여러 회절광의 세기를 비슷하게 분배하는 회절격자의 제작

홍동리,차명식 한국물리학회 2007 새물리 Vol.54 No.3

A balanced or equal beam splitter is necessary in several optical experiments, such as complicated multi-beam pump-probe spectroscopy. We fabricated photoresist surface-relief gratings with different duty cycles in order to achieve relatively balanced intensities among the diffraction orders. A grating with a duty cycle of 1:3 gave relatively balanced beam splitting among the $\pm$0, $\pm$1, and $\pm$2 orders without significantly sacrificing the total diffraction efficiency. 한 개의 빔을 여러 개의 균일한 빔으로 나누는 beam 분배기는 복잡한 multi-beam pump-probe 분광학 실험 등의 광학 실험에 필요하다. 우리는 회절 차수들의 세기가 상대적으로 균일하게 나오게 하기 위해서 각각 다른 duty비로 photoresist 표면 위상 회절격자를 만들었다. Duty비 1:3의 회절격자는 전체 회절효율에 있어서 큰 손실 없이 $\pm$0, $\pm$1, $\pm$2차 회절광들의 세기를 비교적 균일하게 분배했다.

반응표면분석법을 이용한 Trimethylamine의 Static과 Dynamic Headspace 분석 방법 최적화

홍동리,조성래,유정완,김소현,김현재,이양봉 한국식품영양과학회 2019 한국식품영양과학회지 Vol.48 No.7

본 연구에서는 생선 비린내의 주요 성분 중 하나인 trimethylamine 분석방법을 반응표면분석법을 사용하여 최적의 분석 조건을 설계하였다. Sodium hydroxide를 통해 headspace에서의 직접 분석과 SPME를 이용한 두 가지 방안을 제시하였으며, sodium hydroxide의 농도가 TMA를 headspace에 휘발시키는 데 중요한 요인으로서 분석에 필수 요소인 것을 알 수 있었으며, 온도와 시간 또한 어느 정도 영향을 주는 요인으로 판단된다. 추후 본 연구를 통해 신선도를 평가하는 TMA 분석에 신뢰도 높은 결과를 활용할 수 있을 것으로 판단된다. Trimethylamine (TMA) is an index compound of fish smell in fishery products. The objective of this study is to optimize the static and dynamic headspace analyses with 200 μL direct injection and solid phase microextraction using response surface methodology. A fractional 4-level-3-factor experiment design which consists of 33 experimental trials and five replicates at nine center points was adopted to see the effect of independent values such as TMA concentration (2∼14 mg/100 g), sodium hydroxide concentration (5∼25%), temperature (4∼32°C), and time (3∼11 min) on the responses of isolated TMA amounts. Data were analyzed using SAS Statistical Software to get a second-order polynomial formula and the 3-dimensional graphs were drawn with Design-Expert Software. Regression coefficients (R2) of direct injection and solid phase microextraction were 0.9816 and 0.9802, respectively. TMA contents between static and dynamic analyses showed a similar tendency. These results will provide basic information in measuring TMA contents in fish products.

Identification of Headspace Volatile Compounds of Blended Coffee and Application to Principal Component Analysis

김현재,홍동리,유정완,이승민,이양봉 한국식품영양과학회 2019 Preventive Nutrition and Food Science Vol.24 No.2

Coffee can be blended to create a variety of products to meet consumer’s needs. In order to uncover the blending effect of coffee beans, we performed an experiment using principal component analysis (PCA). Twelve varieties of green beans were tested in 11 experimental groups, and the volatile compounds of the beans were analyzed. A total of 41 volatile compounds were identified. PCA was performed on 13 compounds that had a low odor threshold value or a high concentration among the identified compounds. PCA of total volatile compounds showed that principal component (PC) 1 and PC2 were extracted within 80% cumulative dispersion level. In PC1 and PC2, furfuryl alcohol and formic acid ethyl ester showed the greatest positive correlation coefficients among all the volatile compounds. The largest negative correlation coefficients in PC1 and PC2 were 4-hydroxy-2-butanone and 3-(ethylthio)propanal, respectively. Using PCA of the major volatile compounds in coffee, propanal and 1-methylpyrrole were found to have the largest positive correlation coefficients in PC1 and PC2, respectively. In the score plot of the major volatile components, 4 kinds of blended coffee were closely grouped, therefore showing similar aroma qualities. However, 5 kinds of other blended coffees showed a positive correlation with PC2. This is probably due to 3-(ethylthio)propanal acting as a specific value. The application of statistical methods to blended coffee allows for logical and systematic data analysis of data and may be used as a basis for quality evaluation.

빙과류의 품목별 제품의 미생물학적 안전성 평가

유정완,김소현,홍동리,김현재,정은주,이재화,양지영,이양봉 한국식품위생안전성학회 2019 한국식품위생안전성학회지 Vol.34 No.4

In order to evaluate the microbiological safety of ice cream products, the total viable bacterial counts were measured in 6 kinds of ice pops, 5 kinds of non-milk fat ice cream, and 5 kinds of milk fat ice cream, sold in local markets. In addition, E. coli, S. aureus, B. cereus, and L. monocytogenes were artificially inoculated in three types of ice cream products and stored at -5 o C, -10 o C, and -18 o C, respectively, and after inoculation, viable cells were measured periodically. As a result of the total viable count, about 1~2 log CFU/mL was detected in 16 kinds of ice cream products. As a result of inoculation with microorganisms at various temperatures, the number of viable cells decreased as the storage period became longer, and the higher the storage temperature, the faster the microorganisms died. Especially, the microorganisms were killed faster in the ice pop products than in the other ice cream products, and the microorganisms were killed relatively slower in the milk ice cream. L. monocytogenes and S. aureus were relatively stable in frozen conditions compared to other microorganisms. The microbial contamination of commercial ice cream was lower than the allowable standard of the Korean Food Code. Microorganisms did not proliferate when the microorganism was inoculated at freezing temperature. Therefore, it is expected that the microbiological safety of frozen foods will be ensured if the sanitary control and disinfection of raw materials are thoroughly carried out during the production of frozen confections and the temperature control during distribution and storage is well maintained.

Quality assessment and acceptability of whiteleg shrimp (Litopenaeus vannamei) using biochemical parameters

So-Hyun Kim,Eun-Ju Jung,홍동리,Seung-Eun Lee,이양봉,조승목,김선봉 한국수산과학회 2020 Fisheries and Aquatic Sciences Vol.23 No.3

Background: This study aimed to provide a basic standard for assessing freshness and acceptability of whiteleg shrimp (Litopenaeus vannamei). Methods: It was divided into whole body and meat and stored at 25 °C to evaluate both quality and freshness changes that occur over time. The shelf life of shrimp was estimated as 17 and 20 h for whole body and meat, respectively. Results: In chemical analysis, K-value increased from 9.96 to 12.32% to a maximum of 75.14%, and TVB-N increased from 1.86 mg/100 g to 34.71 mg/100 g. For volatile sulfur compounds, methyl mercaptan and dimethyl disulfide increased from 0.00 mg/100 g to 1.10 mg/100 g and 1.26 mg/100 g, respectively, rapidly increasing with decreasing freshness. Conclusion: Changes in all biochemical indicators significantly correlated with the sensory evaluation results. This study contributes to the knowledge about whiteleg shrimp spoilage and freshness, providing a basis for developing methods to improve shrimp quality control and management.

발효식품에서 분리된 Saccharomyces cerevisiae를 이용한 Trimethylamine 저감화

박슬기,이재화,조두민,강민균,장유미,조연진,홍동리,김영목 한국수산과학회 2019 한국수산과학회지 Vol.52 No.2

Trimethylamine (TMA) is a nitrogen-based aliphatic organic compound. It is a major odorous component of fish and fishery products and is often used as an indicator of fish quality. The efficacy of TMA removal by various yeast strains was investigated. The five yeast strains found to be most effective in removing TMA were isolated from fermented foods and were identified as Saccharomyces cerevisiae based on biochemical and 18S rRNA sequence analyses. These strains were designated as S. cerevisiae SK1511, SK1512, SK1513, SK1514 and SK1515. Yeast cultures were treated with a TMA solution (0.3%, v/v), and the level of TMA reduction was analyzed by headspace gas chromatography. The five S. cerevisiae strains removed 32.02-50.34% of the TMA from the solution. This study is the first to demonstrate TMA reduction by microbial treatment.