提取条件对裸燕麦β-葡聚糖分子量分布的影响

为给裸燕麦β-葡聚糖的开发应用提供科学依据,以山西产裸燕麦为原料,研究了溶剂、温度、提取时间和β-葡聚糖酶水解等提取条件对燕麦β-葡聚糖分子量分布的影响.结果表明,较强的酸性和碱性条件会导致燕麦β-葡聚糖分子量下降,水提取β-葡聚糖的分子量较高.β-葡聚糖的分子量随着提取温度的提高而增加,随着提取时间的延长而下降.不同条件下提取的燕麦β-葡聚糖分子量分布在340～2 000 kD之间.β-葡聚糖酶水解会使β-葡聚糖分子变小,在几乎完全水解时分子量为2～5 kD.     

燕麦籽粒β-葡聚糖的积累动态

为给燕麦优化栽培技术措施的制定和高β-葡聚糖含量的品种选育提供理论依据,以不同地区的四个燕麦品种为试验材料,对燕麦籽粒β-葡聚糖含量的变化规律进行了研究。结果表明,从开花到籽粒完全成熟,哥葡聚糖含量呈逐渐增长的趋势。其中总β-葡聚糖在花后15d内迅速合成,是β-葡聚糖合成积累的关键时期,之后合成和积累速度减缓,其中可溶性β-葡聚糖在花后10d内积累速度较快,而后变缓。不同燕麦品种的β-葡聚糖含量存在显著差异,而且可溶性β-葡聚糖所占比例表现为皮燕麦高于裸燕麦。从燕麦籽粒形成到成熟,不同品种籽粒中葡萄糖含量均呈先上升后下降的趋势,且花后15d左右达到最大值,葡萄糖含量与β-葡聚糖含量没有显著相关性,葡萄糖含量不是燕麦籽粒中β-葡聚糖合成的限制因素。     

大麦穗废弃物中提取β-葡聚糖的初步研究

以大麦穗废弃物为原料,通过碱液浸提、胰酶水解和乙醇、硫酸铵、异丙醇的先后沉淀,提取纯化β-葡聚糖。分别以自制β-葡聚糖和进口β-葡聚糖为底物,用β-葡聚糖酶活测定比较法,得出自制β-葡聚糖纯度为77.12%。淀粉碘液显色反应结果表明淀粉含量少,还原糖仅为0.83%,自制糖中蛋白质含量平均占5.91%,β-葡聚糖提取率平均为1.08%,最高达1.44%。     

燕麦籽粒β-葡聚糖的积累动态

为给燕麦优化栽培技术措施的制定和高β-葡聚糖含量的品种选育提供理论依据,以不同地区的四个燕麦品种为试验材料,对燕麦籽粒β-葡聚糖含量的变化规律进行了研究.结果表明,从开花到籽粒完全成熟,β-葡聚糖含量呈逐渐增长的趋势.其中总β-葡聚糖在花后15 d内迅速合成,是β-葡聚糖合成积累的关键时期,之后合成和积累速度减缓,其中可溶性β-葡聚糖在花后10 d内积累速度较快,而后变缓.不同燕麦品种的β-葡聚糖含量存在显著差异,而且可溶性β-葡聚糖所占比例表现为皮燕麦高于裸燕麦.从燕麦籽粒形成到成熟,不同品种籽粒中葡萄糖含量均呈先上升后下降的趋势,且花后15 d左右达到最大值,葡萄糖含量与β-葡聚糖含量没有显著相关性,葡萄糖含量不是燕麦籽粒中β-葡聚糖合成的限制因素.     

燕麦β-葡聚糖的合成与积累

燕麦β-葡聚糖具有明显的保健功效,这方面的研究已引起国内外越来越多科学家的关注。燕麦β-葡聚糖具有β-（1,3）（1,4）两种糖苷键,而且排列有序,主要分布于籽粒糊粉层,通常与其它物质结合存在。燕麦β-葡聚糖是在高尔基体中合成的,但β-葡聚糖的合成过程目前还不清楚,β-葡聚糖合成酶（或复合体）可能是合成过程的关键酶。除遗传因素外,水分供应、总辐射、矿质营养、籽粒成熟期温度等环境因素均对β-葡聚糖含量有显著影响。     

燕麦β-葡聚糖的保健作用及影响其积累的因素

燕麦因具有较高的营养价值和保健价值,已引起国内外专家和广大消费者的关注。大量研究表明,燕麦β-葡聚糖能预防和治疗由高血脂引起的心脑血管疾病,具有明显的降低血脂和血清胆固醇的作用。关于燕麦β-葡聚糖在人体内的作用机理,目前虽已有一些假说,但均未取得充分的证据。燕麦β-葡聚糖的含量存在遗传差异,裸燕麦的含量通常高于皮燕麦,不同基因型的裸燕麦,其β-葡聚糖的含量也存在显著差异。环境因素对燕麦β-葡聚糖含量也有明显影响,氮素供应的增加通常会提高β-葡聚糖含量,但是其他环境因子包括磷、钾等矿质元素对燕麦籽粒β-葡聚糖合成及积累的影响还不清楚。     

青稞β 葡聚糖含量的基因型差异及优质种质的筛选

为了给青稞品质育种提供参考,采用国际通用的混合键β-葡聚糖分析方法测定了195份青稞种质的(1→3),(1→4)-β-葡聚糖含量,结果显示,测定材料的平均β-葡聚糖含量为5.10％,变化范围为3.03％～7.16％;有21份材料的含量高于6％,1 5份材料低于4％,可分别用于食用、饲用和酿造用品种的育种.青海省18个育成品种(系)的β-葡聚糖含量变化范围为3.68％～6.48％,昆仑2号和昆仑10号β-葡聚糖含量分别高达6.23％和6.49％,05-鉴12和09-鉴16的β-葡聚糖含量最低,分别为3.77％和3.68％.不同棱形、粒色和粒重的种质之间β-葡聚糖含量无显著差异.     

燕麦β-葡聚糖降血糖性能研究进展

本文从三个方面综述了燕麦β-葡聚糖降血糖性能研究进展。首先从食品血糖生成指数(glycemic index,GI)、餐后血糖、空腹血糖和α-淀粉酶活性等方面阐述了燕麦β-葡聚糖降血糖的功效,进而介绍了燕麦β-葡聚糖的结构因素——分子量和含量,以及食品加工过程对其降血糖功效的影响,最后综述了燕麦β-葡聚糖几种可能的降血糖机制,以期对后续研究提供参考。     

茶树不同组织结构中纤维素酶的活性差异研究

纤维素酶是重要的水解酶,对植物的生长发育及新陈代谢发挥着重要作用。为了解茶树中纤维素酶的活性变化特征,以茶树品种‘凫早2号’为研究对象,测定其不同组织结构中纤维素酶3种主要组分内切葡聚糖酶、外切葡聚糖酶和β-葡萄糖苷酶的活性。结果显示,内切葡聚糖酶在茶树一芽四叶中随着叶片成熟度增加,酶活性增加,表现为:第四叶第三叶第二叶第一叶芽,与β-葡萄糖苷酶活性呈现相反趋势;外切葡聚糖酶和β-葡萄糖苷酶都是在第四叶活性最低。内切葡聚糖酶在茶树花朵中活性最高,而外切葡聚糖酶和β-葡萄糖苷酶分别在叶片、果皮中活性最高。胞质蛋白中内切葡聚糖酶和β-葡萄糖苷酶活性显著高于膜蛋白中的酶活性,但胞质蛋白、膜蛋白中都未检测到外切葡聚糖酶活性。     

大麦β—葡聚糖酶的研究和展望

主要存在于大麦糊粉层和质片中的大麦β-葡聚糖酶（1，3－1，4－β－葡聚糖酶）属于诱导酶，种子萌发期间受赤霉酸（GA）诱导而激活。1，3－1，4－β－葡聚糖酶和1，3－β－葡聚糖酶基因是β－葡聚糖酶基因家族中两类，这两类β－葡聚糖酶水解酶具有不同的特性和功能。它们与大麦的制啤和抗病密切相关，遗传工程将为大麦的品质改良和选育抗病品种提供新的机遇。     

Role of oxidative cleavage and acid hydrolysis of oat beta-glucan in modelled beverage conditions

The effects of organic acids (ascorbic, citric and malic acids) associated with beverages were studied in an unpurified oat beta-glucan extract with the purpose of examining the stability of cereal beta-glucan in beverage conditions. Addition of ascorbic acid caused an immediate decrease in viscosity of the extract and the MW of beta-glucan. Citric and malic acid affected moderately and only after a heat treatement. This indicated a dominating role of ascorbic acid induced oxidative cleavage compared to the generally proposed acid hydrolysis of beta-glucan. The nature of ascorbic acid induced cleavage was studied with inhibitors (glucose, mannitol, catalase and phytic acid) and catalysts (Cu- and Fe-ions) of hydroxyl radical attacks. Glucose, mannitol and catalase inhibited and the metals effectively catalysed the viscosity decrease. These indicated that the degradation of beta-glucan in the ascorbic acid treated extract was induced by metal-catalysed hydroxyl radicals. Also, the beta-glucan extract used as a matrix lost its viscosity during storage (+6 °C) concurrently with MW decrease of beta-glucan. When added to the extract, mannitol, glucose and catalase each showed a slight stabilising trend and Fe²⁺-ions caused an immediate decrease in viscosity. The oxidative cleavage appeared to be an important factor to consider in developing novel aqueous beta-glucan enriched products.     

Effect of size reduction by freeze-milling on processing properties of beta-glucan oat bran

An effect of freeze-milling on processing properties of beta-glucan oat bran has been evaluated. A comparison with existing, patented methods of high molecular weight oat beta-glucan has been carried out. The new method employs raw material pre-treatment with freezing and milling in a hammer mill, resulting in significant reduction of particle size – 89% was between 80 and 50 μm in comparison with initial material when 79% were between 250 and 200 μm. Reduction of particle size also improved some process parameters of extraction technology – 30% improvement in fat removal during first stage of beta-glucan recovery was observed. The achieved pilot plant yield of product containing beta-glucan extraction was 64,03%, purity (ie. beta-glucan content), of achieved product was 84,4% and average molecular weight was about 69,500 g/mol.     

Isolation of beta-(1-3) glucan compound from the water extract of indonesian jamur tanduk (Termitomyces eurirrhizus Berk)

Jamur Tanduk (Termitomyces eurirrhizus Berk) is one of uncultivated edible mushrooms from genus Termitomyces found in various regions in Indonesia. The purpose of this study is to analyze the chemical structure of its beta-glucan compound that possesses bioactivity as lowering cholesterol levels. Isolation and identification of beta-glucan compound from water extract of Jamur tanduk (local name), Termitomyces eurirrhizus Berk collected in Sumedang has been done. beta-glucan was isolated with Wasterlund methods and obtained as white powder. Isolated compound was identified based on interpretation of spectroscopies data such as Ultra-Violet (UV), Infra-Red (IR) and nuclear magnetic resonance one dimensional such as 1Hidrogen-Nuclear Magnetic Resonance (1H-NMR), 13Carbon- 13C-NMR) and Distortionless Enhancement by Polarization Transfer (DEPT) and two dimensional such as Correlation spectroscopy (COSY), Hetero Multiple Quantum Connectivity (HMQC) and Hetero Multiple Bond Connectivity (HMBC). The determination of molecule weight of sample based on viscosity measurements and obtained that beta-glucan has 322 molecules of glucose.     

The effects of extrusion on the content and properties of dietary fibre components in various barley cultivars

Wholemeal flour from five Czech spring barley materials was processed in a single-screw extruder at 130 °C, addition of 20% water and a screw speed of 220 rpm. Two barleys (AF Cesar, AF Lucius) were hulless cultivars with a standard starch composition, while three barleys (KM 2624, KM 2460-1, KM 2460-2) were hulled waxy lines. The effect of extrusion on content of different dietary fibre fractions was determined. Also the changes of the molar mass of β-glucan were studied. Regardless of the barley genotype (standard starch or waxy), the extrusion had no significant effect on arabinoxylan content. A significantly higher beta-glucan and soluble dietary fibre content in barley cultivars with standard starch composition was observed after extrusion. The content of insoluble dietary fibre decreased significantly in all extruded flours. The molar mass of water-extractable beta-glucan increased independently of the barley variety after extrusion. But the increase in beta-glucan extractability due to extrusion was not observed.     

Changes Caused by Genotype and Environmental Conditions in Beta-Glucan Content of Spring Barley for Dietetically Beneficial Human Nutrition

Over the 5-year period (2000-2004), a significantly higher beta-glucan content was detected in the waxy varieties Washonubet, Wabet, and Wanubet (6.8-7.6%) and lines formed by crossing these varieties with malting varieties (5.8-7.1%). Conversely, the non-waxy hulled malting-type varieties Kompakt (4.0%) and Krona (4.3%) had significantly lower contents of beta-glucan. The observations also showed that concentrations of beta-glucans in 2000-2004 were significantly affected not only by varieties, but also environmental conditions in the growing periods and interactions of these two factors. Higher precipitation during the flowering time and grain filling period and lower temperatures during the flowering time in 2002 had negative effects on concentration of beta-glucans. Conversely, drier and warmer weather in 2003 enhanced the content of beta-glucans. The results show that it is possible to increase the content of beta-glucan in spring barley grain by implementing selective breeding practices. Compared to the parental malting varieties, the mean content of beta-glucans in F(4)-F(8) generations was increased by 1.8 and 2.0% by recombination in lines Kompakt x Wabet and Wanubet x Krona, respectively. Significant effect of environmental conditions and their interactions with varieties indicated the necessity to assess standard qualities of barley as a food material.     

Grain composition of Virginia winter barley and implications for use in feed,food, and biofuels production

Grain compositional components impacting barley (Hordeum vulgare L.) use in food, feed and fuel products, must be combined with improved agronomic traits to produce a commercially viable barley cultivar. Little current information is available on grain composition and variability among winter barley genotypes. This study was conducted to determine the variability among modern hulled and hulless winter barley genotypes in grain composition. Barley types varied significantly in grain and kernel weight, starch, beta-glucan, oil and ash content, but not in protein concentration. Hulless barley had significantly higher grain test weight and starch concentration than hulled and malting types, and significantly higher beta-glucan than malting barley. Hulless barley had significantly lower kernel weights, oil, and ash concentrations than hulled and malting types. Higher starch and lower fiber and ash in grain of hulless barley versus hulled feed or malting type barley are characteristics that increase hulless barley desirability. Selection for high starch concentration among all barley types is feasible and will facilitate development of barley cultivars better suited for use in feed, malt, and ethanol production.     

Phenotypic,physiological and malt quality analyses of US barley varieties subjected to short periods of heat and drought stress

Drought and heat are major abiotic stresses that significantly reduce crop yield and seed quality. In this study, we examined the impact of heat, drought and combined effect of heat and drought stress imposed during the grain filling stage in 18 US spring barley varieties. These impacts were assessed based on dry biomass, seed yield and six important malting quality traits, namely, beta-glucan, free amino nitrogen, soluble protein, refractive index, diastatic power and alpha-amylase activity. Singly applied heat or drought stress evoked a diverse set of responses among these varieties with respect to biomass, seed yield and malt quality traits suggesting these varieties can be exploited for enhancing barley production based on local conditions. Majority of the tested varieties performed poorly with reference to seed yield when the stresses were applied in combination, suggesting a lack of genetic diversity in the currently grown spring barley varieties to overcome co-occurring episodic drought and heat regimes, especially during heading stages. In the wake of global climate change, enhancing adaptive capacity of barley varieties by introducing novel germplasm into breeding programs or via new technologies is vital to sustain US barley production and meet the demands of the rapidly growing brewing industry.     

Oat Prevents Obesity and Abdominal Fat Distribution, and Improves Liver Function in Humans

Obesity is associated with a great diversity of diseases including non-alcoholic fatty liver disease. Our recent report suggested that oat, rich in beta-glucan, had a metabolic-regulating and liver-protecting effect in an animal model. In this study, we performed a clinical trial to further confirm the effect of oat. Subjects with BMI ≧27 and aged 18–65, were randomly divided into a control (n?=?18) and an oat-treated (n?=?16) group, taking a placebo or beta glucan-containing oat cereal, respectively, for 12 weeks. Our data showed that consumption of oat reduced body weight, BMI, body fat and the waist-to-hip ratio. Profiles of hepatic function, including AST, but especially ALT, were useful resources to help in the evaluation of the liver, since both showed decrements in patients with oat consumption. Nevertheless, anatomic changes were still not observed by ultrasonic image analysis. Ingestion of oat was well tolerated and there was no adverse effect during the trial. In conclusion, consumption of oat reduced obesity, abdominal fat, and improved lipid profiles and liver functions. Taken as a daily supplement, oat could act as an adjuvant therapy for metabolic disorders.     

Fractionation of oats into products enriched with protein,beta-glucan,starch, or other carbohydrates

A modified wet method was developed to fractionate ground oat groats into 4 fractions enriched with beta-glucan (BG), protein, starch, and other carbohydrates (CHO), respectively. Effects of defatting oats and centrifuge force for separation were also investigated. Results show that, depending on the two factors, nutrient concentrations in the corresponding fractions ranged 28.53–44.84% (dry matter) for BG, 72.41–92.62% for protein, 79.13–81.69% for starch, and 37.47–42.16% for other CHO. Nutrient recoveries from each fraction were 39.82–51.20% for BG, 60.36–72.08% for protein, 77.04–87.25% for starch, and 24.87–29.68% for other CHO. For the protein fraction, defatting improved the protein content but did not on its recovery. For the starch fraction, the effect of defatting was just opposite, improving the starch recovery but not the starch content. Centrifuge force increased the BG content in the BG fraction when the defatted sample was used. The cumulative recovery of each component in the combined fractions was not affected by oil removal or centrifuge force. Overall, the wet method described was relatively effective in recovering the major nutrients from oats into their respective fractions, while it alleviated the problems of viscous slurry upon mixing ground oat groats with an alkaline solvent and the difficulty of slurry separation.