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Ha J.-W.,Center for Food and Bioconvergence | Back K.-H.,Center for Food and Bioconvergence | Kim Y.-H.,Center for Food and Bioconvergence | Kang D.-H.,Center for Food and Bioconvergence | Kang D.-H.,Seoul National University of Science and Technology
Food Microbiology | Year: 2016

In this study, the efficacy of using UV-C light to inactivate sliced cheese inoculated with Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes and, packaged with 0.07 mm films of polyethylene terephthalate (PET), polyvinylchloride (PVC), polypropylene (PP), and polyethylene (PE) was investigated. The results show that compared with PET and PVC, PP and PE films showed significantly reduced levels of the three pathogens compared to inoculated but non-treated controls. Therefore, PP and PE films of different thicknesses (0.07 mm, 0.10 mm, and 0.13 mm) were then evaluated for pathogen reduction of inoculated sliced cheese samples. Compared with 0.10 and 0.13 mm, 0.07 mm thick PP and PE films did not show statistically significant reductions compared to non-packaged treated samples. Moreover, there were no statistically significant differences between the efficacy of PP and PE films. These results suggest that adjusted PP or PE film packaging in conjunction with UV-C radiation can be applied to control foodborne pathogens in the dairy industry. © 2016. Source

Kang J.-W.,Center for Food and Bioconvergence | Kang J.-W.,Seoul National University of Science and Technology | Kang D.-H.,Center for Food and Bioconvergence | Kang D.-H.,Seoul National University of Science and Technology
International Journal of Food Microbiology | Year: 2016

This study was undertaken to evaluate the effect of vacuum impregnation applied to the washing process for removal of Salmonella Typhimurium and Listeria monocytogenes from broccoli surfaces. Broccoli was inoculated with the two foodborne pathogens and treated with simple dipping washing or with vacuum impregnation in 2% malic acid for 5, 10, 20, or 30min. There were two methods of vacuum impregnation: continuous and intermittent. After 30min of 101.3kPa (=14.7psi, simple dipping), 61.3kPa (=8.9psi), and 21.3kPa (=3.1psi) of continuous vacuum impregnation treatment, there were 1.6, 2.0, and 2.4log10CFU/g reductions of S. Typhimurium and 1.5, 1.7, and 2.3log10CFU/g reductions of L. monocytogenes, respectively. After 30min of 101.3, 61.3, and 21.3kPa of intermittent vacuum impregnation treatment, there were 1.5, 2.3, and 3.7log10CFU/g reductions of S. Typhimurium and 1.6, 2.1, and 3.2log10CFU/g reductions of L. monocytogenes, respectively. Scanning electron photomicrographs showed that bacteria tend to attach to or become entrapped in protective sites after simple wash processing (dipping). However, most bacteria were washed out of protective sites after intermittent treatment. Direct treatment of cell suspensions with vacuum impregnation showed that it had no inactivation capacity in itself since there were no significant differences (P≥0.05) between the reduction rates of non- and vacuum impregnation treatment. These results demonstrate that the increased antimicrobial effect of vacuum impregnation can be attributed to increased accessibility of sanitizer and an enhanced washing effect in protected sites on produce. Color, texture and titratable acidity values of broccoli treated with intermittent vacuum impregnation in 2% malic acid for 30min were not significantly (P≥0.05) different from those of untreated samples even though a storage interval was needed for titratable acidity values to be reduced to levels comparable to those of untreated controls. © 2015. Source

Ban G.-H.,Center for Food and Bioconvergence | Kang D.-H.,Center for Food and Bioconvergence
International Journal of Food Microbiology | Year: 2016

This study was undertaken to evaluate the effectiveness of superheated steam (SHS) on the inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, Salmonella Enteritidis phage type (PT) 30 and Listeria monocytogenes on almonds and in-shell pistachios and to determine the effect of superheated steam heating on quality by measuring color and texture changes. Almonds and in-shell pistachios inoculated with four foodborne pathogens were treated with saturated steam (SS) at 100. °C and SHS at 125, 150, 175, and 200. °C for various times. Exposure of almonds and pistachios to SHS for 15 or 30 s at 200. °C achieved >. 5 log reductions among all tested pathogens without causing significant changes in color values or texture parameters (P> 0.05). For both almonds and pistachios, acid and peroxide values (PV) following SS and SHS treatment for up to 15 s and 30 s, respectively, were within the acceptable range (PV < 1.0. meq/kg). These results show that thermal application of 200. °C SHS treatment for 15 s and 30 s did not affect the quality of almonds and pistachios, respectively. Therefore, SHS treatment is a very promising alternative technology for the tree nuts industry by improving inactivation of foodborne pathogens on almonds and pistachios while simultaneously reducing processing time. © 2016 Elsevier B.V. Source

Bae Y.-H.,Center for Food and Bioconvergence | Bae Y.-H.,Seoul National University | Kweon D.-H.,Sungkyunkwan University | Park Y.-C.,Kookmin University | And 2 more authors.
Process Biochemistry | Year: 2014

Galactose is one of the major sugar components of red seaweeds along with glucose. In Saccharomyces cerevisiae, synthesis of galactose-metabolizing enzymes (the Leloir proteins) is under tight and complex regulation in the presence of glucose by a mechanism called catabolite repression. As a result, when both sugars are concurrently present in the medium under oxygen-limited conditions, the yeast cannot utilize galactose even after glucose consumption. Research efforts on mixed sugar fermentation of glucose/galactose, therefore, were made in the presence of oxygen, thereby resulting in sequential substrate consumption, and low ethanol yield and productivity. In this study, mixed sugar fermentation of glucose and galactose in oxygen-limited conditions was achieved by deleting the HXK2 gene, a moonlighting protein acting as hexokinase or repressor involved in catabolite repression of S. cerevisiae. Remarkably, the S. cerevisiae D452-2δhxk2 strain utilized galactose after glucose depletion without a diauxic lag period, whereas the parental strain could not use galactose at all under oxygen-limited conditions. The δhxk2 strain fermented galactose at the consumption rate of 3.02 ± 0.10 g/L/h to produce ethanol with a yield of 0.44 ± 0.01 g ethanol/g galactose. Complementation of the δhxk2 strain with the plasmid-harbored HXK2 gene under the control of various promoters clearly showed that the galactose consumption rates were inversely related to the mRNA levels of the HXK2 gene. The transcription of the GAL genes was dramatically elevated by deleting the HXK2 gene, whereas the expressions of hexokinase genes were not significantly affected. We concluded that the HXK2-deleted strain is able to efficiently utilize both glucose and galactose in the oxygen-limited conditions by alleviating catabolite-repression. © 2014 Elsevier Ltd. Source

Islam M.A.,Seoul National University | Islam M.A.,Research Institute for Agriculture and Life science | Islam M.A.,Center for Food and Bioconvergence | Firdous J.,Seoul National University | And 8 more authors.
International Journal of Nanomedicine | Year: 2012

Chitosan, a natural biodegradable polymer, is of great interest in biomedical research due to its excellent properties including bioavailability, nontoxicity, high charge density, and mucoadhesivity, which creates immense potential for various pharmaceutical applications. It has gelling properties when it interacts with counterions such as sulfates or polyphosphates and when it crosslinks with glutaraldehyde. This characteristic facilitates its usefulness in the coating or entrapment of biochemicals, drugs, antigenic molecules as a vaccine candidate, and microorganisms. Therefore, chitosan together with the advance of nanotechnology can be effectively applied as a carrier system for vaccine delivery. In fact, chitosan microspheres have been studied as a promising carrier system for mucosal vaccination, especially via the oral and nasal route to induce enhanced immune responses. Moreover, the thiolated form of chitosan is of considerable interest due to its improved mucoadhesivity, permeability, stability, and controlled/extended release profile. This review describes the various methods used to design and synthesize chitosan microspheres and recent updates on their potential applications for oral and nasal delivery of vaccines. The potential use of thiolated chitosan microspheres as next-generation mucosal vaccine carriers is also discussed. © 2012 Islam et al, publisher and licensee Dove Medical Press Ltd. Source

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