制麦条件对大麦发芽过程中β-葡聚糖含量及β-葡聚糖酶变化的影响

本文对大麦发芽时,麦芽中β-葡聚糖酶的产生和β-葡聚糖降解的多种因素进行了试验分析。结果发现,在发芽时控制低温有利于β-葡聚糖酶的生成和β-葡聚糖酶的降解;浸麦水的pH在中性和偏酸性条件下有利于β-葡聚糖酶的产生,但是在pH中性和偏碱性条件下有利于β-葡聚糖的降解;镁离子,锌离子,钾离子和钠离子有助于β-葡聚糖酶的生成及β-葡聚糖的分解;铜离子会抑制β-葡聚糖酶活性及β-葡聚糖的降解。     

小麦组分含量与小麦芽β-葡聚糖酶活力的相关性分析

跟踪测定了小麦芽常规制麦过程中β-葡聚糖酶活力的变化,分析了不同阶段小麦芽β-葡聚糖酶活与原小麦β-葡聚糖含量、蛋白质含量、淀粉含量之间的相关性.结果表明:绿麦芽β-葡聚糖酶与原小麦β-葡聚糖含量呈负相关(P<0.10);干麦芽β-葡聚糖酶与原小麦β-葡聚糖含量呈显著负相关(P<0.05).绿麦芽、干麦芽β-葡聚糖酶均与原小麦蛋白质含量呈显著负相关(P<0.05).干燥过程中小麦芽β-葡聚糖酶活力增加与小麦水溶蛋白含量成负相关(P<0.10)、与小麦醇溶蛋白含量成显著正相关(P<0.05).     

酵母β-葡聚糖的研究进展及应用

β-葡聚糖是酵母细胞中存在的一种活性物质。酵母β-葡聚糖是由β-1,3键相连的D-葡萄糖组成的线性骨架及通过β-1,6键相连的分支结构构成。酵母β-葡聚糖有着对人体非常有益的生理功能,例如能提高免疫能力、显著地降血糖、降血脂等作用,在食品、医药、化妆品和水产养殖等行业中有巨大的商业价值。综述了酵母β-葡聚糖的结构与性质、β-葡聚糖的提取和检测方法、β-葡聚糖的生物活性及其应用,并展望了酵母β-葡聚糖的应用前景。     

大麦β-葡聚糖的凝胶特性及应用研究进展

大麦作为全球产量第四大谷物,并富含降低血浆胆固醇、控制血糖、免疫调节以及抗氧化等生理功能的大麦β-葡聚糖,具有广阔的开发前景。在食品体系中大麦β-葡聚糖可作为亲水胶体发挥作用,前人研究主要集中在添加大麦β-葡聚糖食品的加工工艺优化,和其作为功能性食品配料的应用,而大麦β-葡聚糖还可影响食品加工过程中组分间物理和化学反应,进而影响食品质构、营养和功能。因此文章介绍了大麦β-葡聚糖的分布、提取纯化和结构,以及β-葡聚糖精细微观结构与葡聚糖凝胶特性间的构效关系研究进展,发现β-葡聚糖的分子质量以及纤维三糖单元和纤维四糖单元的比例是影响β-葡聚糖的凝胶过程和凝胶微观结构的重要因素。还着重讨论了大麦β-葡聚糖在食品基质中形成凝胶影响食品物性的机制,为避免β-葡聚糖在食品中产生负面影响,扩展大麦β-葡聚糖在食品中的应用提供参考。     

来源与加工方式对β-葡聚糖理化特性的影响及其在肠道的降解机理

检索、归纳并分析近年来关于谷物和微生物中β-葡聚糖结构、功能特性及加工方式对其的影响,以及其在肠道中的降解机理和代谢途径的研究文献。综合显示,谷物中β-葡聚糖的分子质量及β-1,3/β-1,4的比例是决定其结构与性质的关键因素,微生物β-葡聚糖多为β-1,3和β-1,6糖苷键构成的支链多糖;加工方式可改变β-葡聚糖的分子质量、溶解性、黏度及功能特性;β-葡聚糖在生物体中,由肠道厌氧微生物酶系统逐步分解为短链脂肪酸,从而起到维持肠道菌群生态平衡、改善机体代谢及调节免疫的作用。该文综合论述了加工方式,对β-葡聚糖生物活性的影响机理对β-葡聚糖的开发提供参考。     

响应曲面法优化酵母β-葡聚糖酶解工艺及产物分析

采用β-葡聚糖酶对酵母β-葡聚糖进行酶解,利用单因素和响应面实验,以水溶性酵母β-葡聚糖得率为指标优化酶解工艺,并对水溶性酵母β-葡聚糖与原酵母β-葡聚糖的结构和热稳定性进行了研究。最佳酶解条件:底物质量浓度1.14 g/100 mL,酶活浓度0.16 U/mL,温度44℃,pH 4.2,水溶性酵母β-葡聚糖得率为39.89%。红外光谱分析结果表明,水溶性酵母β-葡聚糖与原酵母β-葡聚糖的糖苷键型均为β构型,分子构象相同。热稳定性分析表明,水溶性酵母β-葡聚糖和原酵母β-葡聚糖的特征分解温度分别为356℃和360℃,终止分解温度分别为740℃和780℃,热稳定性差异不大。     

燕麦β-葡聚糖的冻融法提取及其结构表征

目的:研究燕麦β-葡聚糖的冻融提取方法.方法:采用热水浸提-冻融循环提取燕麦β-葡聚糖,研究内源酶活性、水浸提温度和时间、燕麦β-葡聚糖质量分数和冻融次数等因素对β-葡聚糖得率和纯度的影响规律.采用气相色谱、红外光谱和核磁共振等手段对纯化的β-葡聚糖进行结构表征.结果:不灭内源酶活,55℃提取2h,将提取液浓缩至β-葡聚糖质量分数为1％,冻融3次,燕麦β-葡聚糖的得率为1.5％,纯度92％.通过仪器分析的方法证实冻融法提取到的物质是β-葡聚糖.结论:采用冻融法,不必添加任何化学试剂和酶,仅凭借冻融这一物理过程即可得到较高纯度的燕麦β-葡聚糖.     

大麦、麦芽、协定法麦芽萃取物及啤酒中β-葡聚糖含量的关系

通过选择低β-葡聚糖含量的大麦进行制麦试验,以直接了解降低β-葡聚糖所造成的问题。β-葡聚糖含量增加所带来的问题,迫切需要解决:即如何通过调整制麦工艺来减少β-葡聚糖的含量。大麦与成品酒中β-葡聚糖含量的关系至今并未十分清楚。此研究通过测定大麦、麦芽与协定法萃取物中β-葡聚糖的含量,从而确定它们之间的关系,并由此确定哪个可以更好的预测啤酒中β-葡聚糖的含量。大麦生长环境与基因型对这三者关系与预测啤酒中β-葡聚糖的含量也在本文中进行了研究。通过 Calcofluor-流动注射分析方法实现对60个大麦样品及其对应的麦芽、协定法细粉萃取物和啤酒中的β-葡聚糖含量进行了分析。结果显示麦芽协定法萃取物中β-葡聚糖的含量与用相应麦芽生产的啤酒中β-葡聚糖的含量有高度的相关性;大麦与啤酒中β-葡聚糖含量的相关性明显较低。此研究也证明了生长环境对大麦、麦芽、协定法萃取物和啤酒中β-葡聚糖含量的强烈影响;同时,基因组成对他们的影响也相当显著。     

酶法测定大麦提取物中β-葡聚糖含量的研究

在国际β-葡聚糖酶法测定β-葡聚糖含量的基础上,用纤维素酶代替昆布多糖水解酶水解β-葡聚糖,用β-葡聚糖酶代替β-葡萄糖苷酶,用苯酚-硫酸法代替葡萄糖试剂盒法测定β-葡聚糖酶解后得到葡萄糖含量,设计了适合我国应用的β-葡聚糖酶法测定方法。此法测定过程为：1．5mL浓度为60μg/mL的标准β-葡聚糖和一定浓度的样品,用浓度为50U/mL纤维素酶0．5mL酶解60min；然后用蒸馏水稀释至30mL,从中吸取0．5mL到另一试管,再加入浓度为2U/mLβ-葡聚糖酶1mL,作用15min后,用苯酚-硫酸法测定标准β-葡聚糖和样品酶解液中葡萄糖含量,计算出样品中β-葡聚糖的含量。     

燕麦β-葡聚糖-麦芽糊精体系流变学性质的研究

研究了燕麦β-葡聚糖-麦芽糊精体系的流变学特性.在不同剪切速率、温度、浓度条件下,时β-葡聚糖和麦芽糊精混合体系粘度的变化进行了初步探讨.结果表明,燕麦β-葡聚糖-麦芽糊精体系是剪切变稀型流体;1%的β-葡聚糖与麦芽糊精构成均一稳定体系,而2%的β-葡聚糖能和麦芽糊精溶液形成弱凝胶.     

Encapsulation of food ingredients

Microencapsulation is a relatively new technology that is used for protection, stabilization, and slow release of food ingredients. The encapsulating or wall materials used generally consist of starch, starch derivatives, proteins, gums, lipids, or any combination of them. Methods of encapsulation of food ingredients include spraydrying, freeze‐drying, fluidized bed‐coating, extrusion, cocrystallization, molecular inclusion, and coacervation. This paper reviews techniques for preparation of microencapsulated food ingredients and choices of coating material. Characterization of microcapsules, mechanisms of controlled release, and efficiency of protection/ stabilization of encapsulated food ingredients are also presented.     

Comparative metabolite profiling of raw milk from subclinical and clinical mastitis cows using 1H-NMR combined with chemometric analysis

The objectives of this study were to characterise and compare non-volatile metabolite profiles of raw milk from healthy, subclinical and clinical mastitis cows using a non-targeted proton nuclear magnetic resonance (¹H-NMR) metabolomic approach. A total of 46 metabolites were identified. Multivariate analysis allowed discrimination of milk from healthy and mastitis cows according to their ¹H-NMR metabolite profiles. Significant increases in acetate, formate, lactate, benzoate, hippurate, β-hydroxybutyrate, valerate, alanine, histidine, isoleucine, leucine, N-acetylamino acid, phenylalanine, threonine and valine content were associated with extremely high somatic cell count and clinical mastitis status of the cows. Furthermore, significant rises in hippurate, valerate, N-acetylglucosamine, histidine, isoleucine and leucine content could be used as potential biomarker for indicating subclinical mastitis infection of the udders. Beside the existing biomarkers for diagnosing mastitis in literatures, we found additional candidate metabolites, such as alanine, valerate and N-acetylglucosamine, in correlation with mastitis status of Thai crossbred Holstein dairy cows.     

Influence of laboratory homogenization procedures on trace element content of food samples: an ICP-MS study on soft and durum wheat

Sample contamination as a consequence of abrasion of grinding tools during the homogenization of food materials to be analysed for trace elements was addressed. The possible release of 15 trace elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se, Sn, V, Zn) from six different grinding and milling devices, operating either continuously or discontinuously, was evaluated. All the devices were commercially available and were representative of models usually employed in food and agricultural laboratories. Wheat grains belonging to one soft and one durum cultivar were used as test material. The determination of the analyte concentrations in subsamples submitted to the different preparation treatments was performed by quadrupole inductively coupled plasma mass spectrometry (Q-ICPMS). Accordingly, a suitable digestion method was developed and the ArC⁺ interference affecting Cr determination was evaluated and corrected. Statistical differences with respect to the control were detected for 10 elements (Al, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb) and in most cases contamination of the samples was traced back to the composition of the grinding equipment. None of the investigated devices was contamination-free with respect to all of the quantified elements. Abrasion of the grinding tools was higher with durum wheat than with soft wheat as a consequence of their different hardness.     

Antioxidant activities of extracts from selected culinary herbs and spices

Recently, interest in plant-derived food additives has grown, mainly because synthetic antioxidants suffer from several drawbacks. Furthermore, plant extracts have been shown to possess health-promoting properties. In the present study, hydrodistilled extracts from basil, laurel, parsley, juniper, aniseed, fennel, cumin, cardamom, and ginger were assessed for their total phenol content, and antioxidant (iron(III) reduction, inhibition of linoleic acid peroxidation, iron(II) chelation, 1,1-diphenyl-2-picrylhydrazyl radical-scavenging and inhibition of hydroxyl radical-mediated 2-deoxy-d-ribose degradation, site and nonsite-specific) activities. The extracts from basil and laurel possessed the highest antioxidant activities except for iron chelation. Although parsley showed the best performance in the iron chelation assay, it was less effective at retarding the oxidation of linoleic acid. In the linoleic acid peroxidation assay, 1 g of the basil and laurel extracts were as effective as 177 and 212 mg of trolox, respectively. Thus, both extracts are promising alternatives to synthetic substances as food ingredients with antioxidant activity.     

茶叶加工中品质关键组分的变化与调控机制

茶树起源于中国,茶叶是世界三大饮品之一.茶叶中富含茶多酚、蛋白质及氨基酸、生物碱、芳香族化合物、糖类、类脂化合物、维生素、无机物、叶绿素、酶等多种化合物.它们经过非发酵、微发酵、半发酵、全发酵及后发酵工艺,萎凋、杀青、揉捻、发酵、干燥等处理后,由于温度、压力、酶及微生物的作用,儿茶素在多酚氧化酶、过氧化物酶等的氧化聚合下分别形成茶黄素、茶红素、茶褐素等茶色素;β-D-糖苷类等香气前驱体在β-葡萄糖苷酶、β-樱草糖苷酶的作用下水解生成相应的醇类等香气物质;蛋白质水解成氨基酸,并形成不同的手性对映体,所以赋予茶叶特有的颜色、香气、滋味、外形以及其抑菌、抗病毒、抗氧化、防衰老、增强机体免疫、防癌抗癌、预防心脑血管疾病等功效,进而形成绿茶、白茶、黄茶、青茶、红茶、黑茶六大茶系.本文从茶叶成品色、香、味等关键组分入手,阐述其在加工过程中的变化规律和关键技术调控的相关性及存在问题,并探讨它们的形成机理,为提高茶叶品质提供理论依据.     

5—THE CONSTITUTION OF THE EPICUTICLE OF WOOL

Epicuticle, isolated from wool via the Allwörden reaction, was examined by electron microscopy and analysed chemically. It is proteinaceous; lipids and carbohydrates could not be detected. The component amino acids are: cystine, glycine, glutamic acid, serine, valine, alanine, lysine, α-amino-adipic acid, and threonine. A tentative model for the epicuticle is proposed.     

Psychrotrophs in dairy products: Their effects and their control

Health concerns and technological effects of psychrotrophic bacteria in dairy products are reviewed, as well as methods to control their presence and development. The various Gram‐negative and Gram‐positive psychrotrophic species are listed and, with respect to pathogenic psychrotrophs, emphasis is given on Listeria monocytogenes, Yersinia enterocolytica, and Bacillus cereus. The influence of psychrotrophic bacteria on the quality of raw milk, pasteurized and UHT milks, butter, ice cream, cheese, and powders is examined. Public health considerations of Listeria monocytogenes, Yersinia enterocolytica, and Bacillus cereus of these various dairy products are also presented. Methods that can be used to eliminate or control the development of psychrotropic bacteria include low or high temperatures, chemicals, gases, the lactoperoxidase system, lactic acid bacteria, microfiltration, bactofugation, lactoferrin‐related proteins, sanitation, flavors, and naturally occurring spore germinants.     

Ramie fibre: part I. Chemical composition and chemical properties. A critical review of recent developments

The monograph deals with a critical review of the recent research work and development on ramie, a long vegetable bast fibre. The review is divided into two parts. Part I discusses the progress of recent work on ramie, chemical components like fibre degumming, its effects on fibre composition, chemical constituents, i.e. hemicellulose, cellulose, non-cellulosic and mineral matters. Besides various chemical properties of native and modified fibres such as accessibility, infrared, cellulose I-V, DP, grafting, cross linking and resin finishing and dyeing etc. are dealt with.     

美人指等13个葡萄品种引种初报

本试验于1999年1月引进美人指、粉红亚都蜜、优无核、秦龙大穗、无核白鸡心、皇家秋天奇妙无核、红宝石无核、维多利亚、京玉、夏黑无核、高妻、红双味等13个葡萄品种，以巨峰为对照，定植在常德市澧县小渡口镇，观测了其生长特性、物候期及其果实产量与品质。结果表明：13个品种于避雨栽培条件下，适应常德市澧县的气候条件，定植后第二年美人指等品种平均株产超过7.5kg，品质较好，可在湖南适量发展。     

Sorbate and benzoate in Turkish retail foodstuffs

From 2008 to 2011, surveys were conducted to determine the levels of benzoic and sorbic acids and their respective salts in 983 retail food samples which included sauces, vegetable and fruit preparations, flavoured syrups, food supplements, cereals, bakery products, jelly, synthetic cream, sprays, mustards, jam and preserves, molasses, chewing gum, confectionery, non-alcoholic beverages, tea, wine, vinegar, brine and beers. The analysis involved methanol extraction of the foodstuff and direct determination by HPLC with UV detection. Quality assurance was employed with each batch of samples. Accuracy was ensured through regular participation in proficiency tests. Over this four-year period, a total of 23 samples (2.3%), some syrups, tomato sauces and fruit contained individual or combined levels of sorbic and benzoic acids above regulatory limits. Unauthorised use of benzoic acid was also detected in a syrup sample, bakery products and fruit preserves.