Charge transport and luminescent properties of PMMA-dehydrate nanotubed titanic acid nanocomposites

In this paper, we doped p-type conductivity dehydrated nanotubed titanic acid (DNTA) into insulator polymer poly(methyl methacrylate) (PMMA). The electric properties of this nanocomposite were investigated. The photoluminescence efficiency of fluorescent dye 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) in PMMA matrix was enhanced by doping with DNTA. Moreover, screen effect by DNTA with high permittivity caused the emission from DCJTB to be blue-shifted.     

Controlled retting of hemp fibres: Effect of hydrothermal pre-treatment and enzymatic retting on the mechanical properties of unidirectional hemp/epoxy composites

The objective of this work was to investigate the use of hydrothermal pre-treatment and enzymatic retting to remove non-cellulosic compounds and thus improve the mechanical properties of hemp fibre/epoxy composites. Hydrothermal pre-treatment at 100 kPa and 121 °C combined with enzymatic retting produced fibres with the highest ultimate tensile strength (UTS) of 780 MPa. Compared to untreated fibres, this combined treatment exhibited a positive effect on the mechanical properties of hemp fibre/epoxy composites, resulting in high quality composites with low porosity factor (α_pf) of 0.08. Traditional field retting produced composites with the poorest mechanical properties and the highest α_pf of 0.16. Hydrothermal pretreatment at 100 kPa and subsequent enzymatic retting resulted in hemp fibre composites with the highest UTS of 325 MPa, and stiffness of 38 GPa with 50% fibre volume content, which was 31% and 41% higher, respectively, compared to field retted fibres.     

Selected Saccharomyces cerevisiae yeast strains and accurate separation of distillate fractions reduce the ethyl carbamate levels in alembic cachaças

Ethyl carbamate (EC) is a potentially toxic compound that may be present at concentrations above maximum limits established in alcoholic beverages, such as cachaça. Most traditional alembic cachaça is produced on a small scale using empirical knowledge. The fermentation step is conducted using yeasts that are endogenous to the sugar cane, and the distillation process is relatively uncontrolled. In this study, gas chromatography coupled with mass spectrometry was used to determine the EC levels in distillate musts and fractions produced by spontaneous or selected Saccharomyces cerevisiae strains. The aim was to verify the influence of selected strains as starters for fermentation compared with spontaneous fermentation on EC formation. The distillate fractions from these two production processes were also analysed. Our results demonstrated higher levels of EC (which surpass the limits defined by Brazilian law) in cachaças produced by spontaneous fermentation (50%) compared with the selected strains (30%); and the distillation step showed great contribution for the reduction of the compound. From must to distillate fractions we found an average decrease on EC levels of 62% using selected strains and 44% for the spontaneous fermentation. In addition, careful separation of the distillation fractions was crucial for producing high-quality and safe beverages.     

Effects of vegetable oils on gel properties of surimi gels

The objective of this study was to determine effects of vegetable oils (soybean, peanut, corn, and rap oils) on the textural, color, microstructural, sensory and rheological properties of surimi gels. As the vegetable oil concentration increased in surimi gels, breaking force of gels was decreased (P < 0.05), while expressible water and whiteness values were increased (P < 0.05). Surimi gels with peanut oil had higher breaking force values, comparing to those with other vegetable oils. Transmission electron microscope shows the similar-size droplets of peanut oil and corn oil in surimi gels. Sensory evaluation indicated that fish balls with 10 g/kg vegetable oils were accepted in term of taste, color and overall likeness by the panelists. Storage modulus (G′) and loss modulus (G″) decreased along with increasing vegetable oil concentration. Results demonstrated that vegetable oils could be used potentially to modify the qualities of surimi-based products, such as color and taste.     

低聚木糖的模拟移动床色谱分离研究

研究了用模拟移动床色谱分离高含量低聚木糖的工艺。首先通过单柱固定床实验来选择适合低聚木糖分离的固定相,比较了不同类型的离子交换树脂对低聚木糖和单糖混合液的分离度和分离效率．筛选出DIAION—UBK530Na树脂为合适的分离介质;然后运用真实移动床模型,近似确立模拟移动床色谱分离工艺的初始操作参数．在理论分离原理的指导下,优化分离条件,在阀切换时间为300s、进料流量和洗脱流量分别为3．5mL／min和5ml/min、提取液和提余液流量分别为3．8mL／min和4．7mL／min、同时循环流量控制在8．9mL／min的条件下．使分离后的低聚木糖、单糖纯度均在90％以上,收率分别达到91．55％和92．18％。     

乳酸菌β-甘露聚糖酶研究进展

β-甘露聚糖酶属于糖苷水解酶（glycoside hydrolases,GH）家族,广泛存在于植物、动物和微生物中,主要水解产物为甘露低聚糖（mannan-oligosaccharides,MOS）。微生物来源的甘露聚糖酶种类多且活性高,但大部分安全性低,其中乳酸菌（lactic acid bacteria,LAB）甘露聚糖酶具有纯化步骤少、易于提取、安全性高等优点,能够满足食品级工业生产的需求,因此在保健品、饲料、饮料生产等工业中有重要应用前景。本文介绍了天然LAB甘露聚糖酶的产酶条件、分离纯化和酶学特性,简述了近年来甘露聚糖酶的LAB重组表达及其在果汁澄清和制备益生元MOS方面的应用,为LAB甘露聚糖酶的基础研究和开发提供参考和依据。     

Study of taste-active compounds in the water-soluble extract of mature Cheddar cheese

The chemical composition of the water-soluble extracts of mature Cheddar cheese were identified, with the emphasis on understanding the interplay of compounds contributing to the savoury taste in Cheddar. The ultra-filtered water-soluble extracts of two mature Cheddar cheeses were fractionated by gel permeation chromatography (GPC). By sensory evaluation, two taste-active GPC fractions were identified from each cheese. On the basis of chemical profiling of these fractions, aqueous model tastant mixtures were prepared and sensory omission tests carried out. Glutamic acid, organic acids and mineral salts were the main tastants, whereas the other amino acids had a limited impact on taste. The characteristic umami taste was explained by a synergistic effect of glutamic acid and salts. Matching umami taste intensities were obtained from different concentrations of glutamic acid and salts. Unmasking of a bitter or sweet taste from mixtures of sub-threshold concentrations of amino acids without glutamic acids was also observed.     

金冠豆角籽粒中α-淀粉酶抑制剂的纯化及抑制动力学的研究

目的 提取金冠豆角籽粒中α -淀粉酶抑制剂（α-amylase inhibitor, α-AI）并将其进行纯化,研究其抑制类型,确定α-淀粉酶抑制剂的及抑制效果。方法 以金冠豆角籽粒为原料,通过NaCl盐溶、硫酸铵沉淀提取将α-AI进行提取,使用G50、G75葡聚糖凝胶柱进行层析,以NaCl洗脱液进行梯度洗脱,收集蛋白峰后,检测α-AI对猪胰淀粉酶的抑制活性;用Lineweaver-Burk双倒数绘图法和Michaelis-Menton方程分析酶反应动力学,通过Linerweaver-Burk作图,探究α-AI的抑制类型。结果 金冠豆角籽粒中提取的α-AI蛋白含量为1.74 mg/mL,对猪胰淀粉酶抑制率为84.20%,半抑制浓度（semi-inhibition concentrationhalf maximal inhibitory concentration, IC50 ）IC50 为6.765677±0.627 63 mg/mL、蛋白含量为1.74 mg/mL。基于酶反应动力学,利用Lineweaver-Burk双倒数绘图法和Michaelis-Menton方程分析发现,不添加抑制剂组和添加抑制剂组的α-淀粉酶的酶解速率曲线几乎相交于原点,并且酶最大反应速率（Vmax）随着抑制剂浓度的增大而减小,米氏常数（Km）不变。结论 α-AI与猪胰淀粉酶的结合呈现可逆型非竞争性抑制。     

传统发酵豆酱的微生物群落结构和游离氨基酸组成及其相关性分析

研究传统发酵豆酱产品质量的差异,通过定量描述分析法对吉林省长春、黑龙江省桦南、黑龙江省宝泉岭和黑龙江省黑河4 个地区发酵豆酱样品（分别为ChangC、HuaN、BaoQL、HeiH）进行感官评价,运用高通量测序技术和氨基酸分析技术测定其微生物群落结构和游离氨基酸组成,并探讨两者的相互关系。结果表明：BaoQL感官评价最好。不同豆酱样品的菌群组成差异较大,菌群中优势细菌和优势真菌的种类也各不相同,其中样品HuaN和HeiH的优势细菌为四联球菌（Tetragenococcus）,样品ChangC的优势细菌为乳杆菌（Lactobacillus）,样品BaoQL的优势细菌为魏斯氏菌（Weissella）;样品HuaN和HeiH的优势真菌为青霉菌（Penicillium）,样品ChangC的优势真菌为unclassified-k-Fungi,样品BaoQL的优势真菌为曲霉菌（Aspergillus）。通过对其游离氨基酸进行主成分分析和综合性评价,可得东北不同地区传统发酵豆酱游离氨基酸含量存在差异,样品BaoQL的游离氨基酸综合评分最高,样品ChangC次之,HeiH评分最低。采用偏最小二乘回归模型分析豆酱的微生物多样性和游离氨基酸组成的相关性可知,菌群的种类和丰度对游离氨基酸的组成和含量影响较大,从而影响豆酱的质量,其中对游离氨基酸含量影响较大的细菌为Weissella,真菌为毕赤酵母菌（Millerozyma）和Aspergillus。本研究揭示了豆酱中游离氨基酸与微生物群落组成之间的相关性,为豆酱产品的工业化生产提供理论依据。     

Effects of combined high-pressure and heat treatment on the textural properties of soya gels

SPI, 7S, and 11S globulin at 12% (w/v) protein concentration, at neutral pH, did not form gels when heat-treated (90 °C, 15 min) or when high pressure-treated (300–700 MPa), except for the 11S, which formed a gel when heat-treated. The combination of heat and pressure (that is heating the solutions in a water bath and then pressure-treating at room temperature or the reverse sequence), led to differences: when heat-treatment was before high-pressure treatment, only the 11S fraction formed a self-standing gel; however, when the solutions were pressurised before heat treatment, all the proteins formed self-standing gels. The textural and water-holding properties were measured on the gels formed with the three different soy proteins.