Oxidative Stability Of Cholesterol Research Articles

Estabilidade oxidativa do colesterol em ovo integral em pó

Ovos são importantes como alimento e como matéria-prima industrial. Ao mesmo tempo, têm elevada concentração de colesterol, principalmente quando desidratado. O colesterol, por sua vez, está sujeito à oxidação durante o processamento e/ou estocagem, formando, em conseqüência, derivados oxidados com atividades tóxicas, entre as quais a aterogenicidade. Foi avaliada, neste trabalho, a estabilidade do colesterol em ovo integral em pó comercial, através da ocorrência do 7-cetocolesterol livre, quantificado por cromatografia líqüida de alta eficiência, depois da extração dos lípides totais e separação em coluna de Florisil. O 7-cetocolesterol livre ocorreu em todos os três lotes das cinco marcas analisadas de ovo integral em pó, em teor médio de 84,01±5,34 mig/g de lípides. Não foi possível indicar clara evolução da oxidação do colesterol durante a estocagem do produto por até 224 dias, à temperatura ambiente; no entanto, uma correlação significativa (r = 0,8093) pôde ser observada entre o 7-cetocolesterol livre e as substâncias reativas ao ácido tiobarbitúrico (TBARS).

Oxidation of cholesterol in mayonnaise during storage

The oxidative stability of cholesterol in commercial mayonnaise under different storage conditions was evaluated by measuring cholesterol oxides (COs), 7-ketocholesterol (7-Keto), 25-hydroxycholesterol (25-OH), 7α-hydroxycholesterol (7α-OH) and 7β-hydroxycholesterol (7β-OH) using HPLC. Oxidation of cholesterol was indicated within about 15 days after manufacture by the presence of 7-Keto. Oxidation increased during storage at 4 and 25 °C (being greater at 25 °C) for 165 days in darkness, as indicated by the presence of 7-Keto, 25-OH, 7α-OH and 7β-OH. There was a strong correlation between COs and PV (peroxide value) [ r 2=0.95 (4 °C) and r 2=0.96 (25 °C)] during the process of oxidation. The pattern of fatty acids was not affected during the period of the experiment. Temperature and time were important factors in the oxidative stability of cholesterol. Total formation of COs during 165 days was 20.3 μg/g at 4 °C and 30.2 μg/g at 25 °C.

Stability of Cholesterol and Paprika Carotenoids in Egg Powders as Influenced by Dietary and Processing Treatments

The effects of dietary α-tocopherol and/or oleoresin paprika (OP) on cholesterol and carotenoid stability in egg powders during spray drying and subsequent storage were investigated. Cholesterol oxidation and loss of carotenoids in eggs dried with a direct gas-fired spray dryer were greater (P < 0.05) than in eggs dried using an indirect (electric) heating system. Dietary supplementation of α-tocopherol acetate (200 mg kg -1 feed) significantly increased (P < 0.01) the oxidative stability of cholesterol and carotenoids in eggs dried with the direct heating system. Supplementation of OP (7.5 μg g -1 egg lipids) through diet or by direct addition to liquid eggs did not affect the formation of cholesterol oxidation products (COPS) during storage. However, increased concentrations of OP in liquid eggs (15 and 30 μg g -1 lipids) suppressed the formation of COPS during processing and subsequent storage.

Stability of Cholesterol and Paprika Carotenoids in Egg Powders as Influenced by Dietary and Processing Treatments

The effects of dietary α-tocopherol and/or oleoresin paprika (OP) on cholesterol and carotenoid stability in egg powders during spray drying and subsequent storage were investigated. Cholesterol oxidation and loss of carotenoids in eggs dried with a direct gas-fired spray dryer were greater (P<0·05) than in eggs dried using an indirect (electric) heating system. Dietary supplementation of α-tocopherol acetate (200 mg kg−1 feed) significantly increased (P<0·01) the oxidative stability of cholesterol and carotenoids in eggs dried with the direct heating system. Supplementation of OP (7·5 μg g−1 egg lipids) through diet or by direct addition to liquid eggs did not affect the formation of cholesterol oxidation products (COPS) during storage. However, increased concentrations of OP in liquid eggs (15 and 30 μg g−1 lipids) suppressed the formation of COPS during processing and subsequent storage.

Cholesterol Oxidation in Egg Yolk Powder During Storage and Heating as Affected by Dietary Oils and Tocopherol

ABSTRACTThe effects of feeding flax, sunflower, palm and fish oils, with and without tocopherols, to laying hens was investigated on oxidative stability of cholesterol in egg yolk powders. Storage of spray‐dried egg yolk powders at room temperature resulted in loss (p &lt;0.05) of tocopherols. The initial levels of spray‐dried yolk cholesterol oxides were 7–10 ppm and increased (p &lt;0.05) with storage. The cholesterol oxide contents in the egg yolk powders were: fish &gt; flax &gt; sunflower &gt; palm. Heating egg yolk powder increased (p &lt;0.05) the amounts of total cholesterol oxides. Diets with tocopherol supplementation resulted in a decrease (p &lt;0.05) of cholesterol oxides during storage and heating.

Cholesterol oxidation in muscle tissue

Three model systems were designed to monitor the oxidative stability of cholesterol in different lipid environments. The cholesterol moiety of cholesteryl linoleate oxidized to a greater extent than that of cholesteryl stearate and free cholesterol. Cholesterol oxidized when dispersed with either phosphatidyl choline or adipose tissue, further demonstrating that cholesterol oxidation is affected by the surrounding lipid environment. Oxidation of cholesterol in muscle tissue was also affected by the membrane environment. Vitamin E supplementation of veal calves improved the oxidative stability of muscle lipids and cholesterol. Comparison was made of the oxidative stability of retail beef lipids, including cholesterol, with the oxidative stability of veal lipids and cholesterol. The results supported the hypothesis that if initiation of lipid oxidation occurs in the muscle membranes, the fat content of the meat should not influence the stability of the lipids to initial oxidation.

Effects of Packaging and Light Source on the Oxidative Stability of Cholesterol in Sutter

ABSTRACTThe effect of package material light transmission on the oxidative stability of cholesterol in butter exposed to fluorescent light was investigated. Only aluminum foil prevented cholesterol oxidation after 15 days of exposure. Margarine wrap, opaque parchment, wet strength dry wax paper, and polyethylene film were not effective. These results indicate that cholesterol oxidation occurred via singlet oxygen attack as well as free radical mechanisms. Daylight elicited oxidation in butter at 22°C at a greater rate than did fluorescent roomlight. Cholesterol oxidation products were detectable in some samples after 2 wk, but concentrations were very low and restricted positive identification by the analytical procedure employed in the study.

Photooxidation of Cholesterol in Butter

ABSTRACTThe effect of exposure to fluorescent light on the oxidative stability of cholesterol in unpackaged butter was investigated. Oxidation of cholesterol in butter occurred, although the oxidation products were detectable only after prolonged exposure to light. Cholesterol oxides were more concentrated at the surface than throughout the entire butter block and were detectable after 8 days of exposure to light. 5‐Cholesten‐313, 7α‐diol and its 7β‐epimer, products of free radical attack on cholesterol, were detected among the oxidation products, along with a compound suspected to be 6‐cholesten‐3β, 5α‐diol. This latter compound is only known to form following singlet oxygen attack on cholesterol.