Oxidation of Cholesterol in Foods and Its Importance for Human Health

Cholesterol oxidation products are present in different biological pathways and in oxidized cholesterol-containing food. More than 70 molecules have been identified and most of them present cytotoxic, atherogenic, mutagenic, and carcinogenic effects. They can change important characteristics of the cellular membrane and inhibit the biosynthesis of several molecules. Foods of animal origin can develop these derivatives by the action of oxygen, heat, polyunsaturated fatty acids, water, pH, radiation, and inadequate packaging and storage, affecting their quality and exposing consumers to potential health problems. Despite the interest in cholesterol oxidation products, safe biological levels for them have not yet been established. The purpose of this review is to examine cholesterol oxidation products in foods and examine their importance for human health.     

Cholesterol Oxides in Foods of Animal Origin

The earliest discovery of an oxidation product of cholesterol from a natural source was reported in 1940. Additional discoveries of cholesterol oxidation products (COPS) in edible food products accelerated in the 1980s as gas chromatography and high performance liquid chromatography detection methods were improved. COPS have been found in several foods including liquid eggs and dried egg products, milk and milk products, meat and meat products, marine food products, and other processed foods. Compelling evidence demonstrates that several cholesterol oxides are cytotoxic, atherogenic, mutagenic, and carcinogenic. Therefore, the presence of COPS in foods raises questions about the safety of consumption of some products.     

加工鸭蛋蛋黄脂类变化的GC分析

本研究用甲醇和氯仿,使蛋黄液从一相系统转变成二相系统来提取鸭蛋中的脂类,并将脂肪甲基化,用100m×0.25mm的GC毛细管柱来测定脂类中脂肪酸的组成。气相测定结果表明,蛋黄脂肪中C16:0、C18:0、C18:1-11c、C18:2-9c,12c以及C20:3n-3的含量较高;与鲜蛋相比,生和熟的咸蛋在脂肪酸种类上没有明显的变化,但出现了C11:0和C15:0两个饱和脂肪酸。鲜蛋、生熟咸蛋在不饱和脂肪酸含量逐渐减少,分别为67.07%、66.72%、64.68%。表明加工的步骤越多,其蛋黄中的不饱和酸被破坏程度越高。鸭蛋黄通过气相分析发现含有对人体有益的多不饱和脂肪酸如DHA和EPA等。     

Influence of Dietary Supplementation with α-Tocopheryl Acetate and Canthaxanthin on Cholesterol Oxidation in ω3 and ω6 Fatty Acid-enriched Spray-dried Eggs

ABSTRACT: The effect of feeding laying hens linseed oil or sunflower oil, with and without α-tocopheryl acetate and/or canthaxanthin, was evaluated on cholesterol oxidation in spray-dried whole egg at various storage periods. Storage of spray-dried eggs at room temperature in the dark resulted in an increase in cholesterol oxidation products from 18.1 μg/g, after spray drying, to 39.3 μg/g, at 12 mo of storage. No differences were found with either dietary oil or canthaxanthin supplementation. However, α-tocopheryl acetate supplementation resulted in a lower formation of cholesterol oxidation products during storage. No synergistic effect between α-tocopherol and canthaxanthin was detected.     

Cholesterol Oxides in Swedish Foods and Food Ingredients: Fresh Eggs and Dehydrated Egg Products

Cholesterol oxides were enriched from lipid extracts of fresh and dehydrated egg yolk products by chromatography on Lipidex and TEAP-Lipidex. Appropriate fractions from TEAP-Lipidex were analyzed by capillary GLC as their TMS derivatives. At the detection limit level, ca 0.2 ppm in total lipids, no cholesterol oxides could be detected in fresh egg yolk. Similarly, spray dried egg yolk powder contained only traces of cholesterol oxides when fresh or stored for 2 months at 4°C. Prolonged storage gave lipid extracts which contained variable levels (0.2–12 ppm) of known oxidation products, viz., cholest-5-ene-3β, 7α-diol, cholest-5-ene-3β, 7β-diol, 5,6α-epoxy-5α-cholestan-3β-ol, 5,6 β-epoxy-5 β-cholestan-3β-01, cholest-5-ene-3β, 20α-diol, 3 β-hydroxycholest-5-en-7-one. Traces or small quantifiable amounts of cholest ?5-ene-3β, 25-diol and 5α-cholestane-3β, 5, 6β-triol were observed in some samples at longer storage periods.     

褐壳与绿壳鸡胚蛋特色营养物质的含量变化

根据比色法原理,采用酶标仪对2 个品种鸡胚蛋中的胆固醇、卵磷脂、VE含量进行测定。与0胚龄相比,胆固醇呈明显下降趋势,5～12胚龄降幅最大,12胚龄后保持稳定;卵磷脂含量无显著性变化;VE含量逐渐增加,到12胚龄均增加了4 倍,之后保持稳定。2 个品种相比,入孵前绿壳蛋中胆固醇含量为褐壳蛋的79.37%,极显著低于褐壳蛋（P＜0.01）;孵化至12胚龄后,2 个品种的胆固醇含量差异不显著（P＞0.05）;绿壳蛋中的VE无论是在入孵前还是在孵化后期均极显著高于褐壳蛋（P＜0.01）;绿壳鸡胚蛋中的卵磷脂含量与褐壳蛋相比差异不显著（P＞0.05）。总体看来,随着孵化日龄的增加,2 个品种鸡胚蛋中的同种营养成分的变化趋势一致;在12胚龄后胆固醇大大降低,VE含量显著增加,且卵磷脂含量丰富,具有更高的食用价值。     

Cholesterol Oxidation in Fish and Fish Products

Fish and fish products are important from a nutritional point of view due to the presence of high biological value proteins and the high content of polyunsaturated fatty acids, especially those of the n‐3 series, and above all eicosapentaenoic acid and docosahexaenoic acid. However, these important food products also contain significant amounts of cholesterol. Although cholesterol participates in essential functions in the human body, it is unstable, especially in the presence of light, oxygen, radiation, and high temperatures that can cause the formation of cholesterol oxidation products or cholesterol oxides, which are prejudicial to human health. Fish processing involves high and low temperatures, as well as other methods for microbiological control, which increases shelf life and consequently added value; however, such processes favor the formation of cholesterol oxidation products. This review brings together data on the formation of cholesterol oxides during the preparation and processing of fish into food products which are recognized and recommended for their nutritional properties.     

Lipid and Cholesterol Oxidation in Whole Milk Powder during Processing and Storage

The influence of animal feed quality on lipid and cholesterol oxidation in whole milk powder was investigated. Powders from a herd receiving a ‘supplemented’ diet showed reduced PV (p < 0.01) and TBARS (p < 0.09) compared to a ‘restricted’ herd, after storage in both vacuum and sachet-packs and less (p < 0.003) cholesterol oxidation products (COPs). High pre-heating temperatures resulted in higher levels of PV, TBARS and COPs in fresh whole milk powders than low pre-heat temperatures, but after storage the reverse occurred. Superior animal feed quality and proper control of processing and storage conditions enhanced oxidative stability of whole milk powder. Lipid and cholesterol oxidation were positively correlated (p < 0.001).     

不同饲料喂养鸡蛋中胆固醇的含量测定

对A,B,C,D四组不同饲料喂养新鲜鸡蛋的胆固醇含量进行测定,比较鸡蛋的平均重量、蛋清相对重量、蛋黄相对重量、蛋壳相对重量、蛋壳厚度.筛选出胆固醇含量较低的营养保健型鸡蛋.结果表明:A、B组的胆固醇含量偏高.C和D组的胆固醇含量较低,所有其他检测指标基本上没有差异.综合营养和经济因素,D组的鸡蛋更适宜于加工生产.     

高效液相色谱法测定食品中的胆固醇

本文建立了高效液相色谱法测定动物性食品中胆固醇的含量,确定的色谱条件如下:C18色谱柱,二极管阵列检测器,205nm检测波长,100%甲醇作为流动相,1．0ml/min流速。该方法的精密度RSD小于5%,回收率大于96%～102%。在此色谱条件下15min内完成了胆固醇的分离,结果比较理想。研究表明此新建方法准确而快速,并能适用于绝大部分食品中胆固醇的测定。     

Nitrogen Oxide-Initiated Cholesterol Oxidation and Carotenoid Degradation in an Egg Lipid Model System

The influence of nitrogen oxide (NO _x ) concentrations on the oxidation of cholesterol and carotenoids in an egg lipid model system was investigated. The effects of dietary α-tocopherol supplementation on cholesterol and carotenoid stability in egg lipids were also evaluated. The rate constants for cholesterol oxidation and carotenoid degradation in egg lipids during storage at 40°C were affected by both the egg treatments and the level of exposure to NO _x before storage. The presence of NO _x greatly promoted the oxidation of cholesterol and carotenoids. Dietary supplementation with α-tocopherol greatly improved the stability of carotenoids and cholesterol in egg lipids exposed to NO _x . The addition of carotenoids to egg lipids also protected cholesterol from NO _x -initiated oxidation. The patterns of cholesterol oxidation and carotenoid loss in this lipid model system were similar to those in egg powders processed by the direct gas-fired spray-dryer.     

Cholesterol Oxidation Products in Some Muscle Foods

Cholesterol oxidation products were estimated in some meat products by capillary gas chromatography after trimethylsilylation. Peak identities were confirmed by mass spectrometry. Freeze-dried pork, stored in contact with air at 22°C for ca. 3 yr, revealed 7α- and 7β-hydroxycholesterol, 7-ketocholesterol, α- and β-epoxide and cholestane-triol. The total concentration of oxidation products reached almost half of the remaining cholesterol content with 7-ketocholesterol as the predominant species. Some oxidation products were noted at a few ppm levels in broiled beef steaks, but not in precooked beef products. As rancidity development advanced in comminuted and cooked meats during storage, the oxidation of cholesterol became apparent.     

直接皂化比色法测定食品中胆固醇的研究

研究利用氢氧化钾 甲醇溶液在 80℃水浴中对食品样品 (蛋黄粉和奶粉 )直接皂化30min ,并在皂化混合物中使用抗氧化剂 ,然后用正己烷萃取并离心 ,取出一定量正己烷层挥发干后 ,用FeSO4 冰乙酸 浓硫酸作显色剂在 4 90nm下测定胆固醇含量。该方法具有良好的线性 ,与气相色谱法测定的结果差异不显著。这为今后在生产和科研中快速准确地测定食品中胆固醇含量提供了有效手段。     

Quantification of Cholesterol Oxidation Products In Egg Yolk Powder Spray-dried with Direct Heating

A direct-heated spray dryer with an evaporative capacity of up to 7 kg H₂O/hr was used to identify processing conditions responsible for formation of cholesterol oxidation products (COPS) in spray-dried egg yolk. Outlet air temperature and nitrogen oxides (NO_x) in the combustion gases were the only conditions that affected COPS levels. At outlet temperature 150°C, total COPS concentrations in the spray-dried product were 75 ppm at 5 ppm NO_x and 213 ppm at 300 ppm NO_x. In products dried at 75°C outlet temperature, total COPS concentrations were 21 ppm at 5 ppm NO_x and 58 ppm at 300 ppm NO_x. In general, individual COPS responded to outlet temperature and NO_x in the same manner as total COPS.     

Cholesterol and Lipid Oxidation Products in Cooked Meat as Affected by Raw-Meat Packaging and Irradiation and by Cooked-Meat Packaging and Storage Time

Aerobic packaging significantly increased cholesterol oxidation products (COPs) and thiobarbituric acid reactive substances (TBARS) in cooked turkey, pork, and beef patties after 7‐d storage, but vacuum packaging was very effective in preventing cholesterol and lipid oxidation. Packaging of meat after cooking had a much stronger effect on COPs formation than before cooking, and irradiation had only a minor effect. The amount of total COPs correlated well with TBARS in cooked meat. Turkey had the highest rates of COPs and TBARS formation and beef had the lowest rates after 7‐d storage, which were closely related to the fatty acid composition of meats. 7a‐hydroxycholesterol, 7p‐hydroxycholesterol, and 7‐ketocholesterol were the major COPs detected in all 3 cooked meat patties.     

气相色谱法同时测定食品中的胆固醇和植物甾醇

建立气相色谱法同时测定食品中植物甾醇和胆固醇含量的分析方法,测定植物甾醇含量较高的常见植物油和同时含有胆固醇及植物甾醇的样品。采用5α-胆甾烷为内标参照物,样品经皂化后提取,浓缩后正庚烷定容上机进样分析。胆固醇和植物甾醇在0.001～2.5 mg/mL质量浓度范围内线性良好,线性相关系数R2均大于0.99。方法的检出限为0.3 mg/100 g,定量限为1.0 mg/100 g,该方法相较于液相色谱法能有效将胆固醇和植物甾醇进行分离,具有步骤简单、重复性好、准确度和灵敏度高等特点。     

Differential Inhibitory Effect of alpha-, beta-, gamma-, and delta-Tocopherols on the Metal-Induced Oxidation of Cholesterol in Unilamellar Phospholipid-Cholesterol Liposomes

ABSTRACT: Cholesterol oxidation products (COPs) are present in biological tissues and in foods. The inhibitory effect of antioxidants, such as tocopherols, on COPs formation has been only partially investigated. The antioxidant effect of dl alpha-, dl beta-, dl gamma-, and dl-delta tocopherol on the metal-induced oxidation of phosphatidylcholine (PC): cholesterol liposomes was assayed. Formation during liposome oxidation of six different COPs was monitored by gas chromatography. dl alpha-, and dl gamma-tocopherol show good inhibitory effect against PC-fatty acid oxidation and also on COPs formation. dl delta-Tocopherol is less effective than the alpha-and gamma-homologous, beta-tocopherol being unable to prevent PC and cholesterol oxidation. dl alpha-, and dl gamma-Tocopherol are more effective to prevent the oxidation of the lateral chain of cholesterol molecule. At the highest tocopherol concentration assayed, dl alpha-tocopherol shows prooxidant effect, enhancing liposomal oxidation and COPs formation. It is concluded that the tocopherols assayed can inhibit cholesterol oxidation but to a different degree.     

禽蛋中胆固醇的酶催化分光光度测定法研究

本实验建立一种禽蛋中胆固醇含量快速测定方法--酶催化分光光度法。禽蛋匀浆液由直接皂化法处理,经酶工作液催化后,用分光光度法于波长500nm 处测定其含量。方法回收率均在90% 以上,变异系数均低于4%,线性范围20～600mg/ml,具有良好的准确度与精密度,适合禽蛋中胆固醇含量的快速测定。     

Effect of Antioxidants on Cholesterol Oxidation in Spray-dried Egg Yolk during Extended Ambient Storage

ABSTRACT: Equimolar amounts of butylated hydroxyanisole, ascorbyl palmitate or a tocopherol blend were added to liquid yolk and spray-dried. One-g samples were stored in the dark at ambient temperature for 36 mo, then evaluated using gas chromatography. The tocopherol blend and BHA inhibited 7-ketocholesterol production. No significant differences were observed between the control and the various antioxidant treatments for the production of other cholesterol oxides. In contrast to the results of a previously conducted accelerated study, the added antioxidant levels were insufficient to significantly reduce cholesterol oxidation in spray-dried egg yolk held for an extended period of time, and additional means of inhibition may be required.     

溶血磷脂制备含胆固醇微乳液的研究

溶血磷脂HLB较大，易形成O／W型乳化剂，可制备热力学稳定的微乳化体系。利用溶血磷脂作乳化剂，制备含胆固醇的微乳液，是以胆固醇为油相，溶血磷脂为乳化剂，正丙醇为共表面活性剂，制成微乳液。最终产物呈透明或半透明的均相混合物。