高能机械球磨法制备高质量纳米β-SiC粉体

使用高能机械球磨法．首次以单质硅和石墨的混合粉体为初始原料,制备出了高质量的β-SiC纳米粉体。对球磨产物进行了XRD和TEM等表征,结果表明：球磨10h后,石墨粉完全非晶化,大部分硅粉也已经非晶化,而且已经有β-SiC纳米粉生成;球磨20h后,硅粉和石墨粉完全反应生成了单相的β-SiC纳米粉,平均晶粒尺寸约为20nm,但是团聚比较明显;球磨40h后的样品,平均晶粒尺寸约为12nm,而且样品分散性较好,为均匀的球形颗粒;继续增加球磨时间．虽然样品晶粒尺寸稍有减小。但是团聚又逐渐变明显,而且样品中混入铁的量逐渐增加。     

酶解-球磨法制备微细化淀粉的性质研究

传统微细化小颗粒淀粉的制备采用原淀粉直接球磨的方法,耗时长,能耗高,产物易糊化。采用先酶解再球磨的新工艺制备微细化小颗粒淀粉,并与玉米原淀粉、原淀粉球磨淀粉的性质进行比较。结果表明:玉米原淀粉的表面积平均粒径为12.90μm,原淀粉球磨淀粉的表面积平均粒径略有增大,而酶解-球磨淀粉的表面积平均粒径显著降低;酶解-球磨淀粉的结晶结构受到一定程度的破坏,部分偏光十字消失,双折射强度减弱,结晶度显著降低。     

Thermo-mechanical rice flour modification by planetary ball milling

Planetary ball milling is presented as an alternative way to improve the native flour properties by physical modification. A grinding protocol was developed by combination of grinding and pause stages. The effect of rotational speed (450–650 rpm) and milling time (10–20 min) on flour properties were determined using RSM method. The effect of milling conditions on flour attributes was significant. With increasing milling speed and time a significant increase in damaged starch, water-absorption and solubility indexes was observed. Changes in functional attributes, intrinsically related to structural and morphological properties of rice flour, were satisfactorily correlated with crystallinity loss, specific surface area and gelatinization degree. Modified rice flours presented pre-gelatinized characteristics which can offer new opportunities for flour applications, for example as ingredient for instant meal product. Flour modification can be controlled by selecting milling conditions. The distinctive characteristic of the planetary ball mill was the fast speed with which the modified flour was obtained which presented intermediate characteristics in relation with native and amorphous state.     

球磨处理对南瓜籽蛋白结构的影响

为探究球磨处理促进南瓜籽蛋白酶解的机制,以未处理的南瓜籽蛋白为对照,研究球磨处理对南瓜籽蛋白二级、三级结构,溶解性,热力学特性以及微观结构的影响。结果表明：南瓜籽蛋白经不同时间球磨处理后,其结构有所改变;傅里叶变换红外光谱显示,球磨处理造成南瓜籽蛋白二级结构发生变化,球磨处理15 min时,α-螺旋和无规卷曲结构分别由处理前的19.98%和14.28%增加至20.59%和16.51%;内源荧光光谱和紫外吸收光谱分析结果表明,球磨处理后的南瓜籽蛋白三级结构变得更加疏散;球磨处理提高了南瓜籽蛋白的溶解度,球磨处理5 min时,溶解度提高了16.92百分点;DSC图谱表明,球磨处理使南瓜籽蛋白的变性温度降低;粒径分布和扫描电镜图显示,球磨处理15 min时,峰顶的粒径从217.3 nm下降至159.8 nm,整体结构被破坏。综上,适度球磨处理可以改变南瓜籽蛋白分子结构,使酶容易与南瓜籽蛋白的酶切位点结合,从而促进酶解。     

不同热处理条件下羊血浆蛋白体外模拟消化研究

目的 研究不同热处理条件下羊血浆蛋白的体外模拟消化特性及其蛋白质二级结构的变化规律。方法 采用胃蛋白酶对热处理后的羊血浆蛋白进行体外模拟消化,利用茚三酮法、十二烷基硫酸钠聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate polyacrylamide gel electrophoresis,SDS-PAGE）、表面电位（Zeta potential）及粒径、傅立叶变换红外光谱（Fourier Transform infrared spectroscopy,FTIR）等表征羊血浆蛋白的水解程度及消化产物的结构特性。结果 热处理可使羊血浆蛋白消化产物水解度增加,90℃热处理时水解度达到最大值,热处理可产生更多的低分子量组分,消化降解更为完全。90℃热处理时羊血浆蛋白消化产物的粒径分布单一,聚集程度最高。70~90℃热处理组的红外光谱显示酰胺Ⅰ带向低波数方向有不同程度红移,随着热处理程度的增加,羊血浆蛋白消化产物中α-螺旋结构含量先增加后减少,β-折叠结构含量总体降低。结论 热处理对羊血浆蛋白体外模拟消化均有一定的促进作用,从蛋白质变性的角度考虑,羊血浆蛋白的热处理强度不宜超过90℃ 20 min。     

Release of ‘soluble’ lignin fragments from orchardgrass during its passage through the rumen

Soluble lignin fractions were isolated with 90% (v/v) aqueous dioxane from the rumen digesta and faeces of a heifer fed on orchardgrass harvested at the pre-heading stage. Chemical analysis, UV and IR spectra indicated that the soluble lignin fractions were composed mostly of lignin components. The two solube lignin fractions showed wide distributions of molecular weight and had number-average molecular weights of 650–690 and weight-average molecular weights of 1450–1480. The results showed that, part of the orchardgrass lignin fed was released in the rumen as soluble lignin fragments with different molecular weights and excreted in the faeces possibly without further significant modifications.     

球磨处理对小麦淀粉理化性质的影响

该文以小麦淀粉为原料,采用行星式球磨机对小麦淀粉进行机械损伤,通过对不同球磨处理时间下小麦淀粉的损伤淀粉含量、沉降体积、析水率、透明度以及溶解度和膨润力等指标的测定,得出:随着球磨时间的延长,小麦淀粉的溶解度、膨润力、析水率和损伤淀粉含量均显著增加,淀粉糊的峰值黏度、谷值黏度、最终黏度、衰减值和回生值均呈明显下降趋势;凝胶的硬度、脆度、黏附性、弹性和咀嚼性也随球磨时间的增加而下降。     

球磨对绿豆淀粉颗粒形态和理化性质的影响

采用行星式球磨机对绿豆淀粉进行改性研究,以球磨时间为控制变量,对比球磨0、1、2、4、6h时绿豆淀粉颗粒形态和淀粉糊理化性质的变化.结果表明,球磨处理后绿豆淀粉颗粒表面出现凹痕,表皮变皱逐渐破裂,随时间的增加颗粒变得扁平并有抱团现象,偏光十字逐渐模糊直至消失;随球磨时间的延长,损伤淀粉和直链淀粉含量增加,淀粉糊溶解度、透明度和析水率均显著增大,淀粉糊峰值黏度、谷值黏度、最终黏度、回生值和衰减值均呈下降趋势.     

葛花粉体高效球磨制备技术及其醒酒活性测定

为探究葛花粉体粒径与功效释放速度的相关性及其醒酒机理,通过比较4种不同粉碎方法处理得到的植物本体、常规粉体、Ⅰ级粉体、Ⅱ级粉体在总物质溶出度、黄酮溶出量及乙醇脱氢酶(ADH)体外活性实验方面的差异性,发现4种粉体均可在体外激活乙醇脱氢酶,但在总溶出度上Ⅱ级粉体优于Ⅰ级粉体,其次是常规粉体和植物本体,其瞬时溶出度可达到植物本体的8.6倍。在黄酮溶出量和ADH激活率上也呈现相同趋势,Ⅱ级粉体黄酮溶出含量较植物本体提高57.98%,激活率为本体的2倍。实验表明,采用高效球磨技术制备的葛花Ⅱ级粉体较其他粉体均呈现出最优实验结果,且其醒酒作用机制与其能激活乙醇脱氢酶有关,为开发新型醒酒功能食品提供理论依据。     

Roles of structural phenylpropanoids in forage cell wall digestion

Phenolic constituents (lignins and phenolic acids) and carbohydrates are assembled in a tight architecture which differs according to the plant species. During cell wall digestion, the hydrolysis kinetics differ between carbohydrates and seem to depend chiefly on the content and organisation of tissue phenolics. Among the phenylpropanoids, ferulic acid is released more quickly than p-coumaric acid. Lignins remain largely in the cell walls. They also undergo transformations, chiefly solubilisation as lignin-carbohydrate complexes. The limiting effect of lignins on cell wall degradation increases with increasing content. However, their effect on degradation might also depend on qualitative factors such as lignin structure and polymer organisation in walls and tissues. When various grasses (normal and selected genotypes), or grasses and legumes are compared, correlations between certain factors such as lignin uncondensed fraction, syringyl units or phenolic acids contents and cell wall degradation emerge but not clear causal relationship has been shown. Nonetheless, other structural characteristics, related to the alkali reactivity of lignins, seem to have a stronger influence on cell wall degradation. Phenylpropanoids seem to act mainly as a physical and (bio)chemical barrier to the action of the microbial enzymes. In addition, their reactivity as phenolic compounds and their hydrophobicity seem to play a role. Digestion is not limited only by phenolics. The factors that limit glycanolysis—the accessibility, crystallinity and capillary structure of cellulose and the branching of hemicelluloses—seem to have little or no effect on cell wall degradation in vivo. In contrast, other antiquality substances (tannins, cutin and silica), plant antomy, environmental factors, factors modulating microbial growth and animal physiology influence cell wall utilisation. Future research in this field should focus on the effects of phenolic structure and of cell wall and tissue organisation on carbohydrate degradation.     

Effect of including barley or molassed sugar beet feed in grass silage diets on their digestion by cattle and sheep

The objective of the experiment was to compare the digestion of barley, a starch-based feedingstuff, with molassed sugar beet feed (SBF), a high-fibre, sugar-containing feedingstuff, when fed to cattle and sheep receiving silage. There were between-species differences in rumen measurements. Sheep had higher mean daily rumen ammonia-N concentrations; the molar proportions (mmol mol^?1 total rumen volatile fatty acids) of propionic acid were higher and those of n-butyric acid lower in sheep than in cattle. The feeding of barley was associated with increased rumen populations of protozoa and increased rumen ammonia-N concentrations compared with the feeding of SBF. There were no significant differences between the diets fed in whole tract or rumen digestion of organic matter or nitrogen. However, feeding SBF tended to increase the quantities of non-ammonia-N and microbial N entering the small intestine daily: feeding barley did not improve N flow to the small intestine.     

Comparative compositional and functional characterisation of rye varieties and novel industrial milling fractions

This work aimed to collect and study all milling fractions generated during an industrial rye milling technology and to select nutritionally promising subfractions for further investigations (chemical composition and rheological behaviour) also considering their yield. To investigate the varietal effect, four rye samples were examined and applied in the milling experiments. The results showed great variability of technological properties (mainly in viscous behaviour) among rye samples. Generally, subfractions had higher protein, lipid, total and soluble dietary fibre content than white flours, and several subfractions provided higher values even than wholemeal flours. Significant differences were found between the fractions in the mixing and viscous behaviour, which could be explained principally by the variable dietary fibre content and composition, however, the effect of protein content was found also prominent. The results pointed out that alternative milling products with favourable composition and technological properties can be produced by collecting appropriate subfractions.     

Apparent inhibition to digestion by lignin in normal and brown midrib stems

Lignin, a cell wall component, limits digestibility of plant cell walls. Brown midrib (bmr) mutants of forages have lignin with altered chemical composition compared with their normal counterparts. The objectives of this study were to determine if bmr lignin is more inhibitory to digestion than is normal lignin and if bmr has a consistent effect on rate of digestion across species and environments. Extent and rate of in-vitro cell wall digestion of normal and bmr stems of sorghum (Sorghum bicolor (L) Moench, two comparisons), millet (Pennisetum americanum (L) Leeke) and maize (Zea mays L, two comparisons) were determined. Samples were incubated in rumen fluid, and data were fitted with a first-order, nonlinear model to estimate concentrations of potentially digestible neutral detergent fibre (PDNDF), digestion rate of PDNDF, concentration of indigestible residue (IR), and lag time before digestion. The NDF, acid-detergent fibre (ADF), and acid-detergent lignin (ADL) analyses were conducted sequentially on undigested samples. The IR: ADL ratio was 37% greater for bmr than for normal plants, which indicates that bmr lignin inhibits digestion more than normal lignin per unit of lignin. Digestion rate of PDNDF was faster in bmr than in normal counterparts in one of the two sorghum comparisons (difference of 59%) and in the millet comparison (difference of 27%), but in neither maize comparison. The bmr mutants were lower than normal genotypes in NDF (9%) and ADL (47%) concentrations. The PDNDF concentration was 19% greater for bmr than for normal lines. Thus, decreased lignin concentration in bmr mutants increased the extent of NDF digestion but did not consistently increase the rate of digestion.     

Fractionation and characterization of ball‐milled and enzyme lignins from abaca fibre

An Erratum has been published for this article in Journal of the Science of Food and Agriculture 79(15) 1999, 2122. Ball‐milled and enzyme lignins were produced from abaca fibre via ball milling for 6 days followed by cellulase treatment for 3 days. The crude lignin preparations were fractionated into milled lignin (ML), enzyme lignin (EL), hemicellulose‐rich milled lignin (HRML), and lignin‐rich enzyme lignin (LREL) fractions using a two‐step precipitation method instead of a traditional ether precipitation procedure. The yield and chemical composition of the resulting lignin samples are reported. The ML and EL fractions contained low amounts of associated neutral sugars (2.0–3.3%) and uronic acids (1.4–1.5%), and showed relatively low average molecular weights (2500–2660), while the LREL and HRML fractions contained large amounts of bound polysaccharides (35.6–38.3%), and showed high molecular weights (8800–25000). The four lignin fractions are composed of a large proportion of syringyl units with fewer guaiacyl and p‐hydroxyphenyl units. The ML is mainly composed of β–O–4 ether bonds between the lignin structural units. The less common β–β, β–5 and 5–5′ carbon–carbon linkages are also present in the lignin molecules. It was found that uronic acids and 41–63% of p‐coumaric acids are esterified to lignin in the three lignin‐rich fractions of ML, EL and LREL. This level increased to over 90% in the hemicellulose‐rich fraction of HRML. For ferulic acids, 92–97% were found to be etherified to lignin in the three lignin‐rich fractions of ML, EL and LREL, while in the hemicellulose‐rich fraction of HRML this reduced to only 13%, suggesting that a majority of the ferulic acids are esterified to hemicelluloses or lignin in this fraction. © 1999 Society of Chemical Industry     

掺锰氢氧化镍的机械球磨工艺及电化学性能研究

采用机械球磨法,通过确定最佳的工艺条件(锰掺杂量为20%,球磨时间15 min,球料比8∶1,球磨机转速350 r/min,陈化温度70℃),制备出电化学性能良好的掺锰Ni(OH)2材料.经X射线衍射(XRD)和扫描电子显微镜(SEM)测试,结果表明,掺锰氢氧化镍保持了β-Ni(OH)2的晶体结构,颗粒呈不规则形状,粒径约5μm.恒电流充放电测试结果表明,该材料的0.2 C放电比容量达到261 mAh/g,经过300次1 C循环后容量仍保持初始容量的90%.     

Role of particle size and forage quality in digestion and passage by cattle and sheep

Diminution of forage particles includes mastication, chewing, and digestion. In rumen of cattle and sheep fed all forage diets, particle size can range from 200 to over 1200 microns. Particle size reduction to about less than 1200 microns must occur before passage. Dietary particle size may influence rumen particle size, but mastication and rumination minimizes differences among diets. Ruminants expend considerable effort to move digesta. Density, cell wall percentage, osmotic pressure, and pH may affect propulsion. Dense particles may sink to the bottom and resist escape. Cell wall may reduce digestion and passage. Osmotic pressure or pH may affect digestive efficiency and rhythm of intestinal tract muscles. Chewing, exercise, physiological functions, and body size may also affect the reduction of forage particle size. More effort is necessary to chew high than low fiber diets. Young cattle (less than 225 kg) lack rumination capability and body size to process forage particles efficiently. Exercised sheep (26,400 kg-m/d) ate less forage and ruminated less than controls. Other body functions, such as lactation, appear to influence chewing patterns and rumination. These relationships are poorly understood at best and need additional intensive examination.     

Structural changes in cow,goat, and sheep skim milk during dynamic in vitro gastric digestion

Coagulation of milk in the stomach is the first crucial step in its digestion. Using a human gastric simulator, the dynamic gastric digestion of goat and sheep skim milk were compared with that of cow skim milk, focusing particularly on their physical characteristics. The gastric contents were analyzed for changes in dry matter and microstructure, and the extent of protein digestion. The study revealed that the skim milk from all species formed a curd within the first 15 min of gastric digestion, at which time the pH was ~6.1 to 6.3. Compared with cow skim milk, the dry matter contents of the clots formed from goat and sheep skim milk were lower and higher, respectively, which was due to the differences in their total solids and protein contents. Microstructural analysis showed that, as digestion progressed, the clot structure became more cohesive, along with a decrease in moisture content, which in turn affected the breakdown and hydrolysis of caseins by pepsin; this phenomenon was similar for milk from all species. However, the extent of moisture retained in the sheep skim milk clot appeared to be lower than those of the cow and goat skim milk clots. In addition, the relative firmness of the sheep milk clot was higher than those of the cow and goat milk clots at the end of gastric digestion. The pattern of protein hydrolysis by pepsin was similar for the milk of all species, despite the differences in the proportions of different proteins. The study provided insight into the coagulation kinetics of goat and sheep skim milk under in vitro gastric digestion conditions.