Yang-Bong Lee

Characterization of oil including astaxanthin extracted from krill (Euphausia superba) using supercritical carbon dioxide and organic solvent as comparative method

Krill oil including astaxanthin was extracted using supercritical CO2 and hexane. The effects of different parameters such as pressure (15 to 25MPa), temperature (35 to 45 °C), and extraction time, were investigated. The flow rate of CO2 (22 gmin−1) was constant for the entire extraction period of 2.5 h. The maximum oil yield was found at higher extraction temperature and pressure. The oil obtained by SC-CO2 extraction contained a high percentage of polyunsaturated fatty acids, especially EPA and DHA. The acidity and peroxide value of krill oil obtained by SC-CO2 extraction were lower than that of the oil obtained by hexane. The SC-CO2 extracted oil showed more stability than the oil obtained by hexane extraction. The amount of astaxanthin in krill oil was determined by HPLC and compared at different extraction conditions. The maximum yield of astaxanthin was found in krill oil extracted at 25 MPa and 45 °C.

Removal of off-flavors from sea tangle (Laminaria japonica) extract by fermentation with Aspergillus oryzae.

This study was conducted to reduce off-flavors from sea tangle (Laminaria japonica) extract since the typical odor of seaweed is an impediment to consumption of seaweed products. Fifty-six odor compounds emitted from the extract were identified using a thermal desorbor and gas chromatography-mass spectrometry. On the basis of expected odor intensity (EOI), isovaleric acid (41.2%), allyl isothiocyanate (22.6%), octanal (11.1%) and acetaldehyde (10.6%) were responsible for about 85.5% of total odor strength in the extract, suggesting that the odor of the extract might mainly be attributed to these compounds. The EOIs of odor compounds were dramatically reduced or disappeared during fermentation by Aspergillus oryzae. Total EOI of the odor compounds decreased about four-fold, compared with that of the raw extract (control) after the four days of fermentation at 30°C with agitation at 120 rpm. These results indicate that microbial fermentation may be a good strategy to reduce off-flavors of seaweeds.

Headspace Volatile Compounds of Steamed Liriopis Tuber Tea Affected by Steaming Frequency

Flavor quality of Liriopis tuber tea that was made using a steaming process was studied by measuring changes in headspace volatile compounds. Headspace volatile compounds of the prepared samples were isolated, separated and identified by the combined system of purge & trap, automatic thermal desorber, gas chromatography, and mass selective detector. As steaming frequencies were increased, the area percent of aldehydes decreased from 32.01% to 3.39% at 1 and 9 steaming frequency times, respectively. However, furans and ketones increased from 18.67% to 33.86% and from 9.60% to 17.40% at 1 and 9 times, respectively. The savory flavor of Liriopis tuber tea was due to a decrease in aldehydes contributing a fresh flavor at the 1st steaming process and newly generated furans from nonenzymatic browning with repeated steaming frequencies. These results will provide basic information for quality control of the newly developed Liriopis tuber tea.

Chemometric Approach to Fatty Acid Profiles in Soybean Cultivars by Principal Component Analysis (PCA)

The purpose of this study was to investigate the fatty acid profiles in 18 soybean cultivars grown in Korea. A total of eleven fatty acids were identified in the sample set, which was comprised of myristic (C14:0), palmitic (C16:0), palmitoleic (C16:1, ω7), stearic (C18:0), oleic (C18:1, ω9), linoleic (C18:2, ω6), linolenic (C18:3, ω3), arachidic (C20:0), gondoic (C20:1, ω9), behenic (C22:0), and lignoceric (C24:0) acids by gas-liquid chromatography with flame ionization detector (GC-FID). Based on their color, yellow-, black-, brown-, and green-colored cultivars were denoted. Correlation coefficients (r) between the nine major fatty acids identified (two trace fatty acids, myristic and palmitoleic, were not included in the study) were generated and revealed an inverse association between oleic and linoleic acids (r=−0.94, p<0.05), while stearic acid was positively correlated to arachidic acid (r=0.72, p<0.05). Principal component analysis (PCA) of the fatty acid data yielded four significant principal components (PCs; i.e., eigenvalues>1), which together account for 81.49% of the total variance in the data set; with PC1 contributing 28.16% of the total. Eigen analysis of the correlation matrix loadings of the four significant PCs revealed that PC1 was mainly contributed to by oleic, linoleic, and gondoic acids, PC2 by stearic, linolenic and arachidic acids, PC3 by behenic and lignoceric acids, and PC4 by palmitic acid. The score plots generated between PC1-PC2 and PC3-PC4 segregated soybean cultivars based on fatty acid composition.

Production of value added materials by subcritical water hydrolysis from krill residues extracted by supercritical carbon dioxide

The aim of this study was the determination of the best experimental conditions for the production of useful materials such as amino acids by subcritical water hydrolysis from supercritical carbon dioxide extracted krill residues and to compare the results with raw krill. Subcritical water hydrolysis efficiency from raw and de-oiled krill was examined over the temperature range of 200 to 280°C, ratio of material to water for hydrolysis was 1:50 g/ml and for water sample contact equilibration times of 5 min to decrease the decomposition of amino acids. Nitrogen and air were used as atmosphere at pressure estimated to be between 0.101 and 6.41 MPa. The hydrolysis efficiencies of glycine, arginine, and leucine were found to be increased with increasing water temperature, consistent with higher solubility at higher temperatures. The highest yield of amino acids in de-oiled krill hydrolysate was at 280°C. While, the highest amino acid yield in raw krill hydrolysate was at low temperature 200°C. Also, reducing sugar content was analyzed in both samples and the results showed that the yield of reducing sugar in deoiled krill hydrolysate was higher than that of raw krill hydrolysate. Key words : Subcritical water hydrolysis, krill, amino acid, value added materials.

Monthly Variations in the Nutritional Composition of Antarctic Krill Euphausia superba

Abstract The proximate composition and various specific components of Antarctic krill Euphausia superba , in the catch season between March and August were investigated. Frozen krill were freeze-dried and milled. The proximate composition comprised water, proteins, fats, ash, fatty acids, and amino acids, while the specific components were vitamins, minerals, nucleotides, betaine, and astaxanthin. The moisture content of the krill ranged from 77 to 80%, with the highest value in June, and the ash content was be-tween 12 and 13%. The protein content was lowest in May, and the fat content was 18–19%, with the highest value in March. The amino acid content varied according to the season: taurine and glycine were highest in August; β-alanine was higher in April and May; and arginine, ornithine, and lysine were highest in March. The unsaturated fat content was ~50% and omega-3 fatty acids were highest in June. Oil-soluble vitamins A and E were highest in March, and the water-soluble vitamin content was less than that of oil-soluble vitamins. The mineral content was highest in June, and the most abundant mineral was sodium at 235.60 mg/100 g krill. The content of other minerals was lowest (2.94 mg/100 g) in April, except for lead. The nucleotide content was highest in July, while the betaine content was highest in April and lowest in June. The astaxanthin content was highest in May and ranged from 6 to 10 ppm in other months.

Isolation and Characterization of Nonylphenol-degrading Bacteria

To isolate a nonylphenol (NP)-degrading bacterium, we isolated a single colony from the NP-degrading microbial consortium SW-3, which was previously isolated from an aqueous environment. Ten colonies that exhibited different cell morphologies were isolated and the strains were named SW-3-A, -B, -C, -D, -E, -F1, -F2, -G, -H, and -I. The ability of isolates to degrade NP was evaluated by kinetic analysis by the constant of NP degradation rate (k1) and the half-life time of NP degradation (t1/2). SW-3-F1, -F2, -G, and -I strains were superior at degrading NP. The k1 and t1/2 values of the four strains were sixfold higher and one-sixth lower, respectively, than those of the consortium strain. Additionally, SW-3-F1, -G, and -I strains were tested for their ability to degrade NP during coculture. NP degradation by coculture with a combination of all three strains was inferior to that of culture conducted with single isolates, suggesting that the three strains are antagonistic toward each other during NP degradation.

Purification and deodorizing activity against methyl mercaptan of polyphenol oxidase from lettuce (Lactuca sativa L.)

Polyphenol oxidase (PPO) from lettuce was isolated to determine the effect of its involvement in deodorizing activity by measuring the reduction in the amount of methyl mercaptan. The enzyme and deodorizing activities of PPO from lettuce were evaluated using different substrates, temperatures, and pH levels. The molecular weight of purified PPO from lettuce was estimated to be 56 kDa. The PPO and deodorizing activities were highest at the pH range of 6.0 at 20 °C and 5.0 at 10 °C, respectively. The deodorizing and PPO activities were greater for ortho-diphenols than monophenols and polyphenol. Especially, (+)-catechin, one of ortho-diphenols was shown in 100% PPO activity, and chlorogenic acid and caffeic acid eliminated a methylmercaptan odor up to 95%. The deodorizing activity was highest in Cu2+ solution, but ascorbic acid and sodium hydrosulfite inhibited deodorizing activity. These basic data will provide an optimum manufacturing condition for commercial products using lettuce extracts.

Analysis of Headspace Volatile Compounds in Cold-stored and Freeze-dried Krill Eupausia superba

Abstract Headspace volatile compounds of cold-stored and freeze-dried Krill Eupausia superba were analyzed to investigate their flavor qualities using a system combining a dynamic headspace isolator, an automatic thermal desorber, and a gas chromatograph-mass-selective detector. Levels of oxidation products of polyunsaturated fatty acids such as aldehydes, alcohols, and ketones, which are known to give seafood a nasty smell because of their low flavor threshold values, increased during cold storage of krill. Notably, levels of 2-methylpropanal, 3-methylbutanal, 2-methylbutanal and 2-butanone increased during its storage. They can be considered index compounds of off-odor according to freshness degradation during storage. By contrast, in freeze-dried krill powder, levels of aldehydes, ketones, and aromatic compounds decreased rapidly. Only alcohols, which did not greatly affect the food flavor, were isolated in large amounts. It was confirmed that levels of oxidized compounds of krill increased during cold storage, but decreased in freeze-dried krill.

Food Quality of Patties Prepared Using Antarctic Krill Euphausia superba Meat

This study developed patties using the Antarctic krill Euphausia superba and investigated the food quality of the patties. Three different types of krill patty were produced: krill patties with added 1) corn oil (CKP), 2) AA grade surimi (AKP), and FA grade surimi (FKP). Their proximate composition, Hunter color value, texture, sensory evaluation, and levels of astaxanthin, cholesterol, calories, total amino acids, fatty acids, and fluoride were investigated. The moisture and crude protein contents were highest in FKP. The calorie and astaxanthin contents were highest in CKP and lowest in AKP. The cholesterol content was highest in CKP and lowest in AKP. Measuring the Hunter color value of cross-sections of the patties, the L values were highest for FKP, and the a and b values highest for AKP. The total amino acids were highest in FKP and lowest in CKP. The major fatty acids were highest in FKP. The hardness and chewiness were highest in FKP and lowest in CKP. The fluoride content was highest in AKP and lowest in FKP. The sensory evaluation had the highest scores for FKP and lowest for CKP. Accordingly, FKP appears to have better food quality than the other two products.