Integral Kinetic Model for Studying Quercetin Degradation and Oxidation as Affected by Cholesterol During Heating

The degradation and oxidation of quercetin, as affected by cholesterol during heating at 150 °C, was kinetically studied using non-linear regression models. Both TLC and HPLC were used to monitor the changes of quercetin, cholesterol and cholesterol oxidation products (COPs) during heating. The formation of COPs, including triol, 7-keto, 7α-OH and 7β-OH, was completely inhibited during the initial 30 minute heating period in the presence of 0.02% quercetin, accompanied by reduction in cholesterol peroxidation and degradation. However, the quercetin degradation or oxidation proceeded fast, with the rate constants (h−1) in the presence of nitrogen, oxygen and the combination of oxygen and cholesterol being 0.253, 0.868 and 7.17, respectively. When cholesterol and quercetin were heated together, the rate constants (h−1) of cholesterol peroxidation, epoxidation and degradation were 1.8 × 10−4, 0.016 and 0.19, respectively. The correlation coefficients (r2) for all the oxidative and degradation reactions ranged from 0.82–0.99. The kinetic models developed in this study may be used to predict the degradation and oxidation of quercetin as affected by cholesterol during heating

Formation of Cholesterol Oxides in Irradiated Raw and Cooked Chicken Meat During Storage

The objective of this study was to determine the effect of electron-beam irradiation on the oxidation of cholesterol in raw and cooked chicken meats with different packaging and storage times. Patties were prepared with skinless chicken breasts and legs. Half of the patties were used for raw meat study and the other half for cooked meat work. For cooked samples, patties were cooked in an electric oven to an internal temperature of 70 C. Raw and cooked meat patties were either aerobically or vacuum-packaged before irradiation. Irradiated patties were stored at 4 C up to 2 wk, and the amounts of cholesterol oxides in the patties were analyzed at 0, 7, and 14 d of storage. In raw chicken meat with vacuum packaging, 7β-hydroxycholesterol and β-epoxide were the only two cholesterol oxides present in significant amounts. In raw chicken meat with aerobic packaging, 7α-hydroxycholesterol and 7-keiocholesterol, which were not detected in vacuum-packaged raw chicken meat, were found. 7β-Hydroxycholesterol in raw chicken meat was increased by irradiation and storage time, regardless of packaging. The kinds of cholesterol oxides found in cooked meat were basically the same as those found in raw chicken, but the levels in cooked meats at all storage time were higher than those of the raw meats. With vacuum packaging, irradiation had no consistent effect on the amount of β-epoxide, 7α-hydroxycholesterol, or 7-ketocholesterol, but storage significantly influenced the amount of 7-ketocholesterol, 7β-hydroxycholesterol, and total cholesterol oxides in cooked chicken meat. With aerobic packaging, irradiation significantly increased the formation of 7α-hydroxycholesterol, 7β-hydroxycholesterol, and 7-ketocholesterol in cooked meat stored for 0 and 7 d. After 14 d of storage, however, irradiation had minor effects on the formation of cholesterol oxides in aerobically packaged cooked chicken.This article is published as Lee, J. I., S. Kang, D. U. Ahn, and M. Lee. "Formation of cholesterol oxides in irradiated raw and cooked chicken meat during storage." Poultry science 80, no. 1 (2001): 105-108. doi:10.1093/ps/80.1.105.</p