不同乳酸菌发酵的黄秋葵汁液在模拟体外消化过程中总多酚及抗氧化活性的变化

为筛选合适的发酵剂,研究不同乳酸菌发酵黄秋葵汁液中总多酚和抗氧化活性在体外模拟胃肠道环境下的变化规律。结果表明：经植物乳杆菌和鼠李糖乳杆菌发酵之后,黄秋葵汁液中游离的总多酚含量明显增加（P＜0.05）;发酵黄秋葵总多酚在模拟口腔消化后,其含量未发生显著变化（P＞0.05）;在胃消化过程中,黄秋葵总多酚释放量在消化30 min内显著升高,达到释放最高点（P＜0.05）,并在之后的胃消化过程中,释放量趋于稳定（P＞0.05）;在肠消化过程中,由于总多酚在此环境中易发生降解,含量显著降低（P＜0.05）。同时,由抗氧化能力的测定可知,黄秋葵消化液的抗氧化能力与总多酚含量呈正相关。植物乳杆菌发酵的黄秋葵样品消化终点总多酚含量相对较高,并具有较强的抗氧化活性。     

低温胁迫下烟苗多酚代谢及其抗氧化能力分析

为了明确在低温胁迫条件下烟苗中多酚物质代谢与抗氧化能力的关系,本研究以烟草K326为材料,对比分析了低温胁迫处理（4℃）和对照处理（25℃）烟苗叶片中多酚物质含量及其代谢酶活性和基因表达水平变化与植物抗氧化酶活性的关系。结果表明,低温胁迫处理后,烟草叶片萎蔫、细胞膜损伤严重,相对电导率升高;总酚含量受低温胁迫影响较小,木质素含量显著增加（p<0.05）;低温处理后,SOD活性显著升高（p<0.05）,CAT活性和总抗氧化能力（T-AOC）均低于对照;PAL、HCT和POD酶活性均升高,PAL、HCT和POD基因表达水平均上调。以上结果表明,低温胁迫促进烟苗多酚代谢中木质素合成,通过提高木质素含量增强细胞壁的保护作用是植物抵御环境胁迫的重要机制。     

植物多酚通过Nrf2/ARE信号通路抗氧化作用研究进展

植物多酚是植物体内重要的次生代谢产物,是重要的天然抗氧化剂,能够清除自由基和淬灭活性氧。Nrf2（NF-E2-related factor 2）/抗氧化反应元件（antioxidant response element,ARE）信号通路是增强机体抗氧化功能最重要的保护性信号途径,在细胞抵御氧化应激机制中有着重要的地位,是抗氧化研究领域的热点。本文综述了Nrf2/ARE信号通路的组成及其调节机制,总结植物多酚通过该信号通路增强机体抗氧化应激能力,减少细胞凋亡、参与神经保护、延缓衰老和减少氧化损伤等的能力,以期为植物多酚应用于抗氧化保健食品和药品的开发提供一定依据。     

使用水和水醇萃取酒花／颗粒酒花的多酚含量与抗氧化活性

本文研究的是酒花（（CVMagnum和Marynka）和颗粒酒花（T90型和T45型）使用水、50％甲醇、50％乙醇三种溶剂体系萃取后的多酚含量与抗氧化活性。使用水醇溶剂萃取酒花或颗粒酒花后的总多酚（TPC）和总黄酮类（TFC）含量与抗氧化活性（ABTS清除率）明显高于水溶剂萃取，并对绿原酸的获取更有利。使用水溶剂萃取酒花和颗粒酒花在总多酚（TPC）和总黄酮类（TFC）含量上没有明显差别；而使用水一乙醇萃取T45型相对T90型颗粒酒花的总黄酮类（TFC）含量明显提高。使用水溶剂萃取vMagnum型酒花和颗粒酒花相对CVMarynka型酒花有更高的总多酚（TPC）含量。不论乙醇类型或是酒花的产地不同，使用水醇萃取后在抗氧化活性方面没有明显差别。     

石榴花游离型和结合型多酚提取物抗氧化活性探究

提取石榴花中游离型和结合型多酚粗提物,探究两种多酚提取物的抗氧化能力。采用Folin-Ciocalteu法测定粗提物总酚含量,利用5种体外抗氧化法测定其抗氧化活性。结果显示:游离型多酚粗提物多酚含量显著高于结合型多酚粗提物（P<0.05）;吸收过氧自由基能力（oxygen radical absorbance capacity,ORAC）和清除过氧自由基能力（peroxyl radical scavenging capacity,PSC）测定中,两种多酚粗提物具有与水溶性维E相似的明显荧光动力学特征与剂量依赖趋势,游离型多酚粗提物抗氧化能力强于结合型多酚粗提物（P<0.05）,水溶性维生素E抗氧化能力显著强于两种多酚粗提物（P<0.05）;游离型多酚粗提物DPPH自由基清除能力（DPPH radical scavenging activity,DRSA）、总氧自由基清除能力（trolox equivalent antioxidant capacity,TEAC）和还原力能力（reducing power,RP）均强于结合型多酚粗提物（P<0.05）,但两种多酚粗提物的抗氧化能力均低于阳性对照维生素C（P<0.05）。研究表明:石榴花游离型和结合型多酚粗提物均具有一定抗氧化活性,且游离型抗氧化能力优于结合型,此研究可为天然抗氧化剂的开发和利用提供一定理论依据。     

桉叶多酚提取物体内外抗氧化活性评价

桉叶资源丰富且生物活性高,但少有研究对桉叶多酚提取物进行系统的抗氧化活性评价。本实验旨在研究纯化后桉叶多酚提取物体内外抗氧化活性。以化学法、RAW264.7巨噬细胞模型、秀丽隐杆线虫（以下简称线虫）模型为评价方法,以自由基清除率、抗氧化酶活力及线虫寿命等为指标,评价桉叶多酚提取物的抗氧化能力。结果表明,桉叶多酚提取物具有良好的自由基清除能力和还原能力,在一定质量浓度下效果接近抗坏血酸。桉叶多酚提取物能显著提高氧化损伤RAW264.7巨噬细胞内抗氧化酶（超氧化物歧化酶、过氧化氢酶）活力和谷胱甘肽含量,并显著降低丙二醛含量（P＜0.05）,呈量效关系。此外,桉叶多酚提取物显著降低常规培养和氧化损伤条件下线虫体内活性氧积累量（P＜0.05）,提高线虫抗氧化能力,起到延长线虫寿命的作用。桉叶多酚提取物在体内外均表现出良好的抗氧化活性,具备开发食品抗氧化剂或功能食品的潜力。     

不同益生菌发酵剂对复合果蔬汁品质的影响

以沙棘、胡萝卜和黑枣为原料制备复合果蔬汁,分别接种植物乳杆菌、鼠李糖乳杆菌及其组合（1∶1,体积比）进行发酵,比较复合果蔬汁发酵过程中乳酸菌总数、pH值、总酸、可溶性蛋白、还原糖、有机酸、总黄酮、总多酚和体外抗氧化活性等指标的变化。结果表明,植物乳杆菌、鼠李糖乳杆菌及其组合发酵复合果蔬汁中还原糖含量无显著差异。相比直接接种植物乳杆菌或鼠李糖乳杆菌单一菌种发酵复合果蔬汁,植物乳杆菌和鼠李糖乳杆菌耦合发酵可显著增加乳酸菌的菌落总数（P<0.05）,提高总酸、总黄酮、总多酚、乙酸和乳酸等物质的含量（P<0.05）,增加体外抗氧化活性（P<0.05）。     

10种广东药食两用植物的抗氧化和抗增殖活性评价

测定了10种广东药食两用植物的总黄酮含量（AlCl₃-NaNO₂法）和总多酚含量（Folin-Ciocalteu法）,评价了其抗氧化活性（DPPH自由基清除活性和羟自由基清除活性）和抗小鼠结肠癌MC-38细胞增殖活性（CCK-8试剂盒法）,分析了活性物质功效与其含量之间的相关性。结果表明:在10种广东药食两用植物中,总黄酮含量最高的为高良姜（85.76 ± 3.25 μmol CE/g DW）,含量最低的为沙姜（0.80 ± 0.05 μmol CE/g DW）和龙眼肉（0.69 ± 0.03 μmol CE/g DW）。总多酚含量最高的为高良姜（226.26 ± 9.17 μmol GAE/g DW）,含量最低的为沙姜（7.52 ± 0.67 μmol GAE/g DW）。清除DPPH自由基活性最强的为高良姜,活性最弱的为沙姜。清除羟自由基活性最强的为沙姜、益智仁和肉豆蔻（三者无显著性差异）,活性最弱的为陈皮。抗MC-38细胞增殖活性最强的为陈皮和高良姜,活性最弱的为龙眼肉。DPPH自由基清除活性与其总黄酮和总多酚含量之间均有显著正相关性（P<0.05）;抗MC-38细胞增殖活性与其总黄酮和总多酚含量之间均有极显著正相关性（P<0.01）;羟自由基清除活性与其总黄酮和总多酚含量之间相关性均不显著。药食两用植物的活性功效虽有剂量效应,但还受到其成分种类、协同作用等影响。     

巴西啤酒在自然老化和强制老化过程中多酚及抗氧化特性的变化研究

生产啤酒的主要原料为大麦,但在酿造过程中往往加入如玉米、大米和小麦等其它谷物。啤酒中含有具抗氧化特性的酚类物质,主要来自麦芽及酒花。啤酒又是一种不稳定的产品,在其储藏过程中会发生一系列物理、化学及风味物质的转化反应。本研究对两种巴西啤酒在自然老化（室温,4个月）及强制老化（42℃,6天）过程中的氧化特性进行了研究。主要检测了以下指标：总多酚含量、DPPH值（自由基清除能力）、还原力及铜离子还原活力等。结果表明,在啤酒的强制老化过程中总多酚含量以及抗氧化活力并没有明显改变,自然老化过程中多酚含量和抗氧化活力有所降低。     

不同品种猕猴桃汁抗氧化成分及体外抗氧化活性比较

本文以陕西省和四川省两大主产区的美味、中华和软枣3大种系12个品种猕猴桃为材料，测定其果汁中主要抗氧化活性物质多酚、类黄酮、V_C和果实中单体酚含量，比较其体外抗氧化活性，并将抗氧化活性物质和果汁抗氧化能力进行相关性分析，筛选抗氧化物质含量高、抗氧化活性强的品种。结果表明，不同品种猕猴桃的抗氧化活性物质含量和抗氧化能力有显著性差异（P<0.05），V_C在不同品种间的含量差异较大，范围在27.300~130.380 mg/100 g之间；软枣系两品种（益玉和绿迷）类黄酮含量显著高于其他品种（P<0.05）；原儿茶酸、儿茶素、绿原酸、表儿茶素为猕猴桃中主要的多酚类化合物；红阳、翠香、亚特、华优对DPPH·和ABTS+·的清除能力较强，益玉和绿迷对·OH的清除能力和总还原力较强；各品种猕猴桃多酚含量与总还原力具有显著相关性（P<0.05），单酚含量之间、单酚与抗氧化活性之间也有相关性。根据抗氧化活性进行聚类分析，可将12个品种猕猴桃分为6类。综合分析，12个品种中以软枣猕猴桃的抗氧化活性最强。研究结果为猕猴桃鲜食及加工过程中高抗氧化活性品种的选择提供了科学依据。     

INDICATOR AND PATHOGENIC BACTERIA IN GUACAMOLE AND THEIR BEHAVIOR IN AVOCADO PULP

The presence of some indicator microorganisms and pathogenic bacteria in guacamole sampled from restaurants and street vendors, and the behavior of Salmonella spp. , Staphylococcus aureus, and Escherichia coli O157:H7 were studied in avocado pulp. Coliform, yeast and mold populations showed a wide dispersion, in agreement with the diversity of sanitary conditions observed among places sampled. The frequency of Salmonella spp. , Listeria monocytogenes, and E. coli were 1.3, 16.0, and 60.0 %, respectively; with higher numbers among street vendors. Populations of E. coli ranged from 29 to 3800 NMP/g and S. aureus from 2.95 to 5.35 log CFU/g. Thirteen out of 16 hemolytic L. monocytogenes strains were pathogenic for mice. In avocado pulp Salmonella spp. and E. coli O157:H7 showed a lag phase close to 3 h, and a generation time of 54 min and 1.23 h, respectively. No growth of pathogens was observed in avocado pulp stored at 4-7C.     

CHANGES IN THIOL AND DISULPHIDE CONTENTS IN BARLEY EMBRYOS DURING DORMANCY AND AFTER-RIPENING

During after-ripening, moistened embryos of Balder barley were initially unable to release glutathione and cysteine from peptides and alcohol-soluble proteins already present in the embryo; later they were able to do so. When dormancy was broken by soaking the grains in gibberellic acid, the embryos rapidly released glutathione and cysteine, immediately after harvest-ripeness. A good correlation was found to exist between the sum of the amounts of glutathione and cysteine found in the embryos after 24 hr. soaking and the percentage of grains germinated in three days.     

TRENDS IN SUPPLY AND DEMAND FOR MILK AND DAIRY PRODUCTS IN THE UK

The paper examines the changes in yields and dairy cow numbers in recent years and considers the likely economic prospects for investment in modern dairy units. With full Community prices applied in the UK at a realistic rate of exchange, dairying would be very profitable. In spite of the setback between 1973 and 1975 the milk output objective of the Government's White Paper 'Food from Our Own Resources' should be reached in the first half of the 1980s. Liquid milk consumption will be fairly stable in the future, but with the higher prices under the Community régime the butter market will contract. A modest increase in cheese consumption will continue. Higher milk production in the UK and a reduced market will increase self-sufficiency. In spite of the European surplus in the dairy sector the competitive strength of the UK industry at Community prices is substantial and it is economically right for it to expand.     

AFLATOXIGENIC ASPERGILLI IN FOODS AND FEEDS IN UGANDA

Studies conducted during the sixties and the seventies on food crops in Uganda showed that the populace was exposed to consumption of aflatoxin-contaminated foods. These studies also linked the highest incidence of liver cancer in the world to the presence of high levels of aflatoxins in the food and beverages. After a lapse of a decade, it was of interest to investigate the occurrence of aflatoxins and aflatoxigenic fungi in staple Ugandan food crops and poultry feeds derived from these foodstuffs. A simple, rapid and reproducible procedure was used. The procedure consisted of growing or culturing feed grains on a selective medium, Aspergillus flavus/parasiticus agar (AFPA) followed by screening for aflatoxin producing fungi on a coconut agar medium (CAM) under UV light with a subsequent confirmatory screening method for aflatoxin production by the fungi in pure culture. Fifty-four samples consisting of corn and peanuts, soybean and poultry feed were analyzed for content of aflatoxigenic. A. flavus/parasiticus and 25 of the samples were also screened for aflatoxins B₁ and G₁, zearalenone, sterigmatocystin, ochratoxin A, citrinin, vomitoxin, and diacetoxyscirpenol (DAS). Aflatoxigenic A. flavus/parasiticus was detected from the majority of corn (77%), peanuts (36% human food and 83.3% animal feed) and poultry feed (66.6%). but not from soybean samples. Two samples out of 25 contained detectable levels of aJatosin B, (20 ppb). For the jirst time other mycotoxins, zearalenone (3 samples) and vomitoxin (2 samples) were detected in corn from Uganda.     

NITRATE AND NITRITE CONTAMINATION IN VEGETABLES IN CHINA

This paper reviews recent studies of nitrate and nitrite contamination in Chinese vegetables. Nitrate and nitrite contamination is very serious and increases the amount of nitrogenous fertilizer applications. Factors influencing nitrate and nitrite contamination in vegetables are analyzed and discussed.