• Food Science and Preservation
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• v.18 no.4
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• pp.546-551
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• 2011

Response surface methodology (RSM) was used for the microwave-assisted extraction (MAE) of the effective components of grape seed, such as its antioxidative and nitrite-scavenging abilities. Microwave power (2,450 MHz, 0-160W), ethanol concentration (0-100%), and MAE time (1-5 min) were used as independent variables (Xi) for the central composite design to yield 16 different MAE conditions. The optimum MAE conditions were predicted for the dependent variables of the extracts, such as the total phenolic content ($Y_1$) antioxidative ability ($Y_2$), and nitrite-scavenging ability ($Y_3$), depending on different microwave powers, ethanol concentrations, and MAE times. The determination coefficients ($R^2$) of the regression equations for the dependent variables ranged from 0.8024 to 0.9498. The maximal values of each dependent variable were predicted at different MAE conditions, as follows: 3.19% total phenolic content at 142.32W, 44.30% ethanol, and 4.36 min, and 1.22 antioxidative ability at 84.44W, 56.60% ethanol, and 3.28 min. More than 99.5% nitrite-scavenging ability was predicted at pH 1.2-3.0, 30.80-106.58W, 49.32-55.18% ethanol, and 3.72-4.58min, respectively. The results indicated that the total phenolic content and anti oxidative ability showed a higher correlation with each other in that they were more influenced by microwave power than by the other variables, while the nitrite-scavenging ability was largely influenced by the ethanol concentration.

• Korean Journal of Agricultural Science
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• v.26 no.1
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• pp.50-57
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• 1999

The purpose of this study was to determine the thermal inactivation of L. monocytogenes KCTC3443 in liquid culture heated in the controlled microwave system and in the conventional heating method. Furthermore, we have carried out a comparative study on the thermal and nonthermal microwave effects on microorganisms, pasteurized using a controlled microwave energy specially designed apparatuses and a water bath. For the automatic temperature control during microwave heating, the real time data acquisition and computation system is designed with BASIC routine. The automatic temperature control system used in the experiments perform relatively stable control at the experiment temperature of 55, 65, $75^{\circ}C$ and $85^{\circ}C$ for 30 minutes. The effects of microwave heating on liquid cultures was compared with that of conventional heating. The results show that microwave radiation, while being slightly quicker than conventional heating, still reduces effectively the number of pathogenic bacteria during heating for a limit time in liquid cultures. While no particular differences between microwave heating and conventional heating was not observed in the thermal inactivation of L. monocytogenes at 55, 65, $75^{\circ}C$ and $85^{\circ}C$ for 30 min., respectively. Microwave heating is, therefore, substantially not effective in inactivating L. monocytogenes in liquid culture than conventional heating method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.12
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• pp.2263-2268
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• 2008

We investigated the malfunction and destruction characteristics of microcontroller devices under high power electromagnetic(HPEM) wave by magnetron. HPEM was rated at a microwave output of 0 to 1,000 W, at a frequency of 2,450${\pm}$50 MHz and was radiated from the open-ended standard rectangular waveguide(WR-340) to free space. The influence of different reset-, clock-, data-, and power supply-line lengths has been tested. The variation of the line length was done with flat cables. The susceptibility of the tested microcontroller devices was in general much influenced by clock-, reset-, and power supply-line length, little influenced by data-line length. Further the line length was increased, the malfunction threshold was decreased as expected, because more energy couples to the devices. The surfaces of the destroyed microcontroller devices were removed and the chip conditions were investigated with microscope. The microscopic analysis of the damaged devices showed component and bondwire destructions such as breakthroughs and melting due to thermal effects. The obtained results are expected to provide fundamental data for interpreting the combined mechanism of microcontroller devices in an intentional microwave environment.

• Korean Journal of Food Science and Technology
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• v.31 no.5
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• pp.1392-1396
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• 1999

This work was to apply the microwave energy to HTST pasteurization of milk in order to prevent undesirable quality changes due to the fouling and overheating on the surface of heat exchanger. A continuous tubulartype microwave pasteurization system was designed using a domestic microwave oven(800w and 2,450MHz). Raw milk was HTST pasteurized$(at\;72^{circ}C\;for\;15\;sec)$ by three methods; by heating in a stainless steel tube immersed in a hot water bath(MP0), by heating in a microwave cavity to a desired temperature and then holding in a hot water bath(MP1) and by both heating and holding in a microwave cavity(MP2). The microbial quality based on the total plate count and Psychotrophic bacterial count was in the order MP0, MP2 and MP1 ; however, the quality difference was not significant(p<0.05) when the initial microbial numbers were involved in the statistical analysis. In addition, the three samples pasteurized by different methods showed the similar microbial quality based on the coliform count and phosphatase activity. The similar microbial quality of the three samples supports the potential use of microwave energy for the pasteurization of milk and other fluid food products.

• Korean Journal of Food Science and Technology
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• v.18 no.6
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• pp.413-420
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• 1986

This study was attemtped to improve the conventional processing method and to establish the basic data for evaluating the product suitabilities of dried loach. The semidressed raw material were salted in 15% NaCl solution for 15 minutes and dried to contain about 44% of water, and then heated about 10 minutes at $80^{\circ}C$ controlled by microwave (2,450 MHz). The moisture content of monolayer value for the product showed 5.34% and its water activity was 0.28. The optimum relative humidity for the storage was recognized to be from 32% to 44%. The average shelf life around the year of the Nylon-PVC-PE $(40\;{\mu})$ packed product in domestic circulation market was estimated as 207.4 days. In comparison with raw material, the contents of the major amino acids, glutamic acid, alanine and valine in the product were shown to be slightly increased, while the level of lysine, aspartic acid and methionine were slightly decreased. The contents of saturated fatty acids and oleic acid were shown to be slightly increased, while the other fatty acids tended to be slightly decreased.

• Journal of the Korean Society of Food Science and Nutrition
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• v.20 no.5
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• pp.461-466
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• 1991

For the purpose of improving storability and process adaptability of potato, we carried out an experiment to investigate the effects of microwave heating on the total lipid content and fatty acid composition of the potatoes in storage. The samples were made by powdering potatoes exposed to the microwave energy in a 560W, 2,450MHz oven for 0, 60, 120 and 180 seconds respectively. From the examination of the samples stored at th temperature of $25{\pm}1^{\circ}C$ for 12 months, the following results were obtained. As an over-all tendency, the longer the samples were heated and the longer they were stored, the total lipid content decreased but the microwave-heated samples showed decreasing rates less than those of the controls for the whole storage periods. As major fatty acids of the potato flour, linoleic acid (30.92 %), palmitic acid (29.34 %), linolenic acid (8.90 %) and stearic acid (8.23 %) were detected from the samples. The longer the samples were exposed with microwave, unsaturated fatty acids like 18:2, 18:3 increased. generally with the lapse of storage time, saturated fatty acids increased while unsaturated ones decreased. But in the samples heated with microwave, we observed an apparent suppression of the increasing rate of the saturated fatty acids and the decreasing rate of the unsaturated fatty acids, and the suppressing effects turned out to be proportional to the length of microwave heating.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.8
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• pp.990-996
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• 2006

This research was conducted to evaluate the changes in allergenicity of shrimp by physical treatments using competitive indirect enzyme-linked immunosorbent assay (Ci-ELISA). Shrimp was subjected to physical treatments such as high hydrostatic pressure (HHP), sonication, autoclave and microwave. Heat-stable protein (HSP) purified from raw shrimp was used as a major allergen. The binding ability of monoclonal IgG and shrimp-allergic patients' IgE to HSP treated with HHP decreased, increasing the pressure up to 400 MPa. Especially, it became less than 50% at 400 MPa. The binding ability of mAb to HSP treated with sonication (10, 20, 30 and 60 min) decreased with the treated time. Especially, it became less than 60% with the treatment for 60 min. The allergenicity change of HSP treated with autoclave and microwave little decreased. The binding ability of mAb to HSP during the treatment for 20 min became more than 70%. The results suggest that allergenicity of HSP in raw shrimp be more easily lost by HHP or sonication treatment than by autoclave or microwave treatment.

• Journal of the Korean Society of Food Science and Nutrition
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• v.13 no.3
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• pp.268-274
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• 1984

The purpose of this study was to investigate the physico-chemical effects of a potato starch and a purified potato starch under the condition of the microwave heating. They were exposed to the microwave energy in a 950 W, 2,450 MHz oven for 30 through 120 seconds. As the microwave heating time was increased, the contents of moisture and the crude fat of the samples were remarkably decreased irrespective of the starch composition, but on the other hand the contents of crude ash was slightly decreased and the crude protein was almost unchanged. The rings of crystallinity come to gradually changed in the X-ray diffraction pattern, and then the only 1 ring, of which interplanner spacing is wide, is changed strikingly. As the microwave heating time is increased, the starch granules which observed by a scanning electron microscope were broken partially with a special form, and the granules of purified potato starch were broken faster than those of potato starch. With the same condition that the microwave heating time was increased, while the gelatinization temperature comes to fall, the swelling power and the solubility were increased. Besides these, while the gelatinization temperature of the purified potato starch was lower than that of the potato starch, both the swelling power and the solubility of the purified potato starch is higher than those of the potato starch.

• Journal of Microbiology and Biotechnology
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• v.17 no.5
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• pp.847-852
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• 2007

This study investigated an efficient method for the extraction of astaxanthin from the red yeast Xanthophyllomyces dendrorhous. The extraction process comprised three steps: 1) cultivating the yeast; 2) treating the yeast culture suspension with microwaves to destroy the cell walls and microbodies; and 3) drying the yeast and extracting the astaxanthin pigment using ethanol, methanol, acetone, or a mixture of the three as the extraction solvent. Ultimately, various treatment tests were performed to determine the conditions for optimal pigment extraction, and the total carotenoid and astaxanthin contents were quantified. A frequency of 2,450 MHz, an output of 500 watts, and irradiation time of 60 s were the most optimum conditions for yeast cell wall destruction. Furthermore, optimal pigment extraction occurred when using a cell density of 10g/l at $30^{\circ}C$ over 24 h, with a 10% volume of ethanol.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.2
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• pp.17-29
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• 2020

The objective of this study was to find an optimum methane yield condition in anaerobic digestion of sewage sludge with microwave pretreatment. The pretreatment process was carried out using a lab scale industrial microwave unit (2,450 MHz frequency). The digestion efficiency of pretreated sludge was evaluated by biochemical methane potential (BMP) test. Box-Behnken design and Response Surface Analysis (RSA) were applied to determine the optimal combination of sludge mixing ratio (0 to 100%), power (400 to 1600 W), holding time (0 to 10 min) and pretreatment temperature (60 to 100℃). BMP test results showed that Volatile Solid (VS) removal efficiency was up to 48% at a condition of 0% for mixing ratio, 1600 W for power, 5 min for holding time, and 80℃ for pretreatment temperature. Methane production was up to 832.3 mL/g VS_removed at a condition of 50% for mixing ratio, 1000 W for power, 5 min for holding time, and 80℃ for pretreatment temperature. The results of the variance analysis (ANOVA) showed that the p-value of the power and pretreatment temperature among the independent variables were significant (p<0.05), and in particular, the pretreatment temperature significantly affected on the solubilization and methane production. The optimum condition for the maximum methane yield (847 mL/g VS_removed) was consist of 38.4% of mixing ratio, 909.1 W of power, 4.1 min of holding time, and 80℃ of temperature within the design boundaries.