Jihyeon Lee

Antioxidant activities of distiller dried grains with solubles as protein films containing tea extracts and their application in the packaging of pork meat.

Distiller dried grains with solubles (DDGS) as protein (DP) films were prepared. Additionally, to prepare anti-oxidant films, green tea extract (GTE), oolong tea extract (OTE), and black tea extract (BTE) were incorporated into the DP films. Consequently, the incorporation of the tea extracts did not alter the physical properties of the films much, whereas the antioxidant activities, such as ABTS and DPPH radical scavenging activities were observed. To apply the DP films containing tea extracts to food packaging, pork meat was wrapped with the films and stored at 4 °C for 10 d. During storage, the pork meat wrapped with the DP films containing GTE, OTE, and BTE had less lipid oxidation than did the control. Among the tea extracts, the DP film containing GTE had the greatest antioxidant activity. These results indicate that the DP films containing green tea extracts can be utilized as an anti-oxidative packaging material for pork meat.

Analysis of explosives using corona discharge ionization combined with ion mobility spectrometry-mass spectrometry.

Corona discharge ionization combined with ion mobility spectrometry-mass spectrometry (IMS-MS) was utilized to investigate five common explosives: cyclonite (RDX), trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), cyclotetramethylenetetranitramine (HMX), and 2,4-dinitrotoluene (DNT). The MS scan and the selected ion IMS analyses confirmed the identities of the existing ion species and their drift times. The ions observed were RDX·NO3(-), TNT(-), PETN·NO3(-), HMX·NO3(-), and DNT(-), with average drift times of 6.93 ms, 10.20 ms, 9.15 ms, 12.24 ms, 11.30 ms, and 8.89 ms, respectively. The reduced ion mobility values, determined from a standard curve calculated by linear regression of (normalized drift times)(-1) versus literature K0 values, were 2.09, 1.38, 1.55, 1.15, 1.25, and 1.60 cm(2) V(-1) s(-1), respectively. The detection limits were found to be 0.1 ng for RDX, 10 ng for TNT, 0.5 ng for PETN, 5.0 ng for HMX, and 10 ng for DNT. Simplified chromatograms were observed when nitrogen, as opposed to air, was used as the drift gas, but the detection limits were approximately 10 times worse (i.e., less sensitivity of detection).

Characterization of a starfish gelatin film containing vanillin and its application in the packaging of crab stick

To explore the use of starfish gelatin (SFG) films as a biodegradable material, SFG from starfish was extracted and used as a film material. In addition, to provide antimicrobial activity and enhanced flavor of SFG films, vanillin was incorporated. As the concentration of vanillin increased, the tensile strength of the films increased and water vapor permeability decreased. With regard to the structural characteristics of SFG films containing vanillin, the microstructure of the SFG films was not affected by the addition of vanillin. In addition, the SFG films containing vanillin exhibited antimicrobial activity against Listeria monocytogenes. As the application of the SFG films, crab sticks were packed with SFG films containing 0.05% vanillin. During storage, the populations of L. monocytogenes inoculated on crab sticks wrapped with SFG films containing vanillin were lower than those on the control sample, suggesting that SFG films containing vanillin can be useful in active food packaging.

Enhanced Detection of Glycans by MALDI-TOF Mass Spectrometry Using a Binary Matrix of 2,5-Dihydroxybenzoic Acid and 2,6-Dihydroxybenzoic Acid

Glycans released from ovalbumin by PNGase F were analyzed by matrix-assisted laser desorption/ionization time-of- flight (MALDI-TOF) mass spectrometry using three different dihydroxybenzoic acid (DHB) matrix systems: 2,5-DHB, 2,6- DHB, and a 2,5-DHB/2,6-DHB binary matrix. Relative to the results obtained with the single-component matrices (2,5-DHB or 2,6-DHB), the 2,5-DHB/2,6-DHB binary matrix boasted lower background noise and higher sensitivity. A total of 16 glycan peaks were observed using the 2,5-DHB/2,6-DHB binary matrix, while only 10 and 9 glycan peaks were observed using the 2,5- DHB and 2,6-DHB matrices, respectively. The current study investigated the effectiveness of a new binary matrix composed of 2,5-DHB and 2,6-DHB in analyses of glycans released from ovalbumin by enzymatic cleavage with PNGase F. The mass spectrum acquired with the binary matrix was compared with those obtained using the single matrix materials (2,5-DHB or 2,6-DHB). Experimental All chemicals were obtained from Sigma-Aldrich (St. Louis, MO, USA) unless otherwise specified. To perform deglyc- osylation, 2 mg of ovalbumin (catalog number: A5503) was mixed with 1 unit of PNGase F (catalog number: P7367) in 200 µL of 50 mM ammonium bicarbonate buffer solution for 2 h at 37 o C with gentle mixing. To prepare the 2,5-DHB/2,6-DHB

Microwave-assisted Weak Acid Hydrolysis of Proteins

Myoglobin was hydrolyzed by microwave-assisted weak acid hydrolysis with 2% formic acid at 37 o C, 50 o C, and 100 o C for 1 h. The most effective hydrolysis was observed at 100 o C. Hydrolysis products were investigated using matrix- assisted laser desorption/ionization time-of-flight mass spectrometry. Most cleavages predominantly occurred at the C-termini of aspartyl residues. For comparison, weak acid hydrolysis was also performed in boiling water for 20, 40, 60, and 120 min. A 60- min weak acid hydrolysis in boiling water yielded similar results as a 60-min microwave-assisted weak acid hydrolysis at 100 o C. These results strongly suggest that microwave irradiation has no notable enhancement effect on acid hydrolysis of pro- teins and that temperature is the major factor that determines the effectiveness of weak acid hydrolysis.

Optimization in Detecting Multiply-charged Protein Ions using MALDI TOF-MS

The effects of trifluoroacetic acid (TFA) were evaluated on the generation of multiply charged ions of cytochrome c in a 2-nitrophloroglucinol (2-NPG) matrix in high-vacuum, matrix-assisted laser desorption/ionization time-of-flight mass spec- trometry (MALDI-TOF MS). The presence of 1% TFA in the 2-NPG matrix solution was more effective in generating multiply charged protein ions than matrix solutions containing 0.1% or 0% TFA. Regarding the matrix itself, with 1% TFA, 2-NPG was significantly more effective in generating multiply charged ions than 2,5-dihydroxybenzoic acid (2,5-DHB). The maximum charge state of cytochrome c was +8 when using a 2-NPG matrix containing 1% TFA.