• Korean Journal of Food Science and Technology
• /
• v.47 no.5
• /
• pp.561-566
• /
• 2015

Effect of the addition of egg yolk lecithin at a concentration of 350 mg/kg on iron-catalyzed autoxidation and chlorophyll-photosensitized oxidation of a water/canola oil emulsion (W/O) during storage at $25^{\circ}C$ was studied based on headspace oxygen consumption and hydroperoxide production. Changes in the phospholipid (PL) composition of the emulsion were determined by high performance liquid chromatography. Headspace oxygen consumption and hydroperoxide content of the emulsion increased with storage time, and addition of egg yolk lecithin did not have any significant effect on these parameters during iron-catalyzed autoxidation and chlorophyll-photosensitized oxidation of the emulsion. PL content of the emulsion decreased during both oxidations, and the degradation rate was higher during autoxidation than during photosensitized oxidation. Phosphatidylcholine content ratio tended to increase during autoxidation. The results suggest that egg yolk lecithin in canola oil emulsion behaves differently during iron-catalyzed autoxidation and chlorophyll-photosensitized oxidation.

• Food Science and Biotechnology
• /
• v.18 no.2
• /
• pp.526-532
• /
• 2009

Quenching mechanisms and kinetics of $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol in photosensitized oxidation of lard were studied. Lard at 0.03, 0.07, 0.11, and 0.3 M in methylene chloride containing $4.4{\times}10^{-6}\;M$ chlorophyll and 0, 0.1, 0.3, and 0.6 mM $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol were stored under light for 4 hr, respectively. Oxidation was determined by headspace oxygen and peroxide value. Tocopherols prevented the photosensitized oxidation of lard (p<0.05). Steady state kinetic study showed that $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol prevented the photosensitized oxidation of lard by quenching singlet oxygen. Singlet oxygen quenching rates of $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol by headspace oxygen depletion were 1.86, 2.39, 2.47, and $2.11{\times}10^7/M/sec$, respectively. The quenching rates of $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol by peroxide value were 1.42, 1.11, 0.97, and $0.42{\times}10^7/M/sec$, respectively. The quenching rates of tocopherols were slightly different depending on the measurements of oxidation.

• Journal of Photoscience
• /
• v.10 no.1
• /
• pp.175-180
• /
• 2003

Zeolite, Nafion membranes and vesicles were used as microreactors to control the pathway of photosensitized oxidation of alkenes and remarkable selectivity was achieved.

• Korean Journal of Food Science and Technology
• /
• v.46 no.2
• /
• pp.127-134
• /
• 2014

This study was performed to evaluate the effects of sesame oil addition to a tuna oil-enriched emulsion during chlorophyll-photosensitized oxidation. The emulsion principally consisted of tocopherol-stripped canola and tuna oil with or without sesame oil, acetic acid, phospholipids, and xanthan gum. Chlorophyll b was added to promote the production of singlet oxygen upon exposure to light. The oxidation of oil in the emulsion was evaluated by determining the peroxide value (POV) and conjugated dienoic acid (CDA) contents. Concentrations of minor compounds in the emulsion were monitored. Increasing POV and CDA contents in the emulsion were paralleled with decreased docosahexaenoic acid during oxidation, and oxidation was inhibited by the addition of sesame oil. Chlorophyll, polyphenols, tocopherol, and phospholipids were degraded during oxidation of the emulsion; however, their degradation was slowed down by the addition of sesame oil. Lignans in the emulsions containing added sesame oil were barely changed, suggesting that they quenched singlet oxygen physically. Polyphenols were the most effective in improving the stability of tuna oil-enriched emulsions during chlorophyll-photosensitized oxidation.

• Bulletin of the Korean Chemical Society
• /
• v.7 no.1
• /
• pp.78-81
• /
• 1986

The photosensitized lysis of egg lecithin lipid membranes (liposomes) have been performed to UV-B light (270-320 nm) by L-tryptophan(L-Trp) and its peptide such as N-acetylphenylalanyl-L-tryptophan(NAPT) incorporated in the liposomes(ca. 0.1% by weight) or in the external buffer (0.1-0.3 mM). Requirement of oxygenation suggests that the lysis of liposomes is caused by the photosensitized oxidation of lipids. There was significant protection against lysis photosensitized by Trp in the external buffer by low concentration of ferricyanide (0.8 mM), but there was no effect on the lytic efficiency by $N_3^-$ which is singlet oxygen($^1O_2$) quencher, indicative of an electron transfer mechanism involved in the photosensitization. The small change of the lytic efficiency with increasing pH from 4 to 9 was interpreted by large target theory and subsequently indicates that superoxide($O_2^-$) may be an active intermediate for the oxidation. The efficiency of photosensitization of Trp was higher than that of NAPT under the same experimental condition. The weak lytic efficiency of liposomes photosensitized by NAPT was enhanced by incorporating NAPT in liposomes, but it was again quenched by ${\beta}$-carotene incorporated in the bilayer of liposomes. These results indicate that a portion of liposome lysis may be due to $^1O_2$ formation from the excited NAPT.

• Proceedings of the Korean Society of Potoscience Conference
• /
• 2005.06a
• /
• pp.18-18
• /
• 2005

• Rapid Communication in Photoscience
• /
• v.4 no.2
• /
• pp.41-44
• /
• 2015

Biomolecular photo-damaging activity of a water-soluble cationic porphyrin was examined using human serum albumin (HSA), a water-soluble protein as a target biomolecule model by a fluorometry. Dichlorophosphorus(V) tetraphenylporphyrin ($Cl_2P(V)TPP$), was synthesized and used as a photosensitizer. This porphyrin could bind to HSA and cause the photosensitized oxidation of HSA through the singlet oxygen generation and the oxidative photo-induced electron transfer (ET). Near infrared emission spectroscopy demonstrated the photosensitized singlet oxygen generation by this porphyrin. Decrement of the fluorescence lifetime of $Cl_2P(V)TPP$ by HSA supported the ET mechanism. Furthermore, the estimated Gibb's energy indicated that the ET mechanism is possible in the terms of energy. Because oxygen concentration in cancer cell is relatively low, ET mechanism is considered to be advantageous for photosensitizer of photodynamic therapy.

• Journal of Photoscience
• /
• v.6 no.3
• /
• pp.85-90
• /
• 1999

Supramolecular photochemistry is concerned with systems where non-covalent interactions become significant or dominate in determining the chemistry of guest/host systems. The photocycloaddition of diaryl compounds and the photosensitized oxidation of alkenes included in zeolites, low-density polyethylene films and Nafion membranes is the subject of this report.

• The Korean Journal of Food And Nutrition
• /
• v.37 no.1
• /
• pp.48-56
• /
• 2024

Effects of glutamic acid (Glu) and monosodium glutamate (MSG) on oxidative stability of oil-in-water (O/W) emulsions with different emulsifier charges during riboflavin (RF) photosensitization were evaluated by analyzing headspace oxygen content and conjugated dienes. Cetyltrimethylammonium bromide (CTAB), Tween 20, and sodium dodecyl sulfate (SDS) were used as cationic, neutral, and anionic emulsifiers, respectively. Glu acted as an antioxidant in CTAB- and Tween-20-stabilized O/W emulsions during RF sensitization, whereas Glu acted as prooxidants in SDS-stabilized O/W emulsions in the dark. However, adding MSG did not have a constant impact on the degree of oxidation in O/W emulsions irrespective of the emulsifier charge. In RF-photosensitized O/W emulsions, the emulsifier charge had a greater influence on antioxidant properties of Glu than on those of MSG.

• Korean Journal of Food Science and Technology
• /
• v.37 no.5
• /
• pp.717-722
• /
• 2005

Formation mechanisms of light-induced volatile compounds were studied using riboflavin-photosensitized oleic acid model systems. Volatile compounds in model systems with 4000 ppm riboflavin at $35^{\circ}C$ under light or in the dark for 39 hr were isolated and identified by a combination of solid phase microextraction (SPME), gas chromatography (GC), and mass spectrometry (MS). Total volatiles in oleic acid with riboflavin under light for 13, 26, and 39 hr increased by 90, 190, and 270%, respectively, compared to those in oleic acid without riboflavin under light. Total volatiles in samples without riboflavin under light or samples with riboflavin in the dark were not significant in tested conditions (p>10.05). Riboflavin did not act as a photosensitizer when it was dispersed in oleic acid. Heptane, octane, heptanal, octanal, nonanal, and 2-nonenal were significantly increased in riboflavin-photosensitized samples compared to those in samples without riboflavin (p<0,05). Light-induced volatile compounds including heptanal and 2-nonenal from oleic acid could be explained using singlet oxygen oxidation, the formation mechanism of which were not understood using triplet oxygen oxidation. These results will help to understand volatile formation in oleic acid containing foods stored under light.