Adhesion of Listeria monocytogenes to materials commonly found in domestic kitchens

The aim of this work was to investigate the adhesion of Listeria monocytogenes ATCC 15313 to glass, granite, marble, polypropylene from a bowl (PPb), polypropylene from a cutting board (PPcb) and stainless steel (SS), which are materials commonly used in kitchens. Marble and granite were chosen because they are applied as kitchen bench covers and pavements in many countries and there are no literature reports on their behaviour in terms of microbial adhesion. The effect of surface hydrophobicity and roughness on the adhesion process was also analysed. The results showed that the highest extent of adhesion of L. monocytogenes occurred to stainless steel, followed by glass and in less extent to the other materials studied. However, it was not possible to establish a correlation between surface hydrophobicity or roughness and the extent of adhesion of L. monocytogenes . The adherence of L. monocytogenes should be dependent on other factors, like the presence of exopolymers and surface charge.     

Factors Influencing the Adhesion of Microorganisms to Surfaces

Starvation, growth phase, and carbon source influenced bacterial cell surface hydrophobicity. Both the number and kind of microorganisms that colonized metal surfaces depended on the type of metal and the presence of an imposed electrical potential. No significant differences in attachment and growth of a pure culture were observed when metal surfaces were dipped in an exogenous energy source. The chemical composition of naturally occurring adsorbed organic films on metal surfaces was shown to be independent of surface composition and polarization.     

疏水性安全壳壁面的硅表面微孔结构制备

为构建疏水性安全壳内壁面涂层以提高事故中的传热能力,以Si作为功能涂层材料,在其表面上制备了不同圆孔间距及圆孔深度的微孔阵列样品以研究微米结构对表面疏水特性的影响,并对其疏水机理进行分析。结果表明,所制备的微孔样品润湿特性均符合Cassie-Baxter模型,在本征接触角为69.5°的Si表面通过微孔结构调控可显著提高疏水特性,获得了具有140°接触角的优异疏水特性样品而未进行表面化学修饰。研究结果为设计安全壳涂层材料及其表面微结构提供了技术方案,为强化核电站非能动安全壳冷却系统传热性能提供了解决思路。     

生物形态氧化铝复合高吸油树脂的合成及性能

该文以滤纸为模板,通过浸渍-高温煅烧法制得具有生物形态的氧化铝,利用乙烯基三乙氧基硅烷(A151)对所制备样品的表面进行疏水改性。利用悬浮聚合法制备了聚甲基丙烯酸丁酯-丙烯酸丁酯-苯乙烯高吸油树脂。通过正交实验优选出最佳反应条件:分散剂用量为单体质量的5%、交联剂用量为单体质量的2%、引发剂用量为单体质量的1.5%、改性氧化铝的添加量为单体质量的4%,在该条件下制备的树脂的吸收倍率较原树脂有了明显的提高,而且复合树脂能够反复使用多次。对改性前后的氧化物进行红外光谱(IR)、透射电镜(TEM)、扫描电镜(SEM)以及动态疏水性分析,并对复合高吸油树脂进行扫描电镜(SEM)和热重(TG-DTA)分析。     

The characteristic curvature (Cc) definition and its use in assessing Cc for single ionic surfactants

The hydrophilic–lipophilic-difference (HLD) is a set of empirical equations that correlate the formulation conditions at phase inversion (HLD = 0). Based on partition studies for nonionic surfactants, the HLD can be interpreted as a normalized chemical potential difference between the surfactant dissolved in water and oil. The net-average curvature (NAC) model extrapolates this interpretation into a curvature form that has been used to fit and predict the phase behavior of surfactant-oil–water (SOW) systems. The curvature interpretation led to renaming the HLD surfactant parameter, sigma (σ), as the characteristic curvature (Cc). This work tests the validity of the curvature interpretation of the HLD, and the Cc concept, for single ionic surfactants and the use of this concept as a method to assess the Cc without the use of reference surfactants or alcohols. To this end, the net curvature of six anionic and two cationic surfactants was evaluated from solubilization data at the characteristic condition of 25°C, no added cosolvent, in the presence of an oil mixture with equivalent alkane carbon number (EACN) of zero, and as a function of salinity. These studies showed that the original HLD equation for ionic surfactant could not be interpreted as chemical potential or curvature because a salinity prefactor (coefficient) “bi” was missing. The revised equation, HLD_bi = bi∙ln(S)-k_bi∙EACN+Cc_bi -a_Tbi∙(T-25°C), could now be interpreted as a curvature expression, and it was demonstrated that Cc could be obtained from curvature using the expression Cc = Cc_bi/bi. This single surfactant method produces uncertainties that, for most surfactants, ranged from 0.2 to 1 Cc units, similar to the uncertainty obtained with the conventional method of Cc determination using mixtures of test and reference surfactants.     

3种淀粉对鸡肉糜盐溶蛋白特性影响及其配方研究

为获得鸡肉蛋白较好的凝胶特性,从而改善其肉糜的加工品质,探讨玉米淀粉、马铃薯淀粉和磷酸酯淀粉3种常用淀粉与鸡肉盐溶蛋白相互作用对鸡肉糜加工基本特性的影响。以盐溶蛋白析出质量浓度、活性自由巯基含量和相对疏水性为指标,分别研究单因素条件下3种淀粉对鸡肉盐溶蛋白特性的影响,并通过二次通用旋转试验筛选出在5%淀粉添加总量条件下3种淀粉在鸡肉糜中的最佳组合配方。单因素试验表明:所选3种淀粉均对鸡肉盐溶蛋白特性有着复杂影响。3种淀粉最佳配方为:玉米淀粉1.6%、马铃薯1.6%、磷酸酯淀粉1.8%,此时鸡肉糜中盐溶蛋白基本特性参量指标预计为:盐溶蛋白质量浓度24.3mg/mL,活性自由巯基含量0.004μmol/mg,相对疏水性值22.86。     

Use of macroporous adsorption resin for simultaneous desalting and debittering of whey protein hydrolysates

Whey protein isolate (WPI) was hydrolysed to whey protein hydrolysates (WPH) of degree of hydrolysis equal to 15% using Protease N ‘Amano’ G (IUB 3.4.24.28) in a batch reactor at 55 °C and pH 7.0 according to the pH‐stat procedure. Ash was removed by adsorbing WPH onto macroporous adsorption resins (MAR). Following rinsing with deionised water, desorption was achieved by washing with 20%, 40% and 75% alcohol (v v^?1) to obtain the three fractions HS20, HS40 and HS75. Ash reduced from 15.71% (WPH) to 4.38% (HS20), 2.02% (HS40) and 2.38% (HS75). Similarly, the protein content was enriched from a low of 64.89% (WPH) to 94.74% (HS20), 95.32% (HS40) and 92.00% (HS75). The fractions were analysed for surface hydrophobicity (SH_o), angiotensin‐I converting enzyme (ACE) inhibition, emulsifying activity index, total amino acids composition and molecular weight distribution. Fraction HS75 was objectionably bitter, showed superior ACE inhibition (lowest IC₅₀), had the highest content of hydrophobic and essential amino acids and contained about 71% of <600 Da with no fractions exceeding 4142 Da. Desorption with alcohol weakened the hydrophobic interaction forces between the peptides and resins and hence eluted the peptides, with the bitter HS75 being extracted.     

Flocculation,cell surface hydrophobicity and 3‐OH oxylipins in the SMA strain of Saccharomyces pastorianus

Three‐hydroxy‐oxylipins (3‐OH oxylipins) have been previously detected in brewing yeast production strains at flocculation onset. In this work, the SMA strain of Saccharomyces pastorianus was characterized during growth in a miniature fermentation assay by measuring flocculation and cell surface hydrophobicity (CSH). Proportions of 3‐OH oxylipin were also measured concurrently during growth in the miniature fermentation assay and a defined 3‐OH oxylipin extraction protocol using ethyl acetate is presented along with a novel derivatization and gas chromatography–mass spectrometry (GC‐MS) detection approach. When the SMA strain was grown in the assay, near maximal CSH and flocculation levels were achieved by a 36 h fermentation time. Under the same culture conditions, the oxylipin 3‐OH decanoic acid (3‐OH 10:0) was identified. This oxylipin could not be detected early in the fermentation, but elevated relative levels of 3‐OH 10:0 were reached by 36 h, coinciding with increased CSH levels. It was previously presumed that the formation of 3‐OH oxylipins at flocculation onset might increase the CSH. However, results from this study suggest that 3‐OH 10:0 may not contribute to cell wall hydrophobicity. The flocculation behaviour of the SMA strain was also monitored in the presence of 3‐OH 10:0, but exposure to this oxylipin did not impact the sedimentation of this yeast, suggesting that 3‐OH oxylipins may not act as mediators of quorum sensing in this strain. Copyright © 2015 The Institute of Brewing & Distilling     

采用图像分析与神经网络识别绝缘子憎水性

为了快捷准确的识别复合绝缘子的憎水性等级,提出了基于图像分析与神经网络的绝缘子憎水性识别方法.试验获取各个憎水性等级的绝缘子图像,对图像进行直方图均衡增强、自适应中值滤波处理后,利用二维Otsu阈值法对图像进行分割;然后,提取4个与绝缘子憎水性相关的4个特征量,以这4个特征量作为输入向量,以相应的憎水性等级作为输出向量,通过训练得到优化的BP(back propagation)神经网络识别模型,并用于绝缘子憎水性等级的识别.试验结果表明该方法能够准确识别绝缘子的憎水性等级,总识别率超过了90％,准确度达到了实际应用的要求,为在线检测绝缘子憎水性奠定了基础.     

Effect of Hydrostatic Pressure on Molecular Conformation of Tilapia (Orechromis niloticus) Myosin

ABSTRACT: Change in tilapia myosin molecular conformation due to pressurization at 50 to 200 MPa for 0 to 60 min was investigated. After a 50-MPa treatment, tilapia myosins slightly decreased their total sulfhydryl contents and exposed their hydrophobic residues. Experimental results indicated that 100- and 150-MPa treatments caused an apparent unfolding of myosins and a 1-fold increase of their surface hydrophobicity ( S _o). Myosins mainly formed intermolecular disulfide bonds with pressures of 100 to 200 MPa. In addition, increasing pressures altered the myosin conformation and decreased its Ca-ATPase activity. Myosin apparently unfolded and formed disulfide bonds and hydrophobic interactions with pressurizing at 150 MPa.