Fatty acid composition, conjugated linoleic acid isomers and cholesterol in beef from crossbred bullocks intensively produced and from Alentejana purebred bullocks reared according to Carnalentejana-PDO specifications

The purpose of this study was to characterise and compare the nutritional value of Portuguese Carnalentejana-PDO beef, obtained from Alentejana purebred bullocks reared in a semi-extensive system, with the meat from Alentejana×Charolais crossbred bullocks produced in a conventional intensive concentrate-based system. In addition, seasonal changes in Carnalentejana-PDO beef quality were assessed, by analysing meat samples from animals slaughtered in early autumn and late spring. The results showed that beef-PDO has different intramuscular fat characteristics in comparison with meat from crossbred bullocks fed intensively with concentrate. However, the finishing period of Alentejana purebred bullocks with concentrate seems to attenuate most of the typical grass-fed characteristics of meat fat. Nevertheless, from a human nutrition perspective, Carnalentejana-PDO beef seems to be healthier than that from intensively reared animals since it has a lower n-6/n-3 ratio, although always above the recommended guidelines for human diet, and higher proportions of c9,t11 conjugated linoleic acid (CLA) isomer and total CLA relative to saturated fatty acids plus total cholesterol (CLA/SFA+CHR). Furthermore, no seasonal variation in the nutritional quality of beef-PDO was apparent. Taken together, the data indicate that Carnalentejana-PDO beef is of greater nutritional value than intensively produced beef from crossbred bullocks throughout the year.     

Removal of cholesterol by lactobacilli via incorporation and conversion to coprostanol

Fifteen strains of Lactobacillus and Bifidobacterium were screened based on their ability to adhere to hydrocarbons via the determination of cellular hydrophobicity. Lactobacillus acidophilus ATCC 314, L. acidophilus FTCC 0291, Lactobacillus bulgaricus FTCC 0411, L. bulgaricus FTDC 1311, and L. casei ATCC 393 showed greater hydrophobicity and, thus, were selected for examination of cholesterol-removal properties. All selected strains showed changes in cellular fatty acid compositions, especially total fatty acids and saturated and unsaturated fatty acids in the presence of cholesterol compared with those grown in the absence of cholesterol. In addition, we found that cells grown in media containing cholesterol were more resistant to sonication and enzymatic lysis compared with those grown without cholesterol. We further evaluated the location of the incorporated cholesterol via the insertion of fluorescence probes into the cellular membrane. In general, enrichment of cholesterol was found in the regions of the phospholipid tails, upper phospholipids, and polar heads of the cellular membrane phospholipid bilayer. Our results also showed that lactobacilli were able to reduce cholesterol via conversion of cholesterol to coprostanol, aided by the ability of strains to produce cholesterol reductase. Our results provided experimental evidence to strengthen the hypothesis that probiotics could remove cholesterol via the incorporation of cholesterol into the cellular membrane and conversion of cholesterol to coprostanol. The strains studied may be potential health adjunct cultures in fermented dairy products with possible in vivo hypocholesterolemic effects.     

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.     

Effect of the Lycium barbarum polysaccharides administration on blood lipid metabolism and oxidative stress of mice fed high-fat diet in vivo

Epidemiological and experimental studies have suggested that high dietary fat intake of mice is associated with many physically degenerative diseases. Since oxidative stress and abnormal lipid metabolism have been speculated to be critical mechanisms underlying degenerative diseases, we hypothesized that a high-fat (HF) diet might induce oxidative stress or lipid oxidation and subsequently contribute to the high risk of some diseases such as cardiovascular and cerebrovascular ones. To test this hypothesis, male kunming mice were placed on either a HF diet or a normal laboratory diet for 30 consecutive days. This investigation demonstrated that blood fat [low density lipoprotein (LDL), total cholesterol (TC), triacylglycerols (TAG), high density lipoprotein (HDL)], blood sugar (blood glucose and liver glycogen) and oxidative stress (activities of antioxidant enzymes and levels of non-enzymic antioxidants) of mice fed high-fat diet (group II) were significantly increased or decreased (P < 0.05, P < 0.01) when compared with the control group (I). The present study revealed that HF diet induced oxidative stress and provided novel evidence regarding the link between high dietary fat and increased risk of degenerative diseases. The administration of Lycium barbarum polysaccharides did not show any effect on the body weight of the experimental mice, but significantly decreased the levels of LDL, TC, TAG, blood glucose and thiobarbituric acid reactive substances (TBARS) or increased the activities of antioxidant enzymes (P < 0.05, P < 0.01) when compared with mice in HF group (II). These findings were further supported by significantly increased non-enzymic antioxidants levels (P < 0.05, P < 0.01), suggesting that L. barbarum polysaccharides showed a noticeable inhibition against lipid oxidation induced by free radicals caused by HF diet intake (groups III, IV, V) on the basis of their antioxidant activities.     

乳酸菌降胆固醇机制的研究进展

乳酸菌作为益生菌的主要来源,对宿主健康具有一定的促进作用,尤其是降低胆固醇作用已成为近年来的研究热点。在过去的半个世纪,人们已筛选到多种能降低胆固醇的乳酸菌种属,如乳杆菌属、双歧杆菌属和肠球菌属菌株,并且这些菌株的降胆固醇能力,大部分已通过动物或人体试验证实,但作用机制尚不明晰。文中综述了半个世纪以来乳酸菌降胆固醇机制研究的进展,并针对目前存在的问题加以展望,旨在为乳酸菌的深入研究与开发提供参考。     

Simultaneous HPLC quantification of total cholesterol,tocopherols and β-carotene in Barrosã-PDO veal

A simple, rapid and sensitive procedure for the simultaneous determination of total cholesterol, tocopherols and β-carotene in meat is described. The method involves a direct saponification of the meat, a single n-hexane extraction and the analysis of the extracted compounds by normal-phase HPLC, using fluorescence (tocopherols) and UV–Vis photodiode array (cholesterol and β-carotene) detections in tandem. Rates of recovery of spiked meat samples were 93% for cholesterol, 83–86% for (α-, β- and -γ) tocopherols and 89% for β-carotene. Repeatabilities were high (CV < 6%) for all determined compounds, except for δ-tocopherol. This tocopherol, which is not usually present in meat, showed a much lower recovery percentage (73%) and repeatability (12.8%). This methodology was applied for the quantification of total cholesterol, tocopherols and β-carotene in three muscles (longissimus thoracis, longissimus lumborum and semitendinosus) of the Portuguese traditional Barrosã-PDO veal, obtained from autochthonous calves fed extensively during summer (with the least abundant green pastures) and slaughtered in early autumn (October). Barrosã-PDO veal showed median contents of total cholesterol (0.50–0.56 mg/g) and, depending on the analysed muscle, moderate to high contents of α-tocopherol (3.3–3.9 μg/g) and β-carotene (0.07–0.09 μg/g), suggesting an high sensorial and hygienic quality.     

大豆蛋白降胆固醇作用最佳剂量探讨

目的:探讨大豆蛋白降胆固醇作用适宜剂量。方法:4周龄健康雄性Wistar大鼠经2w诱发高血胆固醇后,将32只大鼠随机分为4组,分别给予10%大豆蛋白、15%大豆蛋白、20%大豆蛋白和20%酪蛋白,4w后采血测定血清TC、TG、HDL-C和LDL-C浓度。数据用SPSS统计软件进行方差分析。结果:经2w诱导高脂模型后,高胆固醇模型大鼠的TC浓度是阴性对照组的2.7倍。给以处理因素4w后,与20%酪蛋白组相比,15%和20%大豆蛋白组大鼠血清TC降低,但无统计学意义;15%大豆蛋白组大鼠血清TC、HDL-C和LDL-C浓度显著低于10%大豆蛋白组(P0.05);20%大豆蛋白组大鼠血清TG浓度显著低于10%大豆蛋白组(P0.05)。结论:4w内15%大豆蛋白和20%大豆蛋白具有相同的降低血浆胆固醇的趋势,10%大豆蛋白无降低胆固醇的作用。     

国产血清胆固醇试剂盒测定蛋黄胆固醇的研究

以两种国产血清胆固醇酶法试剂盒(Ⅰ、Ⅱ)测定蛋黄胆固醇含量,评价用血清胆固醇试剂盒测定食品胆固醇的可行性。并将此法与国家标准方法(Feng法)进行比较。其结果是:试剂盒Ⅰ在胆固醇409μg/管,粗脂肪8878μg/管范围内线性良好,rⅠ=0.9999,YⅠ=0.00390X+0.0040;试剂盒Ⅱ在胆固醇205μg/管,粗脂肪4439μg/管内线性良好,rⅡ=0.9994,YⅡ=0.00414X-0.0005。批内变异:C·VI=3.286%,C·VⅡ=3.774%,批间变异:C·VⅠ=4.157%,C·VⅡ=4.906%;回收率:Ⅰ为97.6～104.0%,Ⅱ为98.38～104.9%。试剂盒法与国标法相关良好;rⅠ=0.9972,YⅠ=1.049X-2.083;rⅡ=0.9989,YⅡ=0.9984X-0.6266。试剂盒酶法比国标法省略了皂化,再萃取,再抽干和试剂配制的步骤,而且可以避免强酸伤害人体和腐蚀仪器。     

植物甾醇的研究进展与趋向(Ⅱ)——植物甾醇的应用基础和开发研究

阐述了当前关于植物甾醇应用基础研究的两个关键问题 ,简述了植物甾醇的开发和应用研究现状。