• Corrosion Science and Technology
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• v.20 no.3
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• pp.129-142
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• 2021

Effects of corrosion inhibitors (i.e., sodium nitrite, sodium hexametaphosphate, trimethylamine (TEA), sugar, and urea) on the corrosion resistance of carbon steel in CaCl₂ solution were investigated. The test solution was designed with response surface methodology of design of experiments (DOE) in the range of 0 ~ 50 ppm for NaNO₂, 0 ~ 200 ppm for (NaPO₃)₆, 0 ~ 2000 ppm for TEA, 0 ~ 3000 ppm for sugar, 0 ~ 200 ppm for urea with 3 wt% CaCl₂. The corrosion potential and the corrosion rate were measured with potentiodynamic polarization tests and analyzed statistically to find main effects of inhibitor concentrations and interactions between them. As a result, hexametaphosphate was the most effective compound in reducing the corrosion rate. Sugar also reduced the corrosion rate significantly possibly because it covered the surface effectively with a high molecular weight. The inhibiting action of sugar was found to be enhanced by adding trimethylamine into the solution. Nevertheless, trimethylamine did not appear to be effective in inhibiting corrosion by itself. However, urea and sodium nitrite showed almost no inhibition on corrosion resistance of steel.

• Journal of the Korean Society of Food Science and Nutrition
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• v.28 no.1
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• pp.33-39
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• 1999

Traditional kakdugi prepared from salted radish by the addition of fermented shrimp or anchovy sauce along with seasonings and spices, e.g., red pepper powder, garlic or ginger, which has been examined for the formation of volatile nitrosamine(NA) during its fermentation at 5oC and 17oC. Changes of acidity were increased; while, those of ascorbic acid and pH were continually de creased and besides concentrations of salt were scarcely observed during the fermentation of kakdugi at 5oC and 17oC. High initial levels of nitrate in radish followed by a gradual decreased in nitrate concentration, along with increasing levels of nitrite, during its fermentation. During the fermentation of kakdugi, NA such as N nitrosodimethylamine(NDMA) and N nitrosodiethylamine(NDEA) was identified; these NA in kakdugi that had been prepared with shrimp sauce contained in the higher levels than kimchi that had been prepared with anchovy sauce, and both NDMA and NDEA were detected higher levels in the fermented sample at 17oC than in the fermented sample at 5oC. In kakdugi, NDMA and NDEA levels were continually increased during its fermentation; its levels after 35 days fermentation at 17oC were 0.5~16.7 and 0~5.2 g/kg in added shrimp sauce sample, 0. 5~8.7 and 0~4.7 g/kg in added anchovy sauce sample and 0.4~4.8 and 0~2.4 g/kg in control, respectively. The occurrence of NA such as NDMA and NDEA appeared to arise from the fermented sauce and radish used in preparation of the kimchi.

• Preventive Nutrition and Food Science
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• v.6 no.3
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• pp.142-146
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• 2001

This study was performed to investigate chemical and functional properties of Glechoma hederacea leaves in respect to its potential use as food material or as a medicinal herb. The chemical compositions on a dry harris were 20.38% in protein, 3.96% in fat, 59.58% in carbohydrate, 15.78% in ash, 5.36% in reducing sugar, 14.11% in total sugar and 0.26% in polyphenol, respectively. The free sugars were mainly comprised of glucose, fructose and sucrose. In fatty acids compositiosn, linolenic acid showed the highest concentration at 45%, while the ratios of saturated to unsaturated fatty acids were 1 : 1.91. Seventeen kinds of total amino acids were determined, with the highest concentration (2,465.71 mg%) of glutamic acid. Among the free amino acids, praline showed the highest concentration (260.09 mg%), followed by glutamine, $\alpha$ -amino adipic acid, glutamic acid and valine. The contents of major minerals were 647.32 mg% in Na, 597.53 mg% in K and 239.75 mg% in Ca. The antioxidative activity of 10% water extract was similar to that of 50 ppm tocopherol. The nitrite scavenging ability reached the highest bevel at pH 1.2 and the lowest at pH 6.0.

• Corrosion Science and Technology
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• v.16 no.3
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• pp.91-99
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• 2017

The objective of this work was to develop efficient synergistic inhibitor combinations comprising sodium nitrite ($NaNO_2$) and an inhibitor-blend code named (SN-50), keeping in view of their application in industrial cooling water systems. The electrochemical characteristics of the carbon steel working electrode in simulated cooling water (SCW), without and with the addition of different combinations of the inhibitors, were investigated using electrochemical impedance spectroscopy (EIS), open circuit potential (OCP). The electrode surface changes were followed by visual characterization methods. It was demonstrated in this study that all the combinations of the inhibitors exhibited synergistic benefit and higher inhibition efficiencies than did either of the individual inhibitors. The addition of SN-50 inhibitor to the SCW shifted the OCP to more anodic values and increased the polarization resistance ($R_p$) values of carbon steel at all applied concentrations. The higher the applied sodium nitrite concentration (in the protection concentration range), the higher the obtained $R_p$ values and the inhibition efficiency improved by increasing the inhibitor concentration.

• Journal of Korean Society on Water Environment
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• v.18 no.2
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• pp.113-122
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• 2002

A bench-scale anoxic membrane bioreactor (MBR) system, consisting of a bioreactor coupled to a ceramic crossflow ultrafiltration module, was evaluated to treat a synthetic wastewater containing alkaline hydrolysis byproducts (hydrolysates) of RDX, The wastewater was formulated the same as RDX hydrolysates, and consisted of acetate, formate, formaldehyde as carbon sources and nitrite, nitrate as electron accepters. The MBR system removed 80 to 90% of these carbon sources, and approximately 90% of the stoichiometric amount of nitrate, 60% of nitrite. The reactor was also operated over a range of transmembrane pressures, temperatures, suspended solids concentration, and organic loading rate in order to maximize treatment efficiency and permeate flux. Increasing transmembrane pressure and temperature did not improve membrane flux significantly. Increasing biomass concentration in the bioreactor decreased the permeate flux significantly. The maximum volumetric organic loading rate was $0.72kg\;COD/m^3/day$, and the maximum F/M ratio was 0.50 kg N/kg MLSS/day and 1.82 kg COD/kg MLSS/day. Membrane permeate was clear and essentially free of bacteria, as indicated by heterotrophic plate count. Permeate flux ranged between 0.15 and $2.0m^3/m^2/day$ and was maintained by routine backwashing every 3 to 4 day. Backwashing with 2% NaOCl solution every fourth or fifth backwashing cycle was able to restore membrane flux to its original value.

• Journal of the Korean Society of Food Science and Nutrition
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• v.17 no.2
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• pp.125-135
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• 1988

In recent years, the presence of N-nitrosamine, which was produced by the interaction of nitrite and secondary amine, in the fermented foods has been the subject of considerable interest and controversy. In this experiment, the levels of N-nitrosamine such as N-nitrosodimethylamine(NDMA), N-nitrosodiethylamine(NDEA) and N-nitrosodipropylamine(NDPA) in the Korean ordinary soysauce, which were added with ascorbic acid, sorbic acid, and sodium benzoate in the making of it were analyzed by low resolution mass spectrometry, and then the changes of dimethylamine(DMA), nitrate and nitrite nitrogen during the fermentation of it were observed. The contents of DMA nitrogen increased during the fermentation of Korean ordinary soysauce, continuously, but those of DMA nitrogen in the soysauce which had been added with ascorbic acid were inhibited, considerably, until the fermentation of 70days. The levels of nitrate nitrogen during the fermentation of Korean ordinary soysauee decreased, while those of nitrite nitrogen increased. The soysauce which had been incoporated with ascorbic acid in the making of it showed low amounts of nitrite. The concentration of NDMA in the control sample were 2.7 and $8.5{\mu}g/kg$ after the fermentation of 30 and 60 days, respectively, those of NDMA increased during the fermentation of Korean ordinary soysauce, but NDEA and NDPA in all of the soysauce were not detected. The samples were treated with ascorbic acid, sorbic acid, and sodium benzoate in the making of Korean ordinary soysauce were turn out to be effective in preventing the formation of NDMA. Inhibitive actions from food additives as above were, respectively, $82.2{\sim}87.0%$(ascorbic acid), $25.9{\sim}65.4%$(sorbic acid) an $13.2{\sim}63.5%$ (sodium benzoate) in comparison with control sample during the fermentation of Korean ordinary soysauce. NDMA contents were detected below $1.5{\mu}g/kg$ in the soysauce, which food additives were mixed to the pure NaCI in the brewing of it. Free amino acids such as glutamic acid, proline, and histidine were proved to be inhibiting the formation of NDMA during the fermentation of Korean ordinary soysauce. This might be due to the reaction above amino acids and nitrite by Van Slyke reaction.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.3
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• pp.378-383
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• 2002

The aim of the study was to analyze N-nitrosamine (NA) and its precursors in serveral fermented foods which were treated with nitrite, thiocyanate and ascorbic acid under simulated gastric digestion. Every analyzed sample contained nitrate, with levels ranging from 0.3 to 1.3 mg/kg, but nitrite was present at very low levels of less than 0.3 mg/kg. And other precursors of amines such as dimethylamine and trimethylamine were detected less than 0.5 mg/kg in every samples. N-nitrosodimethylamine (NDMA) was detected in the levels of <0.5 ∼ 2.7 ug/kg in soy sauce,1.5∼3.1 ug/kg in soybean paste and <0.5∼1.8 ug/kg in beer, while NDMA levels increased by 1.1∼4.5 times in the fermented foods which were digested under simulated gastric conditions.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.5
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• pp.463-468
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• 1987

The present paper was investigated to elucidate the nitrite-scavenging ability of vegetable extracts. Vegetable extracts possessed the scavenging ability of nitrite. By fractionatioh of vegetable extracts,nitrite-scavenging ability of garlic (Allitum sativum for. Pekinense), chinese pepper (Zanthexylum schinifolium), onion (Allium cepa), welsh onion (Allium fistulosum) and ginger (Zingiber officinale) extracts were effective in the water-soluble fraction, but carrot (Daucus carota uar. sativa) in the methanol-soluble fraction. Nitrite-scavenging ability of vegetable extracts was also pH-dependent, highest at pH 1.2 and lowest at pH 6.0. Particularly, nitrite-scavenging abilities of water-soluble fractions obtained from garlic and chinese pepper were similar to that of L-ascorbic acid at pH 1.2. After vegetable extracts were treated with sodium borohydride, nitrite-scavenging ability was remarkably decreased at pH 1.2. It is assumed that reducing powers of vegetable extracts participated in their nitritescavenging abilities.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.590-593
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• 2001

The effect of salinity on the nitrification efficiency of the nitrifier consortium was evaluated for the nitrification of saline wastewater. The nitrifier consortium, which was the activated sludge acclimated with ammonium as the only energy source, was used as the nitrifier for the salt acclimation. Airlift reactors for the nitrification of ammonia with increasing concentration in saline synthetic wastewater (35 g/I NaCD, and synthetic wastewater without salt as a control, were continuously operated with the nitrifier consortium for 43 days. The ammonia removal rate was about 23g ammonia-N/$m^3$/day in both the absence and presence of the salt. An accumulation of nitrite was observed in the saline nitrification reactor at an early period. However, the nitrite decreased to less than 1 mg/l after 39 days of operation. The salinity increased the acclimation time of the nitrifier consortium to obtain a stable marine nitrification system. However, the salt acclimated system showed the efficient removal of ammonia which was same as that without salt.

• Journal of Nutrition and Health
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• v.7 no.4
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• pp.21-23
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• 1974

Nitrite, one of the precursors of dimethylnitrosamine distributes widely in natural foods and also used as a color fixative in meat products. In this paper Nitrites and Nitrates contents in Korean-Kimchi and Human Saliva were as follows. (1) pH: $pH:\;3.8{\sim}5.8$(in Korean-Kimchi soup) (2) NaCl: $1.5{\sim}3.1%$(in Korean-Kimchi soup) (3) Acidity: $0.38{\sim}0.62%$(in Korean-Kimchi soup) (4) $NO_2-$ $0.25{\sim}0.68ppm$ (in Korean-Kimchi) $1.9{\sim}5.0ppm$ (in Human Saliva) (5) $NO_3-$ $35.0{\sim}92.0ppm$ (in Korean-Kimchi) $7.6{\sim}28.0ppm$ (in Human Saliva) These results showed low contents in Korean-Kimchi and Human Saliva.