油橄榄叶多糖的提取工艺优化及其理化性质和抗氧化活性

为增加油橄榄叶多糖的开发利用价值,以油橄榄叶为实验材料,采用正交试验优化油橄榄叶多糖(OLP)的提取工艺,高效凝胶渗透色谱-多角度激光光散射仪联用(HPGPC-MALLS)测定分子量,PMP柱前衍生高效液相色谱法分析OLP的单糖组成,并评价其抗氧化活性。结果显示,OLP的最佳提取工艺条件为料液比1:27.5g/mL,温度95℃,提取时间3.5 h,在此条件下OLP的得率为2.75%;OLP的重均分子量(Mw)为25.36 kDa,数均分子量(Mn)为19.32 kDa,多分散系数为1.313;OLP主要由葡萄糖(Glc)、半乳糖(Gal)和氨基半乳糖(GalN)组成,还含有鼠李糖(Rha)、阿拉伯糖(Ara)、木糖(Xyl)、甘露糖(Man)和氨基葡萄糖(GlcN)等单糖,各单糖的相对摩尔比为56.2:15.9:10.3:8.3:5.9:2.6:0.5:0.3;抗氧化活性实验结果发现,OLP具有较好的抗氧化活性,对羟自由基、超氧阴离子自由基和DPPH自由基的半数抑制浓度(IC₅₀)分别为0.422、0.302和0.268 mg/mL。本研究所得油橄榄叶多糖的提取工...     

不同生长期黄芪无机元素动态特征分析

目的:探究不同生长期黄芪中Mg、Ca、V、Mn、Fe、Co、Ni、Cu、Zn、Ba这10种无机元素的含量差异与动态积累特征,从无机元素层面对黄芪适宜采收期的确定提供帮助。方法:收集不同生长期黄芪样品,采用电感耦合等离子体质谱法测定其元素含量,并结合单因素方差分析、主成分分析（PCA）、正偏最小二乘判别分析（OPLS-DA）和相关性分析方法分析黄芪药用部位生长过程中无机元素的变化及积累规律。结果:不同生长期黄芪10种元素含量差异较大,Mg、Ca、V、Mn、Fe、Ni、Cu、Co元素均在10月份时含量达到最大值,Ba在6月份时含量达到最大值,8月为上述元素含量最小值时的生长期,Zn元素在9月的含量显著高于其他生长期,7月时含量显著低于其他生长期（P<0.05）,10种元素含量均为先降后升的动态变化趋势。相关性分析结果表明:V与Ca、Fe;Ni与Ba元素之间均存在极显著性相关关系（P<0.01）,主成分分析综合得分结果表明10月份黄芪样品得分排名第一,正偏最小二乘判别分析表明Zn、Ni、Cu、V四种元素为鉴别不同生长期黄芪的主要特征元素。结论:黄芪中无机元素含量与其生长期密切相关,无机元素可以作为黄芪采收期确定的指标之一。综合分析,10月中下旬为黄芪药材的最佳采收期。     

Distribution,stability, and protein interactions of Aflatoxin M1 in fresh cheese

Aflatoxin M₁ (AFM₁), a metabolite resulting from the hepatic metabolism of aflatoxin B₁, is a potential carcinogen that can be found in milk, cheese, and others dairy products. In this work, we aimed to elucidate the distribution and fate of AFM₁ in fresh cheese and whey during cheese manufacturing and storage as well as the level of interaction of this toxin with various milk, cheese, and whey proteins. Additionally, we analyzed the in vitro behavior of casein, α-lactalbumin, β-lactoglobulin, bovine serum albumin (BSA), lactoferrin, and mixtures thereof, with a fixed concentration of AFM₁ after covalent crosslinking. Our results show that up to 70% of the AFM₁ levels present in milk spiked with 0.5 and 1.5 μg L⁻¹ are released in whey during fresh cheese manufacturing. The whey and milk proteins with more AFM₁ molecules bound were α-lactalbumin and casein, with 88% and 81%, respectively. We also observed a substantial decrement in AFM₁ concentration during ripening that correlated inversely with plate counts of lactic acid bacteria and directly with the whey-draining process that occurs during fresh cheese maturation or storage. This knowledge may serve as a basis for interventions in the dairy industry aiming to increase the security of cheese and other dairy products.     

中国沙棘雄花花被和花粉蛋白质营养评价

目的 分析中国沙棘雄花花被及花粉蛋白质含量和氨基酸组成及其营养均衡性。方法 采用凯氏定氮法和柱后衍生阳离子交换色谱方法分析中国沙棘雄花花被及花粉中蛋白质和氨基酸的含量,并结合国际上通用的营养价值评价方法对其蛋白质含量、化学评分(chemical sore, CS)、氨基酸评分(aminoacid score, AAS)、必需氨基酸指数(essential amino acid index, EAAI)、氨基酸比值系数分(score of ratio coefficient of amino acid,SRCAA)、生物价(biological value, BV)和营养指数(nutritional index, NI)等进行综合评价。结果 中国沙棘雄花花被及花粉蛋白质含量分别为16.07%、20.45%;中国沙棘雄花花被及花粉中氨基酸含量无显著差异, 17种氨基酸总含量分别为13.59 g/100 g、17.06 g/100 g;蛋白质营养评价表明,中国沙棘雄花花被及花粉中总必需氨基酸分别为31.14g/100g、33.10g/100g,接近于联合国粮农组织与世界卫生组织(Foodan...     

Seasonal variation of aflatoxin M1 contamination in industrial and traditional Iranian dairy products

This study aimed to determine the occurrence of aflatoxin M₁ (AFM₁) contamination in 682 dairy product samples consisting of raw milk of cow, goat and sheep; Lighvan cheese; and industrial and traditional yoghurt, Kashk and Doogh samples collected from popular markets and dairy ranches in four large Iranian cities. Thin layer chromatography (TLC) technique was used for analysis of the samples. Results showed that the incidence and levels of AFM₁ contamination in raw cow milk and industrial products (manufactured from cow milk) were higher than raw goat or sheep milk, and traditional products (made from goat and sheep milk), respectively. Moreover, seasonal variations influenced the concentration of AFM₁ in most of the analyzed dairy products. Owing to the abundance and popularity of the industrial products, contamination of these products in such a level could be a potential hazard for public health.     

Effects of synthesis temperature on particle size/shape and photoluminescence characteristics of ZnS:Cu nanocrystals

ZnS:Cu nanocrystals are prepared by solution synthesis technique, and the optimum range of synthesis temperature and the particle size/shape for the high photoluminescence (PL) properties of ZnS:Cu nanocrystals are investigated in this study. With an increase of synthesis temperature, the crystal structure is not changed. However, the particle size increases slightly. PL intensity is maximum for the sample prepared at 85 °C for the temperature range used in this study (70–95 °C). This is the first observation for the ZnS:Cu nanocrystals prepared by solution synthesis technique. The X-ray photoelectron spectroscopy (Cu2p_3/2), performed to explain this phenomenon, demonstrates that with lower synthesis temperature (<85 °C), Cu acts as the normal accepter dopant, leading to the high PL intensity. With higher temperature (>90 °C), however, Cu is transformed into CuO, and CuO acts as the nonradiative recombination center, resulting in the substantial decrease of PL intensity observed in this study.     

Two year survey on the occurrence and seasonal variation of aflatoxin M1 in milk and milk products in Serbia

The incidence of contamination of aflatoxin M1 (AFM1) in milk and milk products samples collected in Serbia was investigated by using the competitive enzyme linked immunosorbent assay (ELISA) technique. A total of 1438 samples composed of 678 raw milk, 438 heat treated milk and 322 milk product samples that were analyzed during the period of 2013–2014, including all seasons. The AFM1 levels exceeded the European Union maximum residue permitted amount (EU MRL) in 56.3% raw milk, 32.6% heat treated milk and 37.8% of milk product samples. Milk powders had the highest mean AFM1 concentration (0.847 μg/kg) of all types of milk products examined. Mean concentration of AFM1 in raw milk samples during the period of winter in Serbia was 0.358 μg/kg and did not significantly differ from the mean concentrations of 0.375 μg/kg during the spring. However, the AFM1 raw milk concentration in the summer (0.039 μg/kg) and autumn season (0.103 μg/kg) was significantly lower. Seasonal variation of AFM1 concentrations in heat treated milk samples followed the trend observed in raw milk. Mean raw milk AFM1 concentration has dropped down by 10 fold from 0.314 μg/kg in 2013 to 0.035 μg/kg in 2014. The fraction of raw milk samples exceeding the EU MRL has decreased from 62.3% to 11.5% by the end of 2014.     

A survey of concentration of aflatoxin M1 in dairy products marketed in Turkey

The aim of this study was to examine the presence of aflatoxin M1 (AFM1) in dairy product samples by enzyme-linked immunosorbent assay (ELISA). Aflatoxin M1 were found in 135 (64%) out of 210 analyzed samples. Only 7% of dairy product samples were contaminated at levels above the legal limits. AFM1 was detected in 43 (86%) of milk samples (ranging from 1 to 30 ng/l), in 38 (63%) of cheese (ranging from 12 to 378 ng/kg), in 28 (56%) of yoghurt (ranging from 2.5 to 78 ng/kg) and in 26 (52%) of dairy dessert samples (ranging from 1.5 to 80 ng/kg). None of the raw milk samples contained levels above the Turkish legal limit. The AFM1 levels of 7(14%) yoghurt, 5 (10%) dairy dessert and 3 (5%) cheese samples were above the limits of the Turkish Food Codex. It is emphasized that the presence of AFM1 in dairy products may be regarded as a potential hazard for human health.