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Cheigh, Hong-Sik,Um, Soo-Hyoun,Lee, Chang Y. 부산대학교 유전공학연구소 1995 분자생물학 연구보 Vol.11 No.-
Antioxidant activity of melanin related products obtained from enzymatic oxidation of catechin was studied from the catechin-polyphenol oxidase reaction at pH 6.5 and 25℃ at various time intervals. All catechin-enzyme reaction products (CERPs) were brown in varied intensities with increased absorption at 210-220, 380-390nm, and 420-430 nm. CERPs obtained at the early stage of the reaction showed a higher antioxidant activity than those from the later stage. Antioxidant activity of CERPs may be explained by their abilities of hydrogen atom donation, free radical scavenging, and lipoxygenase inhibition. However, the exact mechanism of the antioxidant activity of CERPs cannot be explained until their chemical structures are elucidated.
Cheigh, Chan-Ick,Park, Mi-Hyun,Chung, Myong-Soo,Shin, Jung-Kue,Park, Young-Seo Elsevier 2012 Food Control Vol.25 No.2
<P><B>Abstract</B></P><P>The purpose of this study was to compare the degree of microbial inactivation and cell damage induced by intense pulsed light (IPL) and short-wavelength ultraviolet (UVC) in <I>Listeria monocytogenes</I> and <I>Escherichia coli</I> O157:H7. The viability of the food-borne pathogens treated with IPL and UVC (254 nm) decreased exponentially with treatment time. Particularly dramatic reductions in <I>L. monocytogenes</I> and <I>E. coli</I> O157:H7 were observed for IPL treatments at energy densities of 376 and 455 W/m<SUP>2</SUP>, with an approximately 7-log reduction for a treatment time of 60–180 s. Also, a 4-log reduction of <I>L. monocytogenes</I> and a 5-log reduction of <I>E. coli</I> O157:H7 were achieved with UVC irradiation for 1200 s. The types and amounts of IPL- and UVC-induced DNA damage in both microorganisms were determined and compared. DNAs from cells irradiated with either IPL or UVC accumulated double-strand breaks (DSBs), single-strand breaks, and cyclobutane pyrimidine dimers, and with a similar pattern; however, more DSBs were detected following UVC than following IPL in both types of microorganism. Transmission electron microscopy observations of IPL- and UVC-induced cell damage clearly indicate that bacterial cell structures were destroyed by IPL treatment but not by UVC treatment.</P> <P><B>Highlights</B></P><P>► Cell damage induced by intense pulsed light (IPL) and UVC irradiation were compared. ► The viability of pathogens decreased exponentially with IPL treatment time. ► More double-strand breaks accumulated in DNA from bacteria treated with IPL than UVC. ► Bacterial cell structures were destroyed by IPL treatment but not by UVC treatment.</P>
Cheigh, C.I.,Chung, E.Y.,Chung, M.S. Applied Science Publishers 2012 Journal of food engineering Vol.110 No.3
Flavanones including hesperidin and narirutin constitute the majority of the flavonoids that occur naturally in citrus fruits. The main purpose of this study was to extract valuable natural flavanones from agricultural by-products such as citrus peels using subcritical water extraction (SWE). Thus, the application of SWE to extraction of flavanones hesperidin and narirutin from Citrus unshiu peel was evaluated, and the effect of key operating conditions was determined by varying the extraction temperature (110-200<SUP>o</SUP>C) and time (5-20min) under high pressure (100+/-10atm). The maximum yields of hesperidin (72+/-5mg/g C. unshiu peel) and narirutin (11.7+/-0.8mg/g C. unshiu peel) were obtained at an extraction temperature of 160<SUP>o</SUP>C for an extraction time of only 10min. These yields accounted for approximately 99% of the total amount of these flavanones in the original material. The SWE was compared with three conventional extraction methods in terms of the extraction time and recovery yields for hesperidin and narirutin. The hesperidin yield by SWE was more than 1.9-, 3.2-, and 34.2-fold higher than those obtained by extraction methods using ethanol, methanol, or hot water, respectively, and the narirutin yield was more than 1.2-, 1.5-, and 3.7-fold higher.
Biosynthesis of L - Ascorbic Acid by Microorganisms in Kimchi Fermentation Process
Hong-Sik Cheigh,Rina Yu,Hyun-Jeong Choi,Hong-Ki Jun 한국식품영양과학회 1996 Preventive Nutrition and Food Science Vol.1 No.1
Kimchi is an important source of various vitamins, minerals, dietary fiber, organic acids and other nutrients. In order to get a basic information for developing vitamins-rich funtional kimchi, we investigated microorganisms which are capable of synthesis of vitamin C in kimchi system. Microorganisms isolated from aliquots of kimchi were screened and cultured by using MRS or nutrient agar medium. L-Ascorbic acid produced by microorganism in medium was measured with high performance liquid chromatography. As the result, we isolated two bacteria strains N7 and N5202 producing L-ascorbic acid from the kimchi system. Morphological and Gram staining experiments showed that N7 was Gram positive bacilli, while N5202 was Gram negative. There were also several bacteria that were considered to synthesize erythorbic acid which is an analog of ascorbic acid. These results suggested that vitamin C-rich functional food could be developed by using the kimchi microorganisms.