Sungkyun Kim

Honolulu University, Honolulu, Hawaii, United States

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Publications (3)3.01 Total impact

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    ABSTRACT: The contents of trans fatty acids in French fries served at the local food service retailers in Honolulu were determined by simple Fourier transform infrared (FTIR) spectroscopic technique without the pretreatment of fatty acid extraction. A horizontal attenuated total reflection (ATR) crystal made of zinc selenide (ZnSe) was used to obtain FTIR spectra of French fries with and without fatty acid extraction. Residual oil films obtained by pressing French fries directly on the ATR crystal surface without removal of any solid particles or air bubbles were scanned for the spectral measurement. The calibration set consisted of triolein (C18:1, 9-cis) and trielaidin (C18:1, 9-trans) mixed in varying ratios. All spectral data were averaged and converted into GRAMS format. The peak heights of each spectrum at 966 cm−1 were found to be linearly correlated with the contents of trans fatty acids in the validation set (n = 8, R2 = 0.9835). The developed calibration model was validated by comparing the results obtained from the ATR-FTIR with Mojonnier extraction and gas chromatography–mass spectrometry (GC–MS).
    Food Chemistry. 01/2011;
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    ABSTRACT: A rapid immunofluorescence method for foodborne pathogens in food systems using microwire sensor coupled with high frequency alternating current was developed. The method was intended to enrich and quantify E. coli cells internalized in baby spinach leaves. The targeted bacterial cells in the sample solution were captured on microwires in a diameter of 25μm, and were bound to fluorescein isothiocyanate (FITC) labeled polyclonal E. coli antibodies. Fluorescent images of the FITC antibodies were obtained using a fluorescence microscope equipped with a charge-coupled-device (CCD) camera, and the fluorescent intensity (FI) was quantified through image processing. The capture of E. coli K-12 in PBS buffer was optimized when the electric field was generated at the frequency of 3MHz and 20Vpp with bacterial concentration of 107CFU/mL. The detection limit of our sensing device was determined to be 103CFU/mL. Field emission scanning electron microscopy (FESEM) was used to validate and visualize E. coli cells captured on the tip surface. The sensitivity and specificity of the developed sensor has been successfully validated by testing E. coli internalized in baby spinach leaves. The immunofluorescence detection has been completed within 15min. Moreover, it was found that the enrichment process of E. coli cells using the dielectrophoretic force was rarely affected by food particles, which proved the sensing selectivity. The developed sensor is expected to meet the steady demand for a simple, rapid, highly sensitive detection approach to quantify the targeted microbes in food systems.
    Innovative Food Science & Emerging Technologies - INNOV FOOD SCI EMERG TECHNOL. 01/2011; 12(4):617-622.
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    ABSTRACT: Bacterial contamination continues to be a serious concern for food safety. Although washing fresh produce helps in reducing pathogen levels, pathogen internalization often limits the effectiveness of washing. When pathogens internalize in leafy vegetables, the method of identification and quantitative measurement would be called into question. This study was aimed to use Fourier Transform Infrared (FTIR) spectroscopy integrated with an attenuated total reflectance kit for quantification of Escherichia coli K-12 internalized in baby spinach. The bacteria were inoculated into vascular and intracellar tissues of spinach leaves by syringe injection and the distribution of internalized E. coli K-12 cells was confirmed under scanning electron microscopy (SEM). FTIR measurement following the preparation of bacterial suspension from spinach leaves with high speed pulverizing enabled to detect the absorbance peaks in the amide II region between 1590 and 1490 cm⁻¹ as a fingerprint for the microbes. It was found that the estimated concentrations of E. coli K-12 agreed well with the concentrations determined by plate counting with R² values of 0.98 and 0.97 in peptone water and spinach extracts, respectively. The results demonstrated that FTIR can identify and quantify E. coli K-12 in baby spinach extracts at a limit of detection of approximately 100 CFU/mL in 5 min. The developed method is expected to be suitable for the analysis of pathogenic E. coli strains and other bacterial species in fresh vegetables.
    International journal of food microbiology 10/2010; 144(1):147-51. · 3.01 Impact Factor

Publication Stats

3 Citations
3.01 Total Impact Points

Institutions

  • 2011
    • Honolulu University
      Honolulu, Hawaii, United States
  • 2010
    • University of Hawaiʻi at Mānoa
      • Department of Molecular Biosciences and Bioengineering
      Honolulu, HI, United States