• 한국식품영양학회지
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• 제24권4호
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• pp.740-745
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• 2011

Ohmic heating uses electric resistance heat which occurs equally and rapidly inside food when an electrical current is passed throught. In this study, we observed the physical & chemical characteristics changes which occurs in soybean protein during heating denaturation by using ohmic and conventional heating. After the ohmic heating process, we could not find any change of the primary protein structure in the denaturated soy protein samples. However, the rate of imbibed water(RIW) of the ohmic samples was 2 times faster than that of the conventional samples. Also the ANS-surface hydrophobicity was decreased, which is very closely related to RIW. In the differential scanning calorimeter(DSC) analysis result, all 7S soyprotein fraction samples were completely denaturated by ohmic and conventional heating. However, the 11S samples were completely denatured only by ohmic heating. According to the DSC result, we decided that soyprotein was damaged by temperature and electrical current during ohmic heating. The damage of electrical current was a cause of the characteristic changes.

• Journal of Microbiology and Biotechnology
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• 제12권2호
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• pp.183-188
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• 2002

The ohmic heating of foods for sterilization provides a shorter come-up time compared to conventional thermal processes. The electric fields as well as the heat generated by ohmic heating facilitate germicidal effects. In the present study, the effect of ohmic heating on the structure and permeability of the cell membrane of yeast cells, Saccharomyces cerevisae, isolated from Takju (a traditional Korean rice-beer), was investigated. The ohmic heating was found to translocate intracellular protein materials out of the cell wall, and the amount of exuded protein increased significantly as the electric field increased from 10 to 20 V/cm. As higher frequencies were applied, more materials were exuded. Compared to conventional heating, more amounts of proteins and nucleic acids were exuded when these cells were treated with ohmic heating. The molecular weights of the major exuded proteins ranged from 14 kDa to 18 kDa, as analyzed by Tricine-SDS PAGE. A TEM study also confirmed the leakage of cellular materials, thus indicating irreversible damage to the cell wall by ohmic heating. It was, therefore, concluded that the electric fields generated by ohmic heating induced electroporation, causing irreversible damage to the yeast cell wall and promoting the translocation of intracellular materials.

• 한국식품영양학회지
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• 제27권1호
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• pp.112-119
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• 2014

Ohmic heating uses electric resistance heat which occurs equally and rapidly inside food when the electrical current is transmitted into. Prior to the study, we have researched the potato starch's thermal property changes during ohmic heating. Comparing with conventional heating, the gelatinization temperature and the range of potato starch treated by ohmic heating are increased and narrowed respectively. Herein, we have studied thermal property changes of wheat, corn, potato and sweet potato starch by ohmic heating as well as conventional heating. And then we measure the water holding capacity of starches. Annealing of starch is a heat treatment method heated at 3~4% below the gelatinization point. This treatment changes the starch's thermal property. In the DSC analysis of this study, the $T_o$, $T_p$, $T_c$ of all starch levels have increased, and the $T_c$-$T_o$ narrowed. In the ohmic heating, the treatment sample is extensively changed but not with the conventional heating. From the ohmic treatment, increases from gelatinization temperature are potato ($8.3^{\circ}C$) > wheat ($5.3^{\circ}C$) > corn ($4.9^{\circ}C$) > sweet potato ($4.5^{\circ}C$), and gelatinization ranges are potato ($7.9^{\circ}C$), wheat ($7.5^{\circ}C$), corn ($6.1^{\circ}C$) and sweet potato ($6.8^{\circ}C$). In the case of conventional treatment, water holding capacity is not changed with increasing temperature but the ohmic heating is increased. Water holding capacity is related to the degree of gelatinization for starch. This result show that when treated with below gelatinization temperature, the starches are partly gelatined by ohmic treatment. When viewing the results of the above, ohmic treatment is enhanced by heating and generating electric currents to the starch structure.

• 한국식품영양학회지
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• 제28권1호
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• pp.126-133
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• 2015

Ohmic heating uses electric resistance heat which occurs equally and rapidly inside food when the electrical current is transmitted into. Prior to the study, we have researched the potato starch's thermal property changes during ohmic heating. Comparing with conventional heating, the gelatinization temperature and the range of potato starch treated by ohmic heating are increased and narrowed respectively. This result is appeared equally at wheat, corn and sweet potato starch. At this study, we treated potato, wheat, corn and sweet potato starch by ohmic/conventional method and observed change of external structure by microscope and internal structure by X-ray diffractometer. Conventional heated at $55^{\circ}C$ potato starch was not external structural changes. But ohmic heated potato starch is showed largely change. Some small size starch particle were broken or small particles are made of larger particle together or small particles caught up in the large particle. Changes in ohmic heated potato starch at $60^{\circ}C$ was greater. The inner matter came to an external particle burst inside and only the husk has been observed. The same change was observed in the rest of the starch. The change of internal structure of potato starch was measured using X-ray diffraction patterns. There was no significant difference between ohmic and conventional heating at $55^{\circ}C$. But almost every peak has disappeared ohmic at $60^{\circ}C$. Especially $5.4^{\circ}$ peak to represent the type B was completely gone. When viewed from the above results, external changes with change in the internal crystal structure of the starch particles were largely unknown to appear. In conclusion, during ohmic heating changes of starch due to the electric field with a change in temperature by the heating was found to have progressed at the same time.

• 한국식품영양학회지
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• 제30권4호
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• pp.689-695
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• 2017

Ohmic heating is an internal heating method based on the principle that when an electrical current passes through food, electric resistance heat is uniformly generated internally by food resistance. Previous studies indicate that the thermal properties, external structure, internal structure, and swelling power of ohmic heat treated starch of various starches, such as potato, wheat, corn, and sweet potato, differed from those of conventional heating at the same temperature. In this study, the pasting property of starch, treated with ohmic and conventional heating, were measured by RVA (Rapid Visco-Analyzer). Our results show that as the ohmic heating temperature increased, the PV (Paste Viscosity) of the starch decreased significantly, and the PT (Pasting Temperature) increased. Changes in PV and PT indicate that the swelling of starch remains unchanged by ohm heating. The HPV (Hot Paste Viscosity), CPV (Cold Paste Viscosity) and SV (Setback Viscosity) of ohmic heated starch also differed from the conventional heated starch. The pasting property is similar to the viscosity curve of common cross-linked modified starch. In this experiment, we further confirm the similarity with modified starch and its usability.

• 한국식품영양학회지
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• 제32권4호
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• pp.304-311
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• 2019

Ohmic heating is a heating method based on the principle when an electrical current passes through food. Since this method is internal, electrical current damage occurred during heating treatment. The results of ohmic heated starch's external structure, X-ray diffraction, DSC analysis and RVA were differed from those of conventional heating at the same temperature. Several starches changed more rigid by structure re-aggregation. This change in starch was caused by change of physical, chemical, rheological property. The rheology of ohmic heated potato and corn starch of different heated methods were compared with chemically modified starch. After gelatinization, sample starch suspension (2%, 3%) measured flow curves by rheometer. Cross-linked chemically modified starch's shear stress was decreased with degree of substitution reversibly. Ohmic heated more dramatic, at $60^{\circ}C$. Potato starch's shear stress was less than commercial high cross-linked modified starch. Flow curves of potato starches measured at $4^{\circ}C$, $10^{\circ}C$, $20^{\circ}C$. Showed that Ohmic heated potato starch's shear stress ranging between $4^{\circ}C$ and $20^{\circ}C$ was narrower than modified starch. According to this study, ohmic heated potato starch can be used by decreasing viscosity agent like cross-linked modified starch.

• 한국식품영양학회지
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• 제25권4호
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• pp.1068-1074
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• 2012

Ohmic heating uses electric resistance heat which occurs equally and rapidly inside of food when electrical current is flown into. In other study, we researched about soybean protein's characteristic changes by ohmic heating. Nevertheless treated same temperature, denaturation of soybean protein were accelerated by ohmic heating than conventional heating. In this time, we studied thermal property change of potato starch by ohmic heating besides conventional heating. For this purpose, potato starch was heated at same subgelatinization temperature by ohmic and conventional heating. And thermal properties were tested using DSC. Annealing of starch is heat treatment method that heated at 3~4% below the gelatinization point. DSC analysis results of this study, the $T_o$, $T_p$, $T_c$ of potato starch levels were increased, whereas $T_c{\sim}T_o$ was narrowed. This thermal property changes appear similar to annealing's result. It is thought the results shown in this study, because the heating from below the gelatinization point. 6, 12, 24, 72, and 120 hours heating at $55^{\circ}C$ for potato starch, $T_o$, $T_p$, $T_c$ values continue to increased with heating time increase. The gelatinization temperature of raw potato starch was $65.9^{\circ}C$ and the treated starch by conventional heating at $55^{\circ}C$ for 120 hr was $72^{\circ}C$, ohmic was $76^{\circ}C$. The gelatinization range of conventional (72 hr) was $10^{\circ}C$, ohmic was $8^{\circ}C$. In case of 24 hours heating at 45, 50, 55, 60, $65^{\circ}C$ for potato starch, the result was similar to before. $T_o$, $T_p$, $T_c$ values continue to increased and gelatinization range narrowed with heating temperature increase. In case of conventional heating at $60^{\circ}C$, the results of gelatinization temperature and range were $70.1^{\circ}C$ and $9.1^{\circ}C$. And ohmic were $74.4^{\circ}C$ and $7.5^{\circ}C$. When viewed through the results of the above, the internal structure of starch heated by ohmic heating was found that the shift to a more stable form and to increase the homology of the starch internal structure.

• 한국식품과학회지
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• 제26권6호
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• pp.791-798
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• 1994

점성이 높고 열전도도가 낮아 기존의 열전도 가열방식으로는 효과적인 살균이 어려운 고추장, 된장 등의 페이스트상 식품의 효율적인 살균 공정을 개발하기 위한 기초 연구로서 전기 저항열(Ohmic heaing)을 이용한 실험실 규모의 정치 회분식 가열 시스템을 고안하고 전기적 요소가 가열 특성에 미치는 영향을 연구 검토하여 다음의 결론을 얻었다. 1. 고추장과 된장의 상온에서의 전기 전도도는 각각 1.865 S/m 2.510 S/m였으며, Ohmic heating에 의하여 온도가 증가함에 따라 전기전도도가 거의 비례적으로 증가하는 전기적 특성을 나타내었다. 2. 상용 주파수(60 Hz)에서는 전압을 증가시킬수록 비가열 속도$(^{\circ}C/g{\cdo}s)$가 거의 비례적으로 증가하였다. 일정한 전압에서 주파수를 증가시켰을 때 1KHz 이상에서부터 주파수의 증가에 따라 비가열 속도는 급격히 증가하여 고추장의 경우에는 5KHz에서 최고 가열속도 틀 나타내었으며 그 이상의 주파수에서는 감소하였으나 된장의 경우에는 계속 증가하여 실험범위의 최고값인 20KHz에서 최대 가열속도를 나타내었다. 3.고추장의 경우 전압, 전극 간격 및 시료량과 비가열속도와외 관계를 검토한 결과 비가열 속도 $35^{\circ}C/g{\cdot}s$ 이하일때 균일하게 가열이 이루어졌으며, 그 이상의 가열속도에서는 전극 부근에서 cake 생성 현상이 일어나 효과적으로 가열되지 않았다. 4. Ohmic heating 동안에 시료의 위처에 따른 온도 분포를 관찰한 결과 낮은 주파수 범위에서는 시료의 표면과 중간 부위외 온도차가 거의 없이 균일하게 급속히가열되었다. 그러나 5 KHz 이상의 높은 주파수 영역에 서는 표피 효과로 인하여 시료의 중심과 표면사이에 $10^{\circ}C$내외의 온도차가 생겼으며, 전극 부근의 온도가 중심부근 보다 5${\sim}10^{\circ}C$ 높았으므로 적절한 주파수의 선정이 중요하였다. 5. 고추장과 된장의 수분함량이 습량 기준으로 30% 이하일 때는 전류가 흐르지 않아 Ohmic heating의 적용이 불가능 하였으나, 30% 이상에서는 수분함량의 증가에 따라 가열속도는 급속히 증가하였다.

• 한국식품과학회지
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• 제47권4호
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• pp.474-479
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• 2015

연속식 옴가열 장치를 이용한 고추장을 베이스로 한 모델 식품에 대한 가열 살균 연구를 진행하여, 옴가열을 이용한 소스 살균에 필요한 기초 데이터를 수집하였다. 옴가열 시 점도에 상관없이 $100^{\circ}C$까지 고르게 상승하였으나, 점도가 높을수록 전기전도도와 가열속도가 낮아져 살균력이 감소하는 것으로 나타나, 저점도 식품이 옴가열을 이용한 가열 및 살균에 있어 더 유용하다는 것을 알 수 있었다(13,14). 재래가열 후의 살균도는 65.4-75.4%, 옴가열 시는 89.5-95.0%로 살균력이 더 우수하였다. 향후 연속식 옴가열 장치의 살균효과를 더 높이기 위해서는 여러 개의 셀 연결 방식을 통해 한 개의 셀에서 온도를 조금씩 상승시켜 스케일 생성을 방지하는 연구와 셀 통과시 빠른 온도 상승에 의한 점도 변화로 살균 처리량이 변하기 때문에 최적 셀 조합 및 가열살균 조건에 대한 충분한 고찰이 필요할 것으로 생각된다.

• Applied Biological Chemistry
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• 제41권6호
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• pp.431-436
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• 1998

통전가열(ohmic heating)을 사과주스의 가열 살균에 적용해보기 위하여 가열기 형태와 전압, 파형, 주파수 등 전기적 요소가 사과주스 모델용액의 통전가열 속도에 미치는 영향을 알아보았다. 100 VAC, 60 Hz의 상용전류를 이용한 통전가열시 컬럼형 가열기에서 전극간의 간격이 29, 22, 17 mm로 줄어듬에 따른 모델용액의 가열속도는 $7.8,\;21.0,\;47.4^{\circ}C/min$으로 크게 증가하였으며 또한 전극의 수를 병렬로 1, 2, 3쌍으로 증가시킬 시에도 $29.2,\;49.8,\;74.6^{\circ}C/min$으로 비례적으로 증가하여 전극의 간격이 작을수록, 전극의 표면적이 증가할수록 가열속도는 크게 빨라지는 것으로 나타났다. $60\;Hz{\sim}60\;kHz$ 범위의 주파수 변화에 따른 가열속도 차이는 나타나지 않았으며 파형에 따른 가열속도는 positive saw tooth wave를 제외하고 변화가 거의 없었다. 전압을 40에서 100 VAC로 높임에 따라 가열속도는 $9.5^{\circ}C/min$에서 $83^{\circ}C/min$로 크게 증가하여 전압과 가열속도는 정비례 관계가 있음을 알 수 있었다. 통전가열과 상업적 살균방법으로 제조한 사과주스 간에는 이화학적 특성의 차이가 없었다.