobin were 0.67~1.02mg% and 0.98~1.64g/dl, respectively. When the living ark shell was soaked in 2% NaCl solutions, about 89% of mud was removed after 10 hours soaking, and over 91% was removed when the pH was adjusted to 7.5. Carotenoid pigment were prepared that extracted from ark shell by using acetone. And determined visible spectrum were two peak at 452nm and 687nm, and λmax were 452nm. During thermal treatment at 95$^{\circ}C$, 111$^{\circ}C$, 116$^{\circ}C$ and 121$^{\circ}C$ for 60 minutes, retention ratio of carotenoid were 71.8%, 66.8%, 64.4% and 36.5%, and after 120 minutes retention ratio were 56.6%, 30.6%, 30.3% and 17.2%, respectively. When heated at 95$^{\circ}C$, 111$^{\circ}C$, 116$^{\circ}C$ and 121$^{\circ}C$, formation of browning material were increased at high temperature and long time treatment.

• Journal of Food Hygiene and Safety
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• v.38 no.3
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• pp.89-98
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• 2023

Currently, no guidelines exist regarding the maximum residues of pesticides in edible oil which is a processed food commonly consumed in Korea. This lack of guidelines hinders the evaluation of the safety of edible oil in terms of pesticide contamination. In this study, an analysis method based on heat distillation and GC-MS/MS was established by optimizing the extraction and purification procedure for 68 pesticides. Important variables in the thermal distillation procedure included heating temperature and time, and we found the nitrogen flow rate as a mobile phase and the type of dissolving solvent were not considerably affected. The determination coefficient (R²) of the residual pesticide was 0.99 or higher, and the quantitative limit (LOQ) was 0.01-0.02 mg/L. The average recovery rate (n=5) was 66.1-120.0% and the relative standard deviation was lower than ±10% when 68 pesticides were spiked at concentrations of 0.01-0.02, 0.1, and 0.5 mg/L. In addition, the within-laboratory precision was less than ±11%, meeting the Korea Food and Drug Safety Evaluation Institute's Guidelines on Standard Procedures for Preparing Food Testing Methods (2016). Therefore, the test method developed in this study can be used as a test method for managing the safety of the residual pesticide concentration in edible oil.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.6
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• pp.520-528
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• 1987

Quality stability of roasted lavers during heat treatment and storage was investigated measuring the changes in pigments including chlorophyll a, carotenoids and biliproteins, fatty acids and free amino acids as the major quality factors. In roasting of fried lavers, carotenoids were found to lie more stable than chlorophyll a, and biliproteins were most heat labile. The overall heat stability of the pigments depended upon heating time and temperature. Chlorophyll a and carotenoids were retained more than $90\%$ in the casts of roasting for 90 min. at $60^{\circ}C;\;60min.\;at\;80^{\circ}C;\;10\;min.\;at\;100^{\circ}C;\;or\;5min.\;at\;150^{\circ}C$ while biliproteins remained about $70\%$. The lipids of dried lavers including polyunsaturated fatty acids appeared rather heat stable when compared to the stability of pigments under the same conditions of roasting. Spray of sesame oil or seasoning solutions on the surface of lavers after roasting seemed desirable for stabilizing pigments and free amino acids during storage particularly at low water activity. And that was also benefit for the protection of polyenoic fatty acids from rapid progress of oxidation during storage. Free amino acids were reduced fast during roasting, especially most of threonine and glycine while glutamic acid was rapidly lost during the storage.