Keum-Il Jang

Stability of chitosan nanoparticles for L-ascorbic acid during heat treatment in aqueous solution.

This study investigated the stability and characteristics of L-ascorbic acid (AA)-loaded chitosan (CS) nanoparticles during heat processing in aqueous solutions. AA-loaded CS nanoparticles were prepared by ionic gelation of CS with tripolyphosphate (TPP) anions. The smallest CS nanoparticles (170 nm) were obtained with a CS concentration of 1.5 mg/mL and a TPP concentration of 0.6 mg/mL. As the concentration of AA increased from 0.1 to 0.3 mg/mL, the particle size increased, while the zeta potential decreased, and the encapsulation efficiency of AA remained within a fixed range (10-12%). During heat processing at various temperatures, the size and zeta potential of the particles decreased rapidly in the first 5 min and then slowly fell to the regular range. At the beginning of the release profiles, the burst release-related stability of the surface increased with the temperature. Then, the release of the internal AA was constantly higher with a longer release time. Consequently, it was confirmed that the stability of AA-loaded CS nanoparticles was affected by temperature but that the internal stability was greater than the surface stability. These results demonstrate the stability of CS nanoparticles for AA during heat processing and suggest the possible use of AA-loaded CS nanoparticles to enhance antioxidant effects because of the continuous release of AA from CS nanoparticles in food processing.

Antibacterial Effects of Leek and Garlic Juice and Powder in a Mixed Strains System

The aim of this study was to evaluate the antimicrobial activities of leek and garlic extract juice and powder against Escherichia coli, Salmonella enteritidis, and Staphylococcus aureus in a single strain and a mixed strains system. Garlic juice and powder showed higher antimicrobial activity against Sta. aureus than that of E. coli or S. enteritidis. The antimicrobial activities of the leek and garlic powders decreased with increasing temperature and time, but stabilized at various pHs. The antimicrobial effects of mixtures of various ratios between the leek and garlic extracts increased with an increase in garlic extract content. No synergistic effects by the leek and garlic mixtures were observed. In a mixed strains system, the antimicrobial effects of leek and garlic powder were similar to those in a single strain system.The aim of this study was to evaluate the antimicrobial activities of leek and garlic extract juice and powder against Escherichia coli, Salmonella enteritidis, and Staphylococcus aureus in a single strain and a mixed strains system. Garlic juice and powder showed higher antimicrobial activity against Sta. aureus than that of E. coli or S. enteritidis. The antimicrobial activities of the leek and garlic powders decreased with increasing temperature and time, but stabilized at various pHs. The antimicrobial effects of mixtures of various ratios between the leek and garlic extracts increased with an increase in garlic extract content. No synergistic effects by the leek and garlic mixtures were observed. In a mixed strains system, the antimicrobial effects of leek and garlic powder were similar to those in a single strain system.

Physicochemical properties and cell permeation efficiency of l-ascorbic acid loaded nanoparticles prepared with N-trimethyl chitosan and N-triethyl chitosan

The physicochemical properties and permeation efficiency of l-ascorbic acid (AA)-loaded nanoparticles (NPs) prepared using N-trimethyl chitosan (TMC) and Ntriethyl chitosan (TEC) were investigated. The sizes of AA-TMC-NPs and AA-TEC-NPs were 568±50 and 150±15 nm, respectively and both zeta potential values were slightly positively charged. The encapsulation efficiency (EE) of AA-TMC-NPs was consistently between 40 and 45%, but the EE of AA-TEC-NPs varied between 18 and 56%. The release rate increased with increased temperatures for both NPs. AA-TMC-NPs exhibited an initial burst release, while AA-TEC-NPs exhibited a controlled release, increasing rapidly after 2 h. The pH-related release pattern was similar to the temperature-related release pattern. The permeation efficiency into Caco-2 cells, in order from lowest to highest, was AA, an AA mixture with TMC, an AA mixture with TEC, AA-TMC-NPs, and AA-TEC-NPs. Both NPs showed potential to enhance the permeability of AA.

Antioxidant activities and physicochemical properties of tteokbokki rice cakes containing cinnamon powder

Antioxidant activities and physicochemical properties of tteokbokki rice cakes containing different amounts of cinnamon powder were evaluated. The pH and the L values (chromaticity) decreased, and the moisture content and the a (red) value increased with an increasing cinnamon concentration. The b (yellow) value increased at 1% (w/w) cinnamon powder. The hardness and chewiness increased with an increase in the cinnamon powder content, while the adhesiveness and cohesiveness decreased. The antioxidant effects, total polyphenol content, and DPPH and ABTS radical scavenging activities all increased with an increased cinnamon concentration. Cinnamon can promote expansion of tteokbokki markets, and rice consumption.

Effect of temperature and ph on interconversion between fructose and mannose catalyzed by Thermotoga neapolitana mannose-6-phosphate isomerase

The gene encoding a putative mannose-6-phosphate isomerase (TnMPI) from Thermotoga neapolitana DSM4359 was cloned and expressed in Escherichia coli. TnMPI showed the highest isomerization activity between d-fructose and d-mannose at 75°oC in 50 mM Tris-HCl buffer (pH 7.5) containing 1 mM of Cu2+. TnMPI can be activated by some divalent metal ions, such as Cu2+, Mn2+, and Co2+. In the presence of 1 mM Cu2+, TnMPI activity on conversion from d-fructose to d-mannose was significantly enhanced up to 271% of that without Cu2+. In addition, its isomerization equilibrium between d-fructose and Dmannose was strongly affected by reaction temperature and pH. As reaction temperature decreased from 95 to 55°C, the equilibrium ratio of d-fructose to d-mannose was gradually shifted from 73:27 to 55:45. As reaction pH decreased from pH 8.5 to 5.5, the equilibrium ratio of Dfructose to d-mannose was shifted from 68:32 to 49:51.

Effects of a Pre-Filter and Electrolysis Systems on the Reuse of Brine in the Chinese Cabbage Salting Process

In this study, the effects of a pre-filter system and electrolysis system on the safe and efficient reuse of brine in the cabbage salting process were investigated. First, sediment filter-electrolyzed brine (SF-EB) was selected as brine for reuse. Then, we evaluated the quality and microbiological properties of SF-EB and Chinese cabbage salted with SF-EB. The salinity (9.4%) and pH (4.63) of SF-EB were similar to those of control brine (CB). SF-EB turbidity was decreased (from 0.112 to 0.062) and SF-EB residual chlorine (15.86 ppm) was higher than CB residual chlorine (0.31 ppm), and bacteria were not detected. Salinity (2.0%), pH (6.21), residual chlorine (0.39 ppm), chromaticity, hardness, and chewiness of cabbage salted with SF-EB were similar to those of cabbage salted with CB. The total bacterial count in cabbage salted with CB was increased as the number of reuses increased (from 6.55 to 8.30 log CFU/g), whereas bacteria in cabbage salted with SF-EB was decreased (from 6.55 to 5.21 log CFU/g). These results show that SF-EB improved the reusability of brine by removing contaminated materials and by sterilization.

Identification and expression profiling of flax (Linum usitatissimum L.) polyamine oxidase genes in response to stimuli

Abstract Polyamine oxidases (PAOs) are known to be involved in either the terminal catabolism or the back conversion of polyamines, which affect a range of physiological processes, including growth, development, and stress responses. In this study, based on genome-wide analysis, we identified five putative PAO genes (LuPAO1 to LuPAO5) in flax (Linum usitatissimum L.) that contain the amino-oxidase domain and FAD-binding-domain. The expression analysis using quantitative real-time PCR revealed spatial variations in the expression of LuPAOs in different organs. In addition, the expression level of LuPAOs in the flax cell suspension culture was increased by treatment with methyl-jasmonate (MeJA) or pectin, but not with salicylic acid or chitosan. This indicates that LuPAOs might be involved in the MeJA-mediated biological activities. Taken together, our genome-wide analysis of PAO genes and expression profiling of these genes provide the first step toward the functional dissection of LuPAOs.

Quality Characteristics and Antioxidant Activity of Espresso Coffee Prepared with Green Bean Fermented by Lactic Acid Bacteria

This study investigated the quality characteristics and antioxidant activities of espresso coffee prepared with green bean fermented by lactic acid bacteria. First, 10, 20, and 30% (w/v) green beans were fermented by Lactobacillus acidophilus KCTC 3145 at 37°C for 0, 12, and 24 h, respectively. Cells of L. acidophilus gradually increased with increasing green bean content and fermentation time. After drying fermented green beans, coffee powders were prepared by roasting (city level) and grinding (<75 mesh). Then, espresso coffee was extracted using coffee powder. The pH and chromaticity (L*, a*, and b* values) of espresso coffee decreased with fermentation time, whereas total acidity, total soluble solid contents, and brown color intensity increased. The pH level decreased with increasing contents of fermented green bean and total acidity increased. However, chromaticity, total soluble solid contents, and brown color intensity remained within a limited range. The antioxidant activities, including total polyphenol content, and DPPH and ABTS radical scavenging activities increased with increasing green bean content and fermentation time. Finally, sensory evaluation -for taste, color, flavor, and overall preferencerevealed espresso coffee prepared with fermentation of 30% (w/v) green bean received the highest scores. Green bean fermented by lactic acid bacteria enhanced quality characteristics and antioxidant activities of espresso coffee, showing that lactic acid bacteria fermentation has potential use in the espresso coffee industry.