• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(2)
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• pp.33-36
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• 2001

In this paper, we have studied the characteristics of wet etching using citric acid based wet etchant. We have used the citric acid / hydrogen peroxide solution, citric acid / hydrogen peroxide / D.I. water solution. From our experimental result, a volumetric 1：3 ratio of citric acid and hydrogen peroxide and 1 ： 3 ： 1 ratio of citric acid, hydrogen peroxide, and D.I. water is shown to be a better wet etchant of PHEMT's system.

• 한국균학회지
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• 제27권6호
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• pp.383-385
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• 1999

Cheese 제조시 부산물로 생성되는 whey를 배지로 사용하여 Aspergillus niger를 이용하여 citric acid를 생산하는데 영향을 미치는 여러 가지 요인 중 중요한 요인인 온도와 pH의 영향에 대하여 고찰하였다 15일간 27, 30, 33, $36^{\circ}C$와 pH 2, 3, 4, 5에서 각각 배양하면서 소비된 lactose의 양과 생산된 citric acid의 양을 측정하였다. 생산된 citric acid의 최대 농도는 33.9 g/l(구연산 생산에 쓰여진 유당을 기준으로 할 때 68.26%)이었으며, shaking speed는 citric acid 생산에 직접 영향을 주기보다는 pellet 형성시 그 형태에 영향을 미치는 것으로 나타났다. 배양 온도가 $33^{\circ}C$, pH는 3일때 가장 많은 양의 citric acid가 생산되었다.

• Journal of the Korean Wood Science and Technology
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• 제45권4호
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• pp.432-443
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• 2017

Maltodextrin and citric acid are two types of natural materials with the potential as an eco-friendly binder. Maltodextrin is a natural substance rich in hydroxyl groups and can form hydrogen bonds with lignoselulosic material, while citric acid is a polycarboxylic acid which can form an ester bond with a hydroxyl group at lignoselulosic material. The combination of maltodextrin and citric acid as a natural binder materials supposed to be increase the ester bonds formed within the particleboard. This research determined to investigate the bonding properties of a new adhesive composed of maltodextrin/citric acid for nipa frond particleboard. Maltodextrin and citric acid were dissolved in distillated water at the ratios of 100/0, 87.5/12.5, 75/25 and 0/100, and the concentration of the solution was adjusted to 50% for maltodextrin and 60% citric acid (wt%). This adhesive solution was sprayed onto the particles at 20% resin content based on the weight of oven dried particles. Particleboards with a size of $25{\times}25{\times}1cm$, a target density $800kg/m^3$ were prepared by hot-pressing at press temperatures of $180^{\circ}C$ or $200^{\circ}C$, a press time of 10 minute and board pressure 3.6 MPa. Physical and mechanical properties of particleboard were tested by a standard method (JIS A 5908). The results showed that added citric acid level in maltodextrin/citric acid composition and hot-pressing temperature had affected to the properties of particleboard. The optimum properties of the board were achieved at a pressing temperature of $180^{\circ}C$ and the addition of only 20% citric acid. The results also indicated that the peak intensity of C=O group increased and OH group decreased with the addition of citric acid and an increase in the pressing temperature, suggesting an interreaction between the hydroxyl groups from the lignocellulosic materials and carboxyl groups from citric acid to form the ester groups.

• Mycobiology
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• 제48권2호
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• pp.122-132
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• 2020

Citric acid is a commercially valuable organic acid widely used in food, pharmaceutical, and beverage industries. In this study, 260 yeast strains were isolated from soil, bread, juices, and fruits wastes and preliminarily screened using bromocresol green agar plates for their ability to produce organic acids. Overall, 251 yeast isolates showed positive results, with yellow halos surrounding the colonies. Citric acid production by 20 promising isolates was evaluated using both free and immobilized cell techniques. Results showed that citric acid production by immobilized cells (30-40 g/L) was greater than that of freely suspended cells (8-19 g/L). Of the 20 isolates, two (KKU-L42 and KKU-L53) were selected for further analysis based on their citric acid production levels. Immobilized KKU-L42 cells had a higher citric acid production rate (62.5%), while immobilized KKU-L53 cells showed an ~52.2% increase in citric acid production compared with free cells. The two isolates were accurately identified by amplification and sequence analysis of the 26S rRNA gene D1/D2 domain, with GenBank-based sequence comparison confirming that isolates KKU-L42 and KKU-L53 were Candida tropicalis and Pichia kluyveri, respectively. Several factors, including fermentation period, pH, temperature, and carbon and nitrogen source, were optimized for enhanced production of citric acid by both isolates. Maximum production was achieved at fermentation period of 5 days at pH 5.0 with glucose as a carbon source by both isolates. The optimum incubation temperature for citric acid production by C. tropicalis was 32 ℃, with NH₄Cl the best nitrogen source, while maximum citric acid by P. kluyveri was observed at 27 ℃ with (NH₄)₂ SO₄ as the nitrogen source. Citric acid production was maintained for about four repeated batches over a period of 20 days. Our results suggest that apple and banana wastes are potential sources of novel yeast strains; C. tropicalis and P. kluyveri which could be used for commercial citric acid production.

• 한국축산식품학회지
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• 제24권3호
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• pp.266-272
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• 2004

본 연구는 gelatin의 생산공정에서 각종 산 처리가 최종 gelatin의 품질에 어떤 영향을 주는지를 평가함으로써 양질의 gelatin을 생산하는데 기초를 제공하고자 하였다. Gelatin gel의 물성은 lactic acid로 처리한 gelatin이 높은 hardness, cohesiveness, brittleness를 나타내었고 다음으로는 citric acid, acetic acid 순으로 나타났다. Gelatin의 색도는 citric acid, 처리한 gelatin이 acetic acid나 lactic acid로 산침한 젤라틴 보다 높은 명도를 나타냈다. a-value는 acetic acid로 산침한 gelatin이 가장 높게 나타났으며 황색도를 나타내는 b-value는 lactic > acetic acid > citric acid 순으로 높게 나타났다. Gelatin의 점도를 측정한 결과 전단속도(shear rate)에 대한 전단응력(shear stress)의 관계는 모두 전단속도가 증가함에 따라 전단응력이 증가하는Newton성 유체로 판단되었다. 그 기울기는 acetic acid로 산침한 것이 가장 높게 나타났으며 lactic acid, citric acid 순으로 높게 나타났다. Gelatin내의 hydroxyproline 함량을 살펴보면 acetic acid(0.186 g/100 g sample)로 가장 높은 수치를 나타나며 다음으로 lactic acid, citric acid 순으로 나타났다. 그러나, sample중 crude protein 함량을 비교하면 acetic acid(68.74%), lactic acid(80.08%), citric acid(85.47%)로 나타났다. 이것은 gelatin의 열수 추출시 가장 작게 용출된 acetic acid가 가장 높은 collagenous connective tissue 함량(1.35 g/100g)을 나타내었다.

• 한국식품과학회지
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• 제29권3호
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• pp.588-594
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• 1997

제주산 온주밀감(Citrus unshiu)을 이용한 양조주를 제조하는데 적합한 효모를 선별하고, 밀감양조주의 품질에 직접적으로 연관된 효모의 citric acid 분해능에 대해서 기초조사를 실시하였다. 밀감양조주용으로 활용가능하다고 판단된 균주는 모두 11주이었다. 제주지역의 토양을 중심으로 5개의 효모균주를 분리, 선별하였는데, 그중 4개 주는 Saccharomyces cerevisiae, 나머지 1개 주는 S. ellipsoideus로 동정되었다. 한편 분양 균주 18주 중에서 선별된 균주는 6개 주로, S. cerevisiae 계통의 3개 주와 S. coreanus, S. uvarum, S. sake 각각 1개 주었다. 이중에서 S. cerevisiae 2개 균주의 citric acid 분해능을 조사하였다. Citric acid는 효모의 유일한 탄소원으로는 이용될 수 없었으나, citric acid가 glucose와 함께 탄소원으로 사용되었을 때, 배양액 중의 citric acid 농도는 감소하였으며, 정치배양 보다 진탕배양하였을 때 더 많이 감소하였다. 효모에 의한 citric acid의 이용은 ethanol 농도를 증가시키지 못하였으며, 오히려 citric acid는 효모의 생육을 부분적으로 저해하였다.

• Applied Biological Chemistry
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• 제40권2호
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• pp.123-127
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• 1997

다진 생강의 저장성을 향상시키고자 다진 생강에 citric acid $0.5{\sim}2.0%$처리는 초기 pH $3.1{\sim}4.6$으로 8개월 후에도 대체로 양호하였으며, citric acid 0.5% 처리의 polyphenol oxidase (PPO) 활성은 NaCl 5.0%나 ascorbic acid 0.5%처리보다 낮았고 항산화제인 ascorbic acid는 citric acid에 비하여 쉽게 변질되었다. NaCl(5.0%)+citric acid(0.5%)나 NaCl(5.0%)+citric acid(1.0%)의 혼합처리로 NaCl 5.0% 단일처리에 비하여 pH 및 PPO활성이 낮아 졌으며 12개월 경과 후에도 양호하였고, NaCl(5.0%)+ascorbic acid(0.5%)처리는 NaCl(5.0%)+citric acid(0.5%)처리와 비교하여 pH에는 큰 차이가 없었으며 4개월째 PPO활성이 급격히 증가하여 무처리보다도 높았으나 변질되지 않았다. 또한 NaCl+citric acid+ascorbic acid의 세 가지 혼합처리 중 5.0%+0.1%+0.1%, 5.0%+0.25%+0.1%, 5.0%+0.5%+0.1% 등의 처리는 8개월 저장시까지 대체로 양호하였으나 그 이후에는 변색이나 이취가 발생되어 장기보존에는 5.0%+0.5%+0.25%처리가 보다 효과적 이었다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2000년도 창립총회 및 춘계학술발표회
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• pp.133-136
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• 2000

Soil decontamination process was conducted to study adsorption and modeling characteristic of Sr$^{2+}$ ion using citric acid and water system with TRIGA soil. When the concentration of citric acid was increased, the BTC of Sr$^{2+}$ ion was to be closed to the BTC of $^3$$H_2O$ at experiments of soil adsorption. Beside, when the concentration of citric acid was under 0.01M Sr$^{2+}$ ion, BTLs was asymmetry. It was characteristic of nonequilibrium adsorption. R and $K_{p}$ , were decreased to be increased the concentration of citric acid. Asymmetry modeling was nearly the same to be compare with symmetry modeling in decontamination process, when the concentration of citric acid was decreased. Result of experiment was agree with asymmetry and symmetry model, when the concentration of citric acid was increased.eased.

• Journal of Ginseng Research
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• 제33권3호
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• pp.194-198
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• 2009

본 연구에서는 수삼을 식품에 쓰이는 산화 방지제인 ascorbic acid와 citric acid로 처리하여 홍삼을 제조한 후 활성성분인 페놀화합물과 진세노사이드의 추출물내 함량 변화를 HPLC를 이용하여 살펴보았다. 분석결과 citric acid 처리 홍삼에서 esculetin과 quercetin 함량이 무처리 홍삼에 비하여 각각 3.5 배, 2.0 배 증가하였고 ginsenoside 함량 역시 citric acid 처리시의 Rg$_3$, Rd, Rh$_2$ 증가량이 ascobic acid 처리시에 비하여 높았다. 따라서 인삼추출물의 이들 특정활성성분 강화를 위하여는 citric acid 처리가 효과적인 것으로 판단된다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제21권6호
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• pp.146-155
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• 2016

The field feasibility tests for a phytoextraction process were performed to identify the effect of citric acid as a chelate on the uranium (U) transfer into the plant for the naturally U contaminated soil in Duckpyeongri, Korea. For the feasibility tests, lettuce and Chinese cabbage were cultivated for 49 days on four testing grounds ($1m{\times}1m{\times}0.5m$ in each) in 2016. The citric acid solution was added to two testing grounds (one for lettuce and the other for Chinese cabbage) increasing the U transfer in two crop plants and their results were compared to those without the citric acid solution. When without the citric acid solution, the U concentration of plant after the cultivation was low (< $45{\mu}g/kg$ for leaves and < $450{\mu}g/kg$ for roots). However, with the addition of 50 mM citric acid solution, the U concentration of lettuce leaves and roots increased by 24 times and 1.8 times, and the U concentration of Chinese cabbage leaves and roots increased by 86.7 times and 5.4 times. The absolute accumulated U amount (${\mu}g$) in lettuce and Chinese cabbage also increased by 8.7 times and 50 times, compared to those without citric acid solution. Less than 8% of the U amount of exchangeable/carbonate phases was removed by using the lettuce and Chinese cabbage when the citric acid solution was not applied. However 52% and 66% of the U amount in exchangeable/carbonate phases were removed by the lettuce and the Chinese cabbage when the citric acid solution was added. The effect of the citric acid on the U transfer capability into the plants was quantitatively investigated by the field feasibility test, suggesting that U existing as exchangeable/carbonate phase in soil can be successfully removed by the phytoextraction process using Chinese cabbage with citric acid.