Quantitative analysis of acrylamide in tea by liquid chromatography coupled with electrospray ionization tandem mass spectrometry

An effective sample preparation procedure was optimized and a liquid chromatography–tandem mass spectrometry (LC–MS/MS) was developed for the quantitative analysis of acrylamide in tea. [¹³C₃]-acrylamide was used as internal standard. Acrylamide was extracted at 25 °C for 20 min by 10 ml water followed by 10 ml acetonitrile, and then 4 g of magnesium sulfate and 0.5 g of sodium chloride were added to the above mixture under stirring thoroughly. In order to increase the response of acrylamide, 9 ml acetonitrile layer was taken and concentrated to 0.5 ml. Solid-phase extraction with an Oasis MCX cartridge was carried out for clean-up. The limit of detection (LOD) and limit of quantification (LOQ) were 1 and 5 ng/ml, respectively. The recovery efficiency of the extraction procedure ranged between 74% and 79%. The levels of acrylamide in 30 tea samples were less than 100 ng/g. Black, oolong, white and yellow tea samples had quite low acrylamide contents (<20 ng/g). Higher acrylamide levels occurred in baked, roasted, and one sun-dried green tea samples (46–94 ng/g).     

松辽盆地长岭断陷龙凤山地区油气分布有序性及其主控因素

对于松辽盆地油气分布有序性的研究较为薄弱,其主控因素尚不明确,制约了该区的油气勘探进程。为此,以该盆地油气勘探新区——长岭断陷龙凤山地区为例,从油气藏类型、储量丰度、油气相态等方面刻画了该区油气分布的有序性,结合油气成藏条件划分出S2、S203和S201等3个油气运聚单元,并利用层次分析法对不同成藏要素的配置关系进行定量评价,明确了油气分布有序性的主控因素。研究结果表明:(1)自北部洼陷带向西部构造带,该区油气分布在相态上体现为气藏—油气藏—油藏的有序变化,油气藏类型上则表现为岩性油气藏、构造—岩性油气藏、岩性—构造油气藏、构造油气藏的渐变特征,油气富集程度上呈现出储量及其丰度逐渐增加的趋势;(2)该区油气分布有序性受控于3种因素,断—源时空配置的有效性控制了油气相态分布的有序性,不同运聚单元边界条件的差异性控制了油气藏类型分布的有序性,断—源—砂—盖配置的差异性则控制了油气富集程度的有序性。结论认为,S201运聚单元的油气成藏条件最为优越,源—断—砂—盖配置最好,勘探潜力最大,可作为下一步油气勘探的重点区块。     

玉米淀粉/蛋壳粉复合膜的制备及性能分析

以玉米淀粉（corn starch,CS）和蛋壳粉（eggshell powder,ESP）为主要成膜基材制备CS/ESP复合膜。研究CS质量浓度、ESP添加量、丙三醇（glycerol,Gly）添加量3 个因素对CS/ESP膜抗拉强度（tensile strength,TS）、断裂伸长率（elongation at break,EB）、水蒸气透过系数（water vapour permeability,WVP）和氧气透过率（oxygen permeability,OP）的影响。在此基础上采用主成分分析法对膜性能进行综合评价,并通过响应面法优化试验得到CS/ESP膜制备的最佳工艺参数,具体如下：CS质量浓度4.9 g/100 mL、Gly添加量49%（m/m）、ESP添加量1.9%（m/m）,对应CS/ESP膜的TS、EB、WVP和OP分别为4.97 MPa、109.12%、1.31×10－12 g/（cm·s·Pa）和1.19×10－5 cm3/（m2·d·Pa）。傅里叶变换红外光谱分析表明ESP和CS具有较好的相容性。X射线衍射和热重分析结果表明ESP的添加提高了CS/ESP膜的结晶度和热稳定性。扫描电子显微镜分析表明CS/ESP膜具有光滑的表面和断面形貌,没有明显的突起和腔。     

中国居民水产品中四种常见重金属暴露评估

目的评估中国居民水产品中铅、镉、汞、砷四种重金属的暴露水平和健康风险。方法利用2013—2017年水产品中铅、镉、汞、砷的含量监测数据和相应食物消费量数据,采用简单分布评估方法,计算中国居民水产品中四种重金属的摄入情况,依据相应健康指导值或基准剂量评估其潜在危险。结果各性别-年龄组人群镉、甲基汞的暴露量均低于其相应健康指导值,但除66岁以上女性组镉平均暴露量外,平均暴露量均在相应健康指导值的5%以上,高端暴露量(P95)超过健康指导值的20%。各人群铅、无机砷的暴露限值(MOE)均高于1。2～6岁性别-年龄组除无机砷外,另三种重金属平均暴露量和P95在各性别-年龄组中均最高。水产品中四种重金属贡献率最高的为海蟹和鱼类。结论中国居民通过水产品的铅、镉、汞、砷暴露量总体上低于相应的健康指导值或基准剂量,但达到通过制定限量标准进行管理的水平。鱼类和海蟹是对四种重金属暴露贡献率最高的水产品,高消费人群的重金属暴露需要加以关注,建议进一步开展重金属的累积暴露评估研究,明确水产品中重金属的累积暴露风险。     

Methods of choosing the optimal parameters for solid fuel combustion in stoker-fired boilers

Stoker-fired boilers are used for the combustion of coal and solid wastes. The most important disadvantage is their low thermal efficiency. The authors present methods of choosing the optimal rate of travel of the grid and height of the fuel layer basing on both realscale and laboratory measurements. Basing on industrial-scale experiments the authors calculated the optimal thermal efficiency and main energy losses using the least squares adjustment method. The stepwise regression method was used to correlate the main energy losses as functions of grid operating parameters. These correlations were used in the optimization method to estimate the optimal rate of travel of the grid and height of the fuel layer. The minimum retention time of the coal can be also calculated.     

Expression patterns of hepatic genes involved in lipid metabolism in cows with subclinical or clinical ketosis

Dairy cows with ketosis are characterized by high blood concentrations of ketone bodies and hepatic lipid metabolism disorder. The discrepancies in the abundance of mRNA encoding a variety of hepatic candidate genes in varying degrees of ketotic cows represent specific responses of the liver to the challenge of fatty acids and ketone bodies. Importantly, the expression disorder of hepatic genes involved in lipid metabolism plays a promoting role in the onset and progression of ketosis. Thus, the aim of this study was to investigate the expression patterns of genes involved in the hepatic fatty acids uptake, transport, activation, β-oxidation, synthesis, and esterification in the cows with subclinical ketosis (SCK) or clinical ketosis (CK). Twenty-four cows were selected into control [n = 8, β-hydroxybutyrate (BHB) ≤0.6 mM], SCK (n = 8, 3.0 > BHB ≥ 1.2 mM), and CK (n = 8, BHB ≥3.0 mM) groups according to the blood BHB concentration and clinical symptoms. The accumulation of hepatic lipid, as indicated by triglycerides (TG) contents and Oil Red O and hematoxylin and eosin staining, was pronouncedly exacerbated in the tCK group compared with the control and SCK groups. The hepatic mRNA expression of fatty acids transport and activation genes, liver fatty acid-binding protein (FABP1) and long-chain acyl-CoA synthetase 1 (ACSL1), were both significantly higher in the SCK and CK groups than in the control group. The expression levels of peroxisome proliferator-activated receptor α (PPARA) and its target genes, carnitine palmitoyltransferase 1A (CPT1A) and carnitine palmitoyltransferase 2 (CPT2), were significantly elevated in the SCK group but reduced in the CK group compared with control group. Furthermore, the gene expression level of sterol regulatory element-binding protein 1 (SREBP1) and the protein expression level of sterol regulatory element-binding protein 1c and its target genes acetyl-CoA carboxylase 1 (ACC1), fatty acid synthase (FAS), and stearoyl-CoA desaturase-1 (SCD1) and TG synthesis genes diacylglycerol acyltransferase 1 (DGAT1) and diacylglycerol acyltransferase 2 (DGAT2) were significantly higher in the CK group relative to the control group. In short, the present data indicated that hepatic fatty acids uptake, transport, and activation are significantly increased in cows with SCK and CK, hepatic fatty acids β-oxidation is significantly increased in SCK cows but markedly decreased in CK cows, and hepatic fatty acids and TG synthesis are significantly increased in CK cows, thereby inducing hepatic steatosis in CK cows.     

Impact of extended refrigerated storage and freezing/thawing storage combination on physicochemical and microstructural characteristics of raw whole and skimmed sheep milk

The impact of freezing (1 month + thawing at 7 or 25 °C) and extended refrigeration (4 days, 7 °C) on physicochemical and microstructural characteristics of raw whole and skimmed sheep milk were assessed. Refrigerated storage resulted in higher sedimentation and creaming (whole milk), possibly due to proteases and agglutinins. Freezing/thawing processes in whole milk increased the particle size and creaming when samples were thawed at 7 °C. Skimmed milk showed an increase in buffering capacity and a reduction in soluble calcium immediately after thawing at 25 °C, suggesting that although the changes in fat are the main alterations caused by slow freezing of sheep milk, minor changes in saline balance can occur. An evaluation of the results showed that frozen and thawed milk in domestic equipment (commonly found in smallholdings) alter the milk microstructure, and it is therefore preferable to use extended refrigeration to accumulate the milk before dairy production.     

低盐固态发酵法酱油生产企业内部循环经济发展模型构建的探索

文中重点介绍了低盐固态发酵法酱油生产企业建立内部循环经济发展模型的相关理论、构建原则、具体内容以及企业循环经济发展水平评价指标,结合低盐固态发酵法酱油清洁生产标准,全过程展现了从选择原料到成品出厂的物料循环、能源循环与水循环途径以及清洁生产相关技术的应用,为我国低盐固态发酵法酱油生产企业建立内部循环经济发展模型提供了可供借鉴的资料。     

Liver fibrosis is a common pathological change in the liver of dairy cows with fatty liver

Fatty liver (i.e., hepatic lipidosis) is a prevalent metabolic disorder in dairy cows during the transition period, characterized by excess hepatic accumulation of triglyceride (TG), tissue dysfunction, and cell death. Detailed pathological changes, particularly hepatic fibrosis, during fatty liver remain to be determined. Liver fibrosis occurs as a consequence of liver damage, resulting from the excessive accumulation of extracellular matrix, which distorts the architecture of the normal liver, compromising its normal synthetic and metabolic functions. Thus, we aimed to investigate liver fibrosis status and its potential causal factors including oxidative stress, hepatocyte apoptosis, and production of inflammatory cytokines in the liver of cows with fatty liver. Forty-five dairy cows (parity, 3–5) were selected, and liver biopsy and blood were collected on the second week postpartum (days in milk, 10–14 d). On the basis of the degree of lipid accumulation in liver, selected cows were categorized into normal (n = 25; TG <1% wet wt), mild fatty liver (n = 15; 1% ≤ TG <5% wet wt), and moderate fatty liver (n = 5; 5% ≤ TG <10% wet wt). Compared with normal cows, blood concentrations of nonesterified fatty acids and β-hydroxybutyrate, along with alanine aminotransferase and aspartate aminotransferase activities, were greater in the cows with fatty liver (mild and moderate). Hepatic extracellular matrix deposition, as indicated by Picrosirius red staining, was greater in cows with fatty liver than those with normal ones. In addition, we observed an increased proportion of collagen type I fiber in extracellular matrix with increased lipid accumulation in the liver. Compared with normal cows, the area of α-smooth muscle actin (α-SMA)-positive staining along with the mRNA abundance of collagen type I α 1 (COL1A1), ACTA2 (gene encoding α-SMA), and transforming growth factor-β (TGFB) were greater in cows with fatty liver. Compared with normal cows, hepatic contents of malondialdehyde, glutathione disulfide, and 8-isoprostane were greater, whereas total antioxidant capacity, the hepatic content of glutathione, and activities of antioxidant indicators, including superoxide dismutase, glutathione peroxidase, and catalase, were lower in cows with fatty liver. The number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cells and abundance of apoptosis-related molecules BAX, CASP3, CASP8, and CASP9 were greater in cows with fatty liver. However, mRNA abundance of the anti-apoptotic gene BCL2 did not differ. The mRNA abundance of pro-inflammatory cytokines including tumor necrosis factor-α (TNFA), interleukin-1β (IL1B), and interleukin-6 (IL6) was greater in the liver of cows with fatty liver. Overall, the present study indicated that fibrosis is a common pathological response to liver damage and is associated with oxidative stress, hepatocyte death, and inflammation.