小麦细胞壁结构对水分迁移的调控作用

为探明小麦糊粉层细胞壁这种由阿拉伯木聚糖和β-(1-3)(1-4)葡聚糖组成的复合多层结构对水分的调控作用,研究了小麦糊粉层细胞壁结构对水分吸收速率、干燥速率和水分子移动性的调控作用。结果表明:通过环境扫描电镜(SEM)筛选出糊粉层最厚的周麦22和糊粉层最薄的中麦895,大麦和青稞作为对比,其中大麦细胞壁厚度是中麦细胞壁厚度的1. 49倍。通过比较周麦22、中麦895、大麦和青稞的糊粉层厚度与水分吸收速率、干燥速率的关系,说明了糊粉层细胞壁与吸水、干燥速率呈负相关。通过低场核磁共振检测发现:相同吸水条件下,糊粉层细胞壁越厚的样品其体内含水量越低但体内水分子的移动性越好;在干燥条件下,糊粉层细胞壁越厚的样品其体内含水量越高且水分子的移动性越好。因此,小麦糊粉层细胞壁结构对水分迁移具有显著调控作用。     

小麦糊粉层结构及特性研究进展

小麦是人们日常生活不可或缺的粮食作物,小麦糊粉层则聚集了小麦籽粒大部分的营养与精华。糊粉层不仅在小麦籽粒发育时起着重要作用,更是对人体健康有着极大的益处。对糊粉层的营养组成进行介绍,并对糊粉层的生理结构、功能特性及对食品影响等几个方面进行概述。     

微生物细胞壁结构及结合真菌毒素的研究进展

生物去除真菌毒素是目前的研究热点之一。除了微生物产酶对毒素进行化学修饰后降解为无毒或者毒性较低的产物外,微生物细胞对毒素的吸附与结合作用也占有一定的比例,这与微生物表面组成和结构特征相关。本文就微生物细胞表面结构及吸附毒素的国外研究进展进行概述,重点阐述相关研究现状、黏附机理和影响因素,旨在为真菌毒素的去除研究提供参考。     

小麦糊粉层分离及产品开发研究进展

小麦中大部分的生物活性物质多聚集于糊粉层中,主要论述了小麦糊粉层的组成、分离技术、相关产品研究。大力开发糊粉层产品,能够改善人们的营养结构,促进民众健康水平,提升粮食利用率、延长小麦产业链。对小麦糊粉层的研究和开发利用,使其能够广泛应用于食品工业中。     

英国的小麦剥皮制粉工艺

本文介绍一种被称之为Trigotec的英国小麦剥皮制粉工艺。应用该工艺可提高小麦的精制粉和麦心出率,同时产生的副产品也不同于传统工艺的。它品种较多,每一种副产品在营养利用方面都有其专门的用途。     

小麦籽实糊粉层与面粉品质的关系

本文从小麦籽实糊粉层细胞组织具有丰富的营养成分方面进行了分析；对改良和强化优质面粉烘焙品质及保持天然营养成分进行了科学的论证。     

小麦籽实的形态结构与制粉方法的配合

配合小麦籽实的三大组成部分──籽实皮、胚乳和胚的形态和结构，进行解剖型模式制粉方法改革，是合理利用小麦资源的一条重要途径。     

保加利亚乳杆菌细胞壁蛋白酶基因克隆及结构分析

本文以保加利亚乳杆菌基因组为模板,利用PCR的方法扩增细胞壁蛋白酶基因(prtB),并且利用GeneBank数据库和生物软件对prtB进行对比和生物信息学分析,预测基因片段的相似性、表达出蛋白酶的蛋白大小、二级结构和膜结合性等性质。结果表明,测序后比对发现扩增片段与模板保加利亚乳杆菌prtB相似性为100%,证明基因片段未发生突变;prtB与德氏乳杆菌德氏亚种基因相似性为96%,与德氏乳杆菌乳酸亚种(Lactobacillus delbrueckii)基因相似性为82%,具有一定的保守性和特异性。prtB基因G+C含量为47.49%,A+T含量为52.51%,编码1831个氨基酸,分子量为3338.7 kD,将此蛋白命名为PrtB,等电点pI为8.76。保加利亚乳杆菌的PrtB为亲水性稳定蛋白,总平均亲水性为-0.583,有28个Ser、9个Thr和25个Tyr可能成为蛋白激酶磷酸化的作用位点,该蛋白为细胞外蛋白,其二级结构以不规则卷曲为主,其值为55.11%,α-螺旋和β-折叠仅占21.30%和23.59%。     

把握小麦价格因素，调控粮食价格

通过考察20世纪80年代以来中国小麦价格的历史演进.特别是20世纪90年代以来多种因素对粮食的影响,全面考察影响小麦的价格因素,得出影响粮食价格的关键因素.通过对小麦市场的考察,为粮食市场的价格预测,国家的粮食价格调控提供参考.     

小麦糊粉层粉的微波辐照处理条件优化

为了降低小麦糊粉层粉中的脂肪酸值,在不同条件下对其进行微波稳定化处理。以微波功率、辐照时间、物料水分含量设计单因素试验,以脂肪酸值为指标,采用正交试验对处理条件进行优化。结果表明,在微波功率600 W、物料水分含量20%、辐照时间180 s的处理条件下,小麦糊粉层粉的脂肪酸值达到最低值。经微波辐照后,小麦糊粉层粉中的脂肪酶和脂肪氧化酶的内源酶活度、微生物菌落总数显著降低(P<0.05),提高了小麦糊粉层粉的安全性;同时,在植酸含量、总酚含量有所降低的情况下,微波辐照后小麦糊粉层粉的总抗氧化能力仍然显著增加(P<0.05)。     

Biochemical characterization of wheat straw cell wall with special reference to bioactive profile

The core objective of the current study was to extract and characterize the wheat straw cell wall for its nutritional and bioactive profile. For the purpose, four different wheat straw varieties namely Ujala-16, Johar-16, Gold-16, and Galaxy-13 were procured from Ayub Agriculture Research Institute, Faisalabad, Pakistan. The whole research was conducted in three different phases. In first phase, nutritional composition and mineral profile of straw of different wheat varieties were determined. In second phase, wheat straw cell wall of different varieties was isolated and characterized for its important bioactive constituents, such as lignin, cellulose, hemicelluloses, phytosterol, and policosanol (PC) content. Results showed that straw of different wheat varieties contained 7.75–9.24, 3.98–5.06, 3.43–3.98, and 1.60–2.24 g/100 g moisture, ash, protein, and fat contents, respectively, whereas potassium, calcium, phosphorus, and magnesium were 1.19–2.03, 0.10–0.79, 0.10–0.98, 0.03–0.98 ppm, respectively. Moreover, lignocellulosic mass: cellulose 37.75–38.18 g/100 g raw material, lignin 15.67–16.07 g/100 g raw material, hemicelluloses 28.25–28.98 g/100 g raw material, was present in wheat straw and varied significantly among different varieties. In addition, phytosterol ranged from 854 to 1176 mg/kg in straw of different wheat cultivars, whilst PC from 196.09 to 236.48 mg/kg. Conclusively, wheat straw was an excellent source of many important bioactive moieties especially lignocelluloses and could have functional use.     

Texture of Chinese water chestnut: Involvement of cell wall phenolics

Chinese water chestnuts (CWC) fail to soften during cooking. This is due to thermal stability of cell wall polymers involved in cell-cell adhesion. Information concerning these polymers was obtained by subjecting CWC tissues to a range of chemical and biochemical treatments designed to cleave selectively cell wall chemical bonds. Neither chelating agents nor weak base (Na₂CO₃, 0·05 M ) facilitated vortex-induced cell separation (VICS) in fresh or canned tissues. However, VICS could be induced after extraction in dilute, cold alkali (0·1 M KOH), dilute hot acid, or a purified, specific endoxylanase. The CWC cell walls also exhibited considerable pH-dependent autofluorescence which originated mainly from ferulic acid and its derivatives. This disappeared during alkali-induced VICS. The results are consistent with the involvement of ferulic acid-containing cell wall hemicelluloses in the thermal stability of cell-cell adhesion and therefore texture in CWC tissues.     

Degradation of cell wall material of apple and wheat bran by human faecal bacteria in vitro

The effect of the structures of plant cell walls and their component polymers on the degradability of dietary fibre by bacteria of the human colon was investigated by inoculating culture media containing cell wall materials of apple and wheat bran with slurries of human faeces which were then incubated for periods of up to 72 h. In the apple substrates the amounts of pectic polysaccharides were extensively depleted after 12 h, and after 24 h over 90% of the initial carbohydrate had been degraded. Material which remained after incubation was probably comprised of highly branched fragments of rhamnogalacturonans, cross-linked by phenolics and proteins, highly branched fragments of cross-linked xyloglucans, and degraded cellulose. In wheat bran the aleurone layer was preferentially degraded, but the glucuronoarabinoxylans, which were cross-linked by phenolic groups, and the lignified outer layers of the bran were very resistant to attack. Bacteria adhered mainly to the broken or damaged surfaces of the plant cell walls, and in the more resistant tissues only penetrated the intercellular regions.     

Cell wall porosity and available surface area of wheat straw and wheat grain fractions

Interactions between polymers define many of the physical properties of plant cell walls. The most important of these are available surface area and the related measures of pore size and distribution. Gas adsorption and mercury porosimetry methods for the measurement of these parameters in wheat straw, whole wheat grain and grain fractions were compared. All of the samples examined had a very low surface area regardless of the means of measurement. However mercury porosimetry gave values 10-fold greater than gas adsorption. It is suggested that the assumptions made about pore structure necessary for the use of mercury porosimetry do not hold for plant material and that closed pore systems were distorted by the very high pressures involved. Gas adsorption gave a more realistic assessment of 2–8 m² g⁻¹ with grain having a lower available surface than vegetative walls. Pore regimes in both grain and straw were very similar and were determined in grain by the bran fraction. Little structure could be found associated with the starchy endosperm. Pores with radii of 1·5–3 nm predominated in wheat cell walls. These are below the size which would allow free penetration of the wall by degrading enzymes. ©1997 SCI     

Biodegradation of plant cell walls,wall carbohydrates,and wall aromatics in wheat grown in ambient or enriched CO2 concentrations

Mature internodes from wheat (Triticum aestivum L) grown in control (ambient at c 370 μnol mol^?1) or enriched (to 550 μmol mol^?1) concentrations of atmospheric CO₂ in the free-air CO₂ enrichment (FACE) system were analyzed for potential changes in biodegradation of constituents due to predicted increases in atmospheric levels of CO₂. The first internodes below the grain were incubated with the lignocellulose-degrading white rot fungus, Phanerochaete chrysosporium K-3, or incubated without microorganisms. Plant samples were then analyzed for dry weight loss, disposition of specific cell types to biodegradation using electron microscopy, carbohydrates and lignin using solid state NMR spectroscopy, and ester-and ether-linked aromatics using gas chromatography. Phanerochaete chrysosporium extensively degraded stems cells (c 75%) and both carbohydrate and aromatic portions of the wheat stems; proportionately more carbohydrates were removed by the fungus from the stems. Enriched CO₂ did not affect the chemical composition of wheat stems or the biodegradation by P chrysosporium of plant cell walls or wall components for the most part. Data from various methods all indicated that enriched CO₂ did not substantially alter the biodegradation of wheat cell wall internodes or wall components. Evidence was not found for an influence on C cycling due to CO₂ concentrations in this study.