Mass spectrometric detection of marker peptides in tryptic digests of gelatin: A new method to differentiate between bovine and porcine gelatin

Gelatin is a mixture of polypeptides obtained by hydrolysis of collagen primarily from bovine and porcine skin and bones. The similarity between different gelatins makes it difficult to trace their species origin. In this work, a new method for differentiation between bovine and porcine gelatin was developed based on detection and identification of marker peptides in digested gelatins. Sequence alignment analysis indicates that bovine and porcine Type I collagen contain differential sequences. The gelatins were digested by trypsin, and the resulting peptides were analyzed by high performance liquid chromatography/tandem mass spectrometry (HPLC–MS/MS). The marker peptides specific for bovine and porcine were successfully detected in the digested bovine and porcine gelatin, respectively. Comparative analysis indicated that more marker peptides could be detected in gelatin with a higher mean molecular weight. It was found that proline hydroxylation was a key factor affecting the peptide identification. For peptides such as GPPGSAGSPGK and GPPGSAGAPGK detected in digested bovine and porcine gelatin, respectively, the sequence should be verified manually since the mass shift caused by proline hydroxylation can be confused with the mass difference between Ser and Ala residues. The results indicate that detection of marker peptides in the digested gelatin sample using HPLC–MS/MS is an effective method to differentiate between bovine and porcine gelatin.     

健康人体及保健品中乳酸菌和双歧杆菌的抗药性分析

目的:研究常用抗生素对来自健康人体和保健品的乳酸菌的影响.为构建乳酸菌和双歧杆菌食品级基因克隆和表达系统,为研制益生菌食品级微生态制剂而筛选无耐药性受体菌株和安全菌株.为乳酸菌的抗性筛选提供科学依据.方法:采用标准药敏纸片琼脂扩散法(K-B法),以金黄色葡萄球菌ATCC 25923为标准对照菌株,研究15株乳酸球菌,14株乳酸杆菌,5株双歧杆菌对8大类19种常用抗生素的敏感性.结果:15株乳酸球菌对氨苄西林、青霉素G、头孢霉素、头孢曲松、卡那霉素、四环素、红霉素、氯霉素均敏感或中度敏感:对磺胺、多黏菌素B均耐药;对其它抗生素表现出不同药敏性.14株乳杆菌都对氨苄西林、青霉素G、头孢霉素、卡那霉素、红霉素、四环素、氯霉素敏感或中度敏感;对磺胺、甲氧嘧啶、多黏菌素B均耐药:对其它表现出不同药敏性.5株双歧杆菌均对氨苄西林、青霉素G、头孢霉素、卡那霉素、甲氧苄氨嘧啶、红霉素、四环素、氯霉素敏感或中度敏感;对庆大霉素、阿米卡星、链霉素、磺胺、杆菌肽、环丙沙星均耐药;对其它抗生素表现出不同药敏性.     

外在因素对芦荟多糖提取率的影响

研究结果表明,芦荟品种、干燥方法及冷藏过程对芦荟多糖提取率有一定的影响,适合芦荟多糖提取的芦荟品种是库拉索芦荟;采用冻干技术,能提高芦荟多糖的提取率;随着芦荟鲜叶冷藏时间的延长,芦荟多糖的提取率明显降低。     

超声对酵母细胞膜通透性的影响

用不同参数的变幅杆浸入式超声波作用酵母细胞,测定细胞内核酸、蛋白质及FDP(1,6-二磷酸果糖)3种物质渗出率,再用透射电镜观察细胞形态。探讨超声场对酵母细胞膜通透性影响的最佳参数及机理。结果表示,超声场的最佳参数是:电功率500W、脉冲时间3s、间隙时间4s、脉冲总时间共225s,影响酵母细胞膜通透性变化的主要机制是空化作用使细胞膜在一定程度上损伤产生穿孔效应,细胞膜的通透性提高。     

萝卜汁与苹果汁复合饮料的研制

研究采用萝卜与苹果为原料，利用酶水解提高出汁率，结合热澄清与明胶沉淀优化澄清的效果，并通过止交试验确定参数，制成果蔬复合汁。结果表明：以萝卜汁：苹果汁=1：2，加糖量为10％，柠檬酸为0．01％，稳定剂为0．1％海藻酸钠 0．1％黄原胶，制成的萝卜苹果复合汁营养丰富，口感独特。     

烤烟新品种中烟90选育及其特征特性

烤烟新品种中烟90是根据基因重组和累加效应原理,通过 G-28、单育2号和净叶黄三亲本复合杂交,经加代繁殖和混合选择,于1990年育成。1991年通过省级品种审定。1992年通过全国烟草品种审定。其原烟多桔黄或金黄色,光泽较强,结构疏松,厚度适中。还原糖19.30%,尼古丁2.24%,总氮1.85%,钾(K_2O)2.48%,糖碱比8.62,氮碱比0.82,主要化学成分适宜,比例较协调。卷烟评吸香气质较好,香气量较多,劲头适中,燃烧性好。烟叶外观质量与 G-28和NC89相近,内在品质优于 NC89。与 G-28相当。经六年多点试验、全国区试和生产示范,中烟90平均亩产176.3kg,均价2.89元,上等烟25.22%,亩产值513.72元。分别比对照品种增产17.64—27.81%,均价提高0.28—1.14元,上等烟增加2.67—8.28个百分点,亩增收102.84—165.92元,提高30.86—38.28%。高抗黑胫病,抗气候斑点病,耐赤星病和花叶病。主要农艺性状遗传相对稳定。具有优质、稳产、多抗(耐)、适应性广、抗逆力较强、耐肥和易烘烤等特点。     

国产混合型卷烟与国外知名品牌混合型卷烟的分析比较及发展思路

选择市场销售份额较大、档次较高的国产混合型卷烟与国外知名品牌的混合型卷烟进行系统详细的分析比较,找出我国混合型卷烟在物理特性、烟支结构、化学成分、烟气特征、感官质量等各个方面与世界知名品牌的差距。我国混合型卷烟在设计思路及化学成分上存在以下不足：（１）卷烟吸阻分布不合理,滤嘴吸阻偏低;（２）卷烟纸透气度偏高,而滤嘴通风稀释较少;（３）卷烟烟丝化学成分不协调,糖氮比偏高、氮碱比偏低、糖碱比则有高有低。这些差异是造成国产混合型卷烟吸味不佳及焦油量偏高的主要原因。针对这些不足,文章指出了我国混合型卷烟的发展思路及研究方向,认为应从产品设计、工艺加工、基础研究等方面入手。     

食用油脂物理精炼和化学精炼诸多因素的比较

目前,在我国具有一定规模的禽用油脂精炼工厂（车间）中,以物理精炼或化学精炼的方法加工着不同品种的植物油脂,或以此两种不同的方法加工着同一品种的油脂。这两种方法的优缺点已成为多年来争议的焦点之一。列举了物理精炼和化学精炼中的许多因素,并加以对照、比较,以期对它们有更好的了解。     

蓖麻籽油加工生产技术

介绍了蓖麻籽的预处理、压榨及浸出生产的技术和工艺参数,同时介绍了蓖麻籽油的精炼技术及参数。蓖麻籽油由于其具有与其他植物油性质不同的特点,因此在加工生产过程中也具有某些特点     

Polycyclic aromatic hydrocarbons in riverine runoff of the Pearl River Delta (China): concentrations, fluxes, and fate

On the basis of a monthly sampling effort from March 2005 to February 2006, the total concentrations of the sums of 27 and 15 polycyclic aromatic hydrocarbons (defined as sigma27PAHs and sigma15PAHs, respectively) in riverine runoff of the Pearl River Delta (PRD), China, and associated fluxes were determined. No clear temporal and spatial trends of PAH concentrations were found at all eight riverine runoff outlets where the samples were collected. The annual fluxes of sigma27PAHs and sigma15PAHs from the PRD to the coastal ocean were 60.2 and 33.9 metric tons, respectively. Assuming that riverine flux was positively related to the regional emission of PAHs, the annual riverine fluxes from five major rivers in China to the global oceans were estimated, which are quite significant relative to other major rivers of the world. On the basis of mass balance considerations, approximately 87% of sigma15PAHs inputting to the Pearl River Estuary and northern South China Sea was derived from riverine runoff from the PRD. In addition, approcimately 22.3 metric tons of sigma15PAHs annually outflow to open seas, which is equivalent to a concentration of 0.34 pg/L in the global oceans if the PAHs are evenly distributed in the upper 200 m of the water column. A comparison with the global background level of PAHs indicated that approximately 0.4% of PAHs in the open oceans may have been contributed by 1-year discharge from the PRD.