甲基橙为光谱探针研究聚电解质与表面活性剂相互作用

聚电解质与两亲分子间相互作用近年备受关注［１，２］．其原因之一是这种作用与作为形成生物膜基础的类脂间的相互作用极其相似，并可看作细胞中蛋白质核酸相互作用的一种模式［３］．对众多水溶性高分子尤其是聚电解质与表面活性剂间相互作用研究表明，这种作用不仅有重要的学术意义，而且在实际应用方面也非常重要，如应用于泥浆凝聚，油井采油以及膜分离技术［４］等．在对正离子聚电解质与十二烷基硫酸钠（ＳＤＳ）水溶液相互作用的研究中，我们曾报道存在一个ＳＤＳ／正离子（摩尔比）非常窄的区域，溶液粘度突然上升，超过这一区域…     

YEAST FLOCCULATION: A NEW METHOD FOR CHARACTERISING CELL SURFACE INTERACTIONS

Flocculation is a property of yeast cells that has been traditionally used in industrial fermentations, especially in the brewing and wine industries. It is a cell wall interaction and an increase in flocculation is strongly correlated with an increase in cell surface hydrophobicity . Methods to assay yeast cell surface hydrophobicity are only qualitative and while electrostatic interactions can play an important role, they are not always taken into account . In this work, a simple and accurate method based on contact angle measurements is described to determine yeast cell surface hydrophobicity. With this method, it is possible to quantify yeast cell surface hydrophobicity by determining the free energy of interaction between cells and water molecules. Several yeast strains with different flocculation characteristics have been used to validate the method .     

Yeast Proteolytic Activity During High and Low Gravity Wort Fermentations and its Effect on Head Retention

The aim was to discover the effect of high gravity brewing on yeast protease activity during fermentation, on the loss of hydrophobic polypeptides from wort during fermentation, and on the foam stability of stored beer. The hydrophobic polypeptide content of low (10° Plato) gravity worts showed a steady decline throughout fermentation, but for the 20° Plato wort there was a rapid decline over the first 8 days of fermentation, followed by little change over the remaining period. The decrease in hydrophobic polypeptides was greater in the high gravity fermentation. Proteinase A increased during fermentations with the highest levels being present at the end of fermentations. High gravity fermentations exhibited levels of yeast protease that from the 3rd to 11th day of fermentation were at least twice the values of the low gravity fermentations. The high gravity brewed beer contained significantly higher levels of proteinase A activity than the low gravity brewed beer. The inclusion of FERMCAP™, an antifoam, in high gravity wort did not affect either the hydrophobic polypeptide levels or foam stability of the resultant beer. This suggests that proteinase A, rather than fermenter foaming, must be the major contributor to the lack of foam stability of high gravity brewed beer. Head retention measurements conducted on the high and low gravity brewed bottled beers, over a five month period, demonstrated a steady decline in foam stability for both beers. The declines in head retention did not occur in high and low gravity beers that had been pasteurised.     

氟碳超支化醇酸的制备及其涂料性能研究

以双季戊四醇、二羟甲基丙酸、油酸、全氟辛酸为原料合成了氟碳超支化醇酸树脂。采用了IR、TG、AFM和化学滴定等方法对产物进行了表征和分析。用氨基树脂747作固化剂,150℃下烘烤20min,得到的烤漆平整光亮,综合性能优良,涂膜有很好的疏水性。     

Mixed matrix metal–organic framework membranes for efficient CO2/N2 separation under humid conditions

Mixed matrix metal–organic framework (MOF) membranes show excellent application prospects in gas separation. However, their stability in various practical application scenarios is poor, especially under humid conditions. Herein, we encapsulated a hydrophobic ionic liquid (IL) into the cavity of MOFs, which effectively mitigated the competition between H₂O and CO₂ in humid gas mixtures, leading to stable and high-performance gas separation. For this reason, the resulting membranes using polymer of intrinsic miroporosity-1 (PIM-1) as a polymer matrix show good CO₂/N₂ separation performance and long-term test stability under humid environment. In particular, the 20 wt% IL-UiO/PIM-1 shows a high permeability of 13,778 Barrer and competitive CO₂/N₂ separation factor of ~35.2, transcending the latest upper bound. Besides, the according membrane module exhibits slightly decreased CO₂ permeability and selectivity, promoting the application of self-supporting membranes. This work provides a reliable strategy for the rational design of MOF-based hybrid membranes under extreme conditions.     

Mechanisms of Syneresis in Rennet Curd without Mechanical Treatment

An original method for syneresis evaluation was developed, based on image analysis which enabled direct monitoring of curd shrinkage. Image analysis was employed in combination with the customary tracer method to follow the effects of cutting on curd syneresis. The two methods were then utilized to study curd syneresis in the presence of ethanol, a solvent less polar than water. Curd syneresis was reduced in the presence of diluted ethanol which led to the hypothesis that the mechanism which causes rennet curd to synerese probably relates to changes in protein conformation, essentially due to hydrophobic bonding.     

疏水和超级疏水整理的新测试方法

目前基于全球化的世界经济形势迫使西欧工业在高品质领域更多地革新和发展,并把大量的廉价产品的生产向低工资国家转移.因此,高效能产品和高度发展的制造工艺在欧洲赢得了越来越重要的意义.于是,至今而论,进一步改善那些高品质产品,并根据情况尽量生产高价格产品仍然是正确的.     

改性羰基铁粉制备及其在蓝光固化磁控超疏水薄膜中的应用

针对超疏水涂层膜在固化过程中功能性颗粒的不受控运动以及传统的热固化能耗高、耗时长的缺点,通过对羰基铁粉进行改性,并将磁控技术和蓝光固化技术相结合构筑超疏水薄膜。分析改性剂质量比、用量、pH值以及温度对羰基铁粉改性效果的影响,确定最佳改性工艺;研究了磁场强度对光固化薄膜表面接触角以及形貌的影响规律。结果表明:当改性剂3-(甲基丙烯酰氧)丙基三甲氧基硅烷与1H,1H,2H,2H-全氟葵基三甲氧基硅烷质量比为1:3,质量分数为20%,pH值为6,温度为75 ℃,时间为1.5 h时,羰基铁粉表面改性效果最佳,其活化度达到96%,Zeta电位绝对值由22 mV提高至43 mV;随着磁感应强度的增加,薄膜表面接触角不断增加,当磁感应强度为75 mT时,超疏水薄膜的表面接触角达到157.6°,滚动角为6°,符合超疏水标准。     

淀粉疏水改性研究进展

传统变性淀粉只有单一的亲水性质,淀粉的疏水改性成为该领域的研究热点之一。介绍了国内外烷基脂肪酸淀粉酯和烯基琥珀酸淀粉酯的研究现状及存在的问题,认为对烷基脂肪酸淀粉酯要重点研究低成本、环境友好制备高取代度的产物;而对烯基琥珀酸淀粉酯要重点研究低葡萄糖值的酶解产物。前者可以通过改变淀粉颗粒结构来改善,后者可以通过减少酶用量和作用时间并采用挤出技术或滚筒干燥等途径实现。     

HYDROPHOBIC POLYPEPTIDE EXTRACTION DURING HIGH GRAVITY MASHING— EXPERIMENTAL APPROACHES FOR ITS IMPROVEMENT

The aim was to establish if a substantial increase in hydrophobic polypeptides could be achieved during high gravity mashing. When worts with gravities ranging from 5–20°P were analysed for hydrophobic polypeptide content it was found that there was no appreciable increase in hydrophobic polypeptide levels. Remashing of the spent grains from low and high gravity mashes demonstrated that this resulted from inefficient extraction of hydrophobic polypeptide levels during the mashing process. For example, wort produced from remashed high gravity spent grains contained 150 mg/L hydrophobic polypeptides compared to only 10 mg/L in the low gravity remashed spent grains. Experiments were conducted, employing standard mashing techniques, in an attempt to increase the extraction of hydrophobic polypeptides during high gravity mashing. Thus the use of gypsum, proteolytic stands, varying liquor to grist ratios and wheat malt addition were all investigated for their effect on hydrophobic polypeptide extraction during high and low gravity mashing. Wort analysis demonstrated that none of the techniques employed had a significant effect on hydrophobic polypeptide extraction. When wort from remashed spent grains was used as mashing in liquor for a fresh mash and the resultant worts analysed for hydrophobic polypeptides it was observed that no increase in hydrophobic polypeptide extraction was achieved. For example, wort from the remashed high gravity spent grains, containing 140 mg/L hydrophobic polypeptides, when used as mashing-in liquor, produced no increase in hydrophobic polypeptide levels in the resultant high gravity wort (230 mg/L) when compared to a high gravity wort produced using distilled water as mashing-in liquor (255 mg/L). It is therefore concluded that a saturation point has been reached and no more hydrophobic polypeptides can be extracted during mashing regardless of the procedures employed.