• Carbon letters
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• 제16권2호
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• pp.93-100
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• 2015

Surface modified carbon felts were utilized as an electrode for the removal of inorganic ions from seawater. The surfaces of the carbon felts were chemically modified by alkaline and acidic solutions, respectively. The potassium hydroxide (KOH) modified carbon felt exhibited high Brunauer-Emmett-Teller (BET) surface areas and large pore volume, and oxygen-containing functional groups were increased during KOH chemical modification. However, the BET surface area significantly decreased by nitric acid ($HNO_3$) chemical modification due to severe chemical dissolution of the pore structure. The capability of electrosorption by an electrical double-layer and the efficiency of capacitive deionization (CDI) thus showed the greatest enhancement by chemical KOH modification due to the appropriate increase of carboxyl and hydroxyl functional groups and the enlargement of the specific surface area.

• Journal of Photoscience
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• 제9권2호
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• pp.302-304
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• 2002

pharaonis phoborhodopsin (ppR), a photophobic sensor of haloalkaliphilic bacteria, Natronobacterium phar-aonis, has retinal as a chromophore covalently bound to Lys in G-helix via a protonated Schiff base (PSB), as is the same as bacteriorhodopsin (bR). For ppR, the corresponding counter-ion is Asp residue (Asp75) located in C-helix. Here we investigated the influence of the protonated state of this counter-ion and its location on the chromophore configuration. Under alkaline condition, the chromophore configuration of D75E mutant was analyzed by HPLC. D75E had a much larger content of 13-cis isomer: the ratio of 13-cis to all-trans was 6:4 while the wild-type had this ratio of 1 :9. On the other hand, under acidic condition where Glu was associated, D75E had no 13-cis retinal isomer. Mutants whose Asp75 was replaced by neutral amino acids (D75N and D75Q) did not contain 13-cis retinal. Furthermore, retinal isomer compositions and the change in the visible ab- sorption spectra (indicating the dissociation state of Glu75) were measured under varying pH, and these were almost the same dependencies. These results indicate that an important factor determining the 13-cis isomer content is the presence of negative charge of the counter-ion against PSB, but not the size of this residue. Com- parison between the wild-type and D75E in alkaline solutions indicates the influence of the location of the counter-ion.

• Bulletin of the Korean Chemical Society
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• 제33권7호
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• pp.2265-2268
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• 2012

Aqueous solution of oxygenated Direct yellow 12 dye has been evaluated spectrophotometrically as a possible gamma rays dosimeter. The neutral (pH-7), alkaline (pH-12.5) and acidic (pH-5.5) aqueous solution of the dye were prepared and exposed to various gamma doses. Absorption spectra of unirradiated and irradiated solutions were recorded at 400 nm peak. The increase in absorbance with the increase in irradiation dose was observed from 1 to 6 kGy. The stability response of the dye solution for different environmental conditions such as temperature (low & high), light and darkness were investigated during post irradiation storage for ten days. The dye solution showed high stability in darkness for the studied period. The optical density of the dye solution was found to be decreased at high temperature storage.

• Applied Biological Chemistry
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• 제39권3호
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• pp.245-248
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• 1996

식품첨가물로서의 활용가능성을 검색하기위해, 한국산 유색미(Oryza sutiva var. Suwon 415)의 주요색소인 cyanidin 3-히ucoside의 열안정성과 pH 변화에 따른 UV/Vis 스펙트럼의 변화에 대해 연구하였다. 유색미의 안토시아닌 색소는 산성(pH 2.0)과 염기성(pH 9.0) 완충용액에서 각각 강한 적색과 청색을 나타내었고 열에 의한 색소의 분해반응은 20mM phosphate (PH 2.0)와 20mM CHES (pH 9.0) 완충용액에서 $50{\sim}95^{\circ}C$의 온도범위에서 수행되었다. 색소의 분해정도는 UV/Vis 스펙트럼의 변화를 측정하여 결정하였으며, 350nm (pH 2.0)와, 275, 310, 및 405nm (pH9.0)에서 isosbestic를 나타내었다. 이 결과는 색소분해반응이 1차 반응임을 의미한다. 유색미 안토시아닌은 산성조건에서 매우 안정하였고 염기성조건에서도 비교적 안정하였으며, 반감기는 $70^{\circ}C$에서 각각 50.3h과 0.6h이었다. 색소분해반응의 활성화에너지$(E_a)$와 Arrhenius frequence facto(A)는 pH 2.0에서는 26.9kcal $mol^{-1}$과 $6.0{\times}10^{11}\;s^{-1}$이었고, pH 9.0에서는 152Kcal $mol^{-1}$과 $1.4{\times}10^{6}\;s^{-1}$이었다.

• Corrosion Science and Technology
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• 제14권4호
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• pp.166-171
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• 2015

Knowledge of how metal releases from the stainless steels used in food processing applications and cooking utensils is essential within the framework of human health risk assessment. A new European standard test protocol for testing metal release in food contact materials made from metals and alloys has recently been published by the Council of Europe. The major difference from earlier test protocols is the use of citric acid as the worst-case food simulant. The objectives of this study were to assess the effect of citric acid at acidic, neutral, and alkaline solution pH on the extent of metal release for stainless steel grades AISI 304 and 316, commonly used as food contact materials. Both grades released lower amounts of metals than the specific release limits when they were tested according to test guidelines. The released amounts of metals were assessed by means of graphite furnace atomic absorption spectroscopy, and changes in the outermost surface composition were determined using X-ray photoelectron spectroscopy. The results demonstrate that both the pH and the complexation capacity of the solutions affected the extent of metal release from stainless steel and are discussed from a mechanistic perspective. The outermost surface oxide was significantly enriched in chromium upon exposure to citric acid, indicating rapid passivation by the acid. This study elucidates the effect of several possible mechanisms, including complex ion- and ligand-induced metal release, that govern the process of metal release from stainless steel under passive conditions in solutions that contain citric acid.

• Journal of Microbiology and Biotechnology
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• 제8권2호
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• pp.178-181
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• 1998

An exopolysaccharide, designated as A49-Pol, was produced from Bacillus polymyxa KCTC 8648P in nitrogen sufficient conditions. The viscosity of the culture broth increased up to $2\times10^4$cP in 38 hours of culture and then decreased to $1.5\times10^4$CP at 48 hours. The $1.0\%$ (w/v) solution of purified A49-Pol represented pseudoplasticity with a viscosity of $2.7\times10^4$cP which was two times higher than xanthan at the same concentration. The viscosity of the A49-Pol solution was also greatly affected by its concentration in comparison with the xanthan solution. The viscosity of $1.0\%$ A49-Pol solution was 930-fold higher than its $0.2\%$ solution, whereas the corresponding viscosities of xanthan solution experienced only l7-fold difference. The viscosity was observed to be maximum at pH 7.0 in both A49-Pol and xanthan solutions, and gradually decreased as the pHs of the polysaccharide solutions went to acidic or alkaline regions. The viscosity of A49-Pol solution was very sensitive to temperature compared to xanthan and decreased with increasing temperature. The viscosity of $0.6\%$ solution of A49-Pol was 8,100 cP at $10^{\circ}C$ and 55 cP at $50^{\circ}C$. The viscosity was also affected by the presence of surfactants such as Span 20 and Triton X-l00 ; with $0.5\%$ Triton X-l00 (v/v), the viscosity of A49-Pol solution increased by $50\%$.

• 한국가정과학회지
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• 제9권1호
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• pp.43-50
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• 2006

The main colorant of Chelidonium majus extracts is a berberine which shows relatively good dyeability onto silk fabrics in the appropriate dyeing conditions without mordant, But cotton fabrics are difficult to dye with berberine because of the low substantivity the cationic to cellulosic fibers. we treated cotton fabrics using three types of polycarboxylic acid, DL-malic acid, citric acid, 1,2,3,4-butanetetracarboxylic acid(BTCA) to increase dyeability of Chelidonium majus extracts onto cotton fabrics. As a result the cotton fabrics treated with polycarboxylic acid could be dyed with Chelidonium majus extracts and also showed yellow vividly. The dye uptake were increased with increasing the number of carboxy groups. And so dye uptake resulted the largest in the BTCA solutions which have four carboxylic groups in the molecular unit. The optimal dyeing temperature a of Chelidonium majus extracts onto polycarboxylic acid treated cotton fabrics were $60^{\circ}C$. The dye equilibrium was reached 20 minutes after dyeing. Neutral pH of dye solutions showed in higher K/S value than acidic or alkaline conditions. But the colorfastness to washing and light according to polycarboxylic acid treat was not enhance.

• 한국식품과학회지
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• 제33권6호
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• pp.664-668
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• 2001

전통 천연 색소원인 홍화 꽃잎으로부터 추출한 적색소인 carthamin을 식품색소로 활용하기 위한 기초연구로 carthamin의 여러 가지 이화학적 안정성을 분해속도와 반감기를 구하여 조사하였다. Carthamin은 산성에서는 매우 불안정하여 반감기가 pH 3.0에서는 5.26시간, pH 5.0에서는 4.9시간으로 매우 짧았으며 중성(pH 7.0)에서는 11.1시간, 알칼리 조건(pH 11.0)에서는 45.1시간으로 조금 더 안정했으나 적색에서 각각 주황색과 노란색으로 변화하였다. 온도가 증가함에 따라 색소 분해속도가 급격히 증가하였다. 많은 식품들이 약산성이므로 첨가물에 의한 안정성은 pH 5.0과 3.0에서 조사하였는데 무기이온들을 첨가하였을 때 큰 변화는 없었으나 $Al^{3+}$ 첨가 후에 농색화 현상과 함께 분해속도가 감소하여 안정화효과를 나타내었다. 빛에 의해(20,000 lux) 색소 분해가 촉진되어 대조구에 비해 2-3배 단축된 반감기를 나타내었다. 단당류와 이당류에 의해서는 변화가 거의 없었고 다당류를 첨가한 경우 약간의 안정화 효과가 관찰되었으며, 특히 CMC(carboxymethylcellulose)에 의해 pH 5.0의 조건에서 증가된 반감기를 나타내어 앞으로의 안정화 기술 개발의 가능성을 보여주었다.

• 한국식품과학회지
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• 제36권6호
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• pp.857-862
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• 2004

가열온도, 가열시간, presoaking 처리, 침지액 pH 처리, 저장 온도의 변화에 따라 아크릴아마이드 함량에 영향을 미치는 것을 확인하였다. 이를 식품생산에 적용하여 식품 내 아크릴아마이드 생성을 줄일 수 있는 방법을 도출할 수 있을 것으로 판단된다. 아크릴아마이드의 저감화는 원료 내 아크릴아마이드 형성가능물질을 줄임으로써 일차적으로 이루어질 수 있다. 본 실험을 통해 냉장보관한 감자의 아크릴아마이드 생성량은 보관기간이 길어질수록 증가하는 것을 확인할 수 있었다. 이는 감자의 환원당과 아미노산이 증가되어 아크릴아마이드 생성량이 증가되는 것으로 사료된다. 일반적으로 후렌치 후라이는 $160-180^{\circ}C$ 온도에서 2-5분간 가열한다. 아크릴아마이드 생성은 가열시간 및 온도에 크게 영향을 받으므로 이를 조절함으로써 식품 내 아크릴아마이드 함량을 줄일 수 있다. 아크릴아마이드는 $160^{\circ}C$ 이상의 고온에서 생성이 급속도록 증가되므로 식품을 조리 시 가열온도를 가능한 낮게 조절하는 방법도 아크릴아마이드 함량을 줄일 수 있을것으로 판단된다. $60^{\circ}C$의 증류수에 45분간 침지하였을 때 아크릴아마이드 생성량이 약 80% 감소되었으며 침지과정은 후렌치 후라이 제조시 제품의 색감을 좋게 하기 위해 제조과정 중 포함되어 있으므로 침지온도와 침지시간을 조절하는 것으로 아크릴아마이드 함량을 낮출 수 있을 것으로 판단된다.

• 복식문화연구
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• 제13권2호
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• pp.240-247
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• 2005

In this study, cotton fabric specimens were pre-mordanted using Sn, Al, Cu, Cr, and Fe, and subsequently dyed using cochineal, maintaining the pH of the dye bath constant using pH buffer solutions of 4, 5, 6, 7, and 8. In the cases of Al, Cr, and Sn mordanting, the dye-uptake was well accomplished in the acidic range of pH 4 and 5. However, the dye-uptake was not accomplished in the range over pH 6. In the cases of Cu and Fe mordanting, however, the pH value did not affect the dye-uptake and the dyeability in the alkaline range was not decreased remarkably. In the case of non-mordant, the dye-uptake was not accomplished at all, and the Cu and Fe mordanting gave rise to the best dyeability. In the cases of non-mordanting and Al, Cu mordanting, there was no change in the $\lambda_{max}$, and in the cases of Sn and Cr mordanting, the $\lambda_{max}$ moved toward the shorter wavelength. In the case of Fe mordanting only, the $\lambda_{max}$ moved gradually toward the longer wavelength, and due to the pH effect deep-dyeing effect was revealed.