激光对生产β-胡萝卜素的藻种——盐生杜氏藻(Dunaliella salina)诱变的研究

用激光(335nm,0.014MW/mm~2)对产生6-胡萝卜素的盐生杜氏藻(Dunaliella Salina)进行了诱变研究,藻的存活率为90％。诱导后筛选到三个盐生杜氏藻的品系。生长速度较原藻最高增加20％,长度增加7.5％,萨-胡萝卜素生产能力为0.48mg·100ml~(-1)天~-1),比原藻增加19％。     

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.     

Inhibition of oxidation in 10% oil-in-water emulsions by β-carotene with α- and γ-tocopherols

The effects of low concentrations of β-carotene, α-, and γ-tocopherol were evaluated on autoxidation of 10% oil-in-water emulsions of rapeseed oil triacylglycerols. At concentrations of 0.45, 2, and 20 μg/g, β-carotene was a prooxidant, based on the formation of lipid hydroperoxides, hexanal, or 2-heptenal. In this emulsion, 1.5, 3, and 30 μg/g of γ-tocopherol, as well as 1.5 μg/g of α-tocopherol, acted as antioxidants and inhibited both the formation and decomposition of lipid hydroperoxides. Moreover, at a level of 1.5 μg/g, γ-tocopherol was more effective as an antioxidant than α-tocopherol. At levels of 0.5 μg/g, both α- and γ-tocopherol significantly inhibited the formation of hexanal but not the formation of lipid hydroperoxides. Oxidation was effectively retarded by combinations of 2 μg/g β-carotene and 1.5 μg/g γ- or α-tocopherol. The combination of β-carotene and α-tocopherol was significantly better in retarding oxidation than α-tocopherol alone. While γ-tocopherol was an effective antioxidant, a synergistic effect between β-carotene and γ-tocopherol could not be shown. The results indicate that there is a need to protect β-carotene from oxidative destruction by employing antioxidants, such as α- and γ-tocopherol, should β-carotene be used in fat emulsions.     

Thraustochytrid as a potential source of carotenoids

Thraustochytrids, marine protists whose dominant genera are Thraustochytrium and Schizochytrium, belong to the kingdom Chromista and are known as an industrial source of DHA. We describe here that thraustochytrid strain KH105, isolated as a DHA producer, also accumulates significant levels of β-carotene and xanthophylls including canthaxanthin and astaxanthin. A4-d cultivation using a medium composed of 10% glucose and less than 0.3% of nitrogen sources in a half-concentration of seawater gave an astaxanthin production up to 6.1 mg/L, and canthaxanthin content reached more than 10 mg/L under conditions where a higher concentration of nitrogen sources (6%) was employed. It might be advantageous in mass production systems for these carotenoids to be extracted readily by simply suspending the cells with organic solvents such as acetone and chloroform. Analyses on the morphological and life history features of the KH105 strain revealed that it belongs to the genus Schizochytrium. This particular species of thraustochytrids is thus considered to be a promising source of xanthophylls as well as DHA for use in the food industry.     

大分子乳化剂稳定的纳米乳中β-胡萝卜素的降解

分别以乳清分离蛋白、热处理乳清分离蛋白、乳清分离蛋白与麦芽糖糊精的混合物和美拉德反应复合物为乳化剂,制备β-胡萝卜素纳米乳,并考察其乳滴粒径分布及β-胡萝卜素的降解。结果表明：乳清分离蛋白与麦芽糖糊精共价复合后,形成的纳米乳液平均粒径更小,但复合物加速纳米乳中β-胡萝卜素的降解。而热处理乳清分离蛋白能显著抑制纳米乳中β-胡萝卜素的降解,其机制可能是蛋白质大分子聚集体的形成对β-胡萝卜素起保护作用。     

Characterization of Inhibitory Capability on Hyperpolarization-Activated Cation Current Caused by Lutein (β,ε-Carotene-3,3′-Diol), a Dietary Xanthophyll Carotenoid

Lutein (β,ε-carotene-3,3′-diol), a xanthophyll carotenoid, is found in high concentrations in the macula of the human retina. It has been recognized to exert potential effectiveness in antioxidative and anti-inflammatory properties. However, whether and how its modifications on varying types of plasmalemmal ionic currents occur in electrically excitable cells remain incompletely answered. The current hypothesis is that lutein produces any direct adjustments on ionic currents (e.g., hyperpolarization-activated cation current, I_h [or funny current, I_f]). In the present study, GH₃-cell exposure to lutein resulted in a time-, state- and concentration-dependent reduction in I_h amplitude with an IC₅₀ value of 4.1 μM. There was a hyperpolarizing shift along the voltage axis in the steady-state activation curve of I_h in the presence of this compound, despite being void of changes in the gating charge of the curve. Under continued exposure to lutein (3 μM), further addition of oxaliplatin (10 μM) or ivabradine (3 μM) could be effective at either reversing or further decreasing lutein-induced suppression of hyperpolarization-evoked I_h, respectively. The voltage-dependent anti-clockwise hysteresis of I_h responding to long-lasting inverted isosceles-triangular ramp concentration-dependently became diminished by adding this compound. However, the addition of 10 μM lutein caused a mild but significant suppression in the amplitude of erg-mediated or A-type K⁺ currents. Under current-clamp potential recordings, the sag potential evoked by long-lasting hyperpolarizing current stimulus was reduced under cell exposure to lutein. Altogether, findings from the current observations enabled us to reflect that during cell exposure to lutein used at pharmacologically achievable concentrations, lutein-perturbed inhibition of I_h would be an ionic mechanism underlying its changes in membrane excitability.     

β-胡萝卜素乳液的制备及其稳定性比较

以吐温80和变性淀粉为乳化剂,将β-胡萝卜素制成水溶性乳液,比较两种乳化剂制备乳液的光、热稳定性。结果发现,两种乳液在光照条件下稳定,但对热的稳定性有一定差异,吐温80制备的乳液热稳定性较差。显微照片和乳液粒径分布可知,吐温80乳液较纯胶乳液稳定。     

A simple UV-Vis spectrophotometric method for determination of β-carotene content in raw carrot, sweet potato and supplemented chicken meat nuggets

A simple, rapid and low cost analytical method for the determination of β-carotene content in four different food categories is developed and validated. This method is based on solvent extraction followed by UV-Vis spectrometric detection. Target compound was extracted with four different solvents, in which acetone appears to be an excellent extractant as recovery of the analyte at 1 μg/g concentration in spiked samples was in the range of 67.8-98.8%, with relative standard deviation (RSD) ranging between 4.8 and 6.6%. Intra- and inter-day assay precisions of the method at 0.1, 1.0 and 5.0 μg/g concentrations ranged in between 3.4 and 8.9%. The linearities for β- carotene in the pure acetone, raw carrot, sweet potato, and fortified raw and cooked chicken meat nuggets were 0.994, 0.995, 0.990, 0.984 and 0.984, respectively. For robustness, the analytical method was applied to 24 samples of four different food categories namely carrot, sweet potato and carrot and sweet potato supplemented chicken meat nuggets.     

类胡萝卜素在癸酸反胶束溶液中的电子吸收光谱特征变化

采集3种类胡萝卜素在癸酸反胶束溶液中的电子吸收光谱,进行特征分析。用四氢呋喃、丙酮和乙醇3种组装助剂分别构建癸酸反胶束溶液,番茄红素（开环碳氢化合物）、β-胡萝卜素（具环碳氢化合物）和玉米黄素（具环羟基化合物）分别溶解在其中后,采集各溶液在300～550 nm波长范围内的电子吸收光谱,分析其特征。结果表明：与3种类胡萝卜素在癸酸中的光谱特征相比,它们在癸酸反胶束溶液中的最大吸收波长（λmax）均有微小位移;具环类胡萝卜素的λmax发生红移,开环胡萝卜素的λmax发生紫移;同时,助剂极性的增强可使三者的吸光系数（A1%1 cm）减小。