Absence of allergenic residues in experimental and commercial wines fined with caseinates

The possible presence of allergenic residues in wines treated with one of the potassium caseinates used as fining agents has been investigated.     

Suspension stability and size distribution of particles in reconstituted,commercial calcium caseinates

Four commercial calcium caseinates were reconstituted in water and various properties of the particles or aggregates were determined. Particle size distribution was determined with a Malvern Mastersizer. All the dispersions exhibited bimodal particle size distributions with modes at about 0.4 and 10 μm. The particle size distributions changed quite rapidly for the first 2 h after reconstitution and then changed more slowly for up to 6 h. The mode of the first peak did not change significantly during this time, but the mode of the second peak decreased. It appeared that the larger particles were either dissociating into smaller particles or dissolving with time. The sample with the lowest suspension stability had the largest particles. Sediment formed by centrifuging the dispersions at 700 g had a moisture content of about 77% and was slightly enriched in ash compared to the original dispersion. The density of the hydrated sediment was calculated from the sediment composition to be about 1073 kg m⁻³. This appears to be much higher than the density of the sedimenting particles as estimated from Stokes law.     

Structure and mechanical properties of sodium and calcium caseinate edible active films with carvacrol

Edible active films based on sodium caseinate (SC) and calcium caseinate (CC) plasticized with glycerol (G) at three different concentrations and carvacrol (CRV) as active agent were prepared by solvent casting. Transparent films were obtained and their surfaces were analysed by optical microscopy and scanning electron microscopy (SEM). The influence of the addition of three different plasticizer concentrations was studied by determining tensile properties, while Fourier transformed infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were used to evaluate the structural and thermal behavior of such films. The addition of glycerol resulted in a reduction in the elastic modulus and tensile strength, while some increase in the elongation at break was observed. In general terms, SC films showed flexibility higher than the corresponding CC counterparts. In addition, the presence of carvacrol caused further improvements in ductile properties suggesting the presence of stronger interactions between the protein matrix and glycerol, as it was also observed in thermal degradation studies. FTIR spectra of all films showed the characteristic bands and peaks corresponding to proteins as well as to primary and secondary alcohols. In summary, the best results regarding mechanical and structural properties for caseinates-based films containing carvacrol were found for the formulations with high glycerol concentrations.     

Effect of repeated frying on the viscosity, density and dynamic interfacial tension of palm and olive oil

The effect of deep-fat frying on the viscosity, density and dynamic interfacial tension (against air and water) of palm oil and olive oil was investigated. Repeated frying (up to 40 batches) at two different potato-to-oil ratios (1/7, 1/35 kg_potatoes/L_oil) was examined. Results were compared to those from simple heating the oils at the same temperatures. Viscosity increased during repeated frying for both oils. However, only palm oil viscosity was sensitive to potato-to-oil ratio. Due to the novelty of dynamic interfacial characterization of such systems a discussion was made about the appropriate timescales and deformation types for interfacial measurements. Significant effects of repeated frying on the dynamic interfacial tension at the oil/water interface were observed. Contrarily, changes in density were not significant. Results were assessed with respect to the evolving chemical profile of the oils determined in previous works. Possible implications of the determined properties on the frying process were discussed.     

新型表面活性剂的表面张力和电导率性能研究

合成了三种孪连型阳离子季铵盐表面活性剂16-4-16,2Br-1、14-4-14,2Br-1、18-2-18,2Br-1,对三者的性能进行评定,分别通过表面张力和电导率测得临界胶束浓度(CMC)、表面活性剂在气-液界面的吸附量、单个分子的面积和胶束电离度α。结果表明:首先,相对于单头基单尾链的表面活性剂,三种孪连表面活性剂的表面活性更强,CMC值更低;其次,三种表面活性剂都有其各自的特性,16-4-16,2Br-1的粘弹性能较好,而14-4-14,2Br-1、18-2-18,2Br-1表面张力很低。实验表明,通过调节孪连表面活性剂联结基和疏水链的长度会对产品的性能有很大的影响。     

非理想多元混合表面活性剂体系的混合吸附和表面张力方程

应用拟二元体系方法将非理想二元混合表面活性剂体系的吸附理论推广到非理想三元体系并建立了三元体系的表面张力方程．由此对含有３个组分的多元体系,根据各单一表面活性剂体系的γ－ ｌｇＣ曲线和所有两组分间的相互作用参数βｓｉｊ（ｉ＝ １．２．３？ｊ＝ １．２．３？ｉ≠ｊ ）即可预测达到给定表面张力下降所需的不同体相组成的混合体系的浓度和混合吸附单层的组成,或者应用所建表面张力方程预测混合物溶液的表面张力．应用于ＡＥＳ／ＡＥＯ９／ＤＰＣｌ＋ ０．１ ｍ ｏｌ／Ｌ ＮａＣｌ非理想三元混合体系,理论预测结果与实验结果一致．     

利用固液润湿效应研究液体表面张力

实验中发现不同的液体与不同的金属丝的表面相不同 .插入液体里的金属细丝拉出液面时 ,由于液体的表面张力的作用 ,将带动金属细丝下的液体拉伸一定高度而断裂 .分析了上述现象的机理 ,可应用于液体表面张力系数的测定     

蛋白质溶液表面张力及其与功能性质的关系

为了探讨蛋白质溶液表面张力的变化规律，本文利用表面张力计和食品流变学方法系统地研究了蛋白质溶液表面张力随液滴停留时间的变化及其与功能性质的关系。结果表明：高浓度时，液滴停留时间与表面张力的变化遵循下列一次方程In[（θt-θe）/（θw-θe）]=-kt。对同一蛋白质来说，k值随浓度的增加而增大。蛋白质起泡力与k值呈极显著的线性关系，泡沫稳定性与k值呈正相关。蛋白质的乳化性低浓度时与表面张力呈正相关；高浓度时，乳化性与k值呈正相关。     

奶牛初乳的表面张力研究

初乳的表面张力较常乳低１－１０ｍＮ／ｍ＾－１，在２０－６０℃的区间内初乳的表面张力均随温度上升而呈下降趋势，其值主要同初乳的蛋白含量决定，脂肪伉不是决定表面张力的主因。     

介绍一种简单易行的测定表面张力的仪器

本文介绍了一种简单易行的由移液管改制的测定表面张力的仪器及其操作原理和使用方法。     

Surface tension of Phaseolus vulgaris and coccineus proteins and effect of polysaccharides on their foaming properties

The surface tension of protein isolates from common bean (Phaseolus vulgaris L.) and scarlet runner bean (Phaseolus coccineus L.), prepared by isoelectric precipitation and ultrafiltration was evaluated, with respect to protein concentration (0.001–0.1% w/v) and pH (pH 4.5, 5.5, 7.0 and 8.0). Surface tension was most reduced, and with a higher rate of reduction at higher protein concentration and at pH 8.0. Foams (1, 2% w/v protein), at the same pH values, with and without the addition of polysaccharides, were studied. The proteins’ foaming behaviour was related to their adsorption behaviour. Arabic gum, locust bean gum (0.1% and 0.25% w/v), xanthan gum and a xanthan/locust bean gum mixture (0.1% w/v) had a positive effect on foam creation. All polysaccharides increased foam stability, probably due to the viscosity increase and to the creation of a network, which prevents the air droplets from coalescence. Isolates from P. coccineus and isolates obtained by ultrafiltration seemed to exhibit better foaming properties.     

从溶液表面张力谈茧层渗润性能的改善

从渗透及前处理的溶液性质,探讨其对茧层渗润性的影响。通过有关理论研究,论述了提高浸润性能、改变溶液性质、降低表面张力的方法,以及表面活性剂的选择与用量。     

增稠剂和乳化剂对豆浆稳定性的影响

为增加豆浆的稳定性,采用测定豆浆稳定系数、表面张力及进行感官评分的方法筛选适合用于豆浆样品的增稠剂和乳化剂,确定了最适宜的豆浆增稠剂和乳化剂的种类及其用量。经过黄原胶、刺槐豆胶、卡拉胶、结冷胶和海藻酸钠的单因素实验,黄原胶和刺槐豆胶的复配实验及黄原胶、刺槐豆胶和乳化剂(单硬脂酸甘油酯和蔗糖脂肪酸酯)的正交实验得出以下结果:黄原胶和刺槐豆胶对增加豆浆稳定性有着较好的效果,当它们的质量浓度分别为0.2g/L时,其稳定系数分别为0.737、0.742。单硬脂酸甘油酯和蔗糖脂肪酸酯复配后HLB=8、质量浓度为2g/L时,豆浆样品的稳定性最好,表面张力为41.7mN/m。当黄原胶、刺槐豆胶、乳化剂质量浓度(单硬脂酸甘油酯质量∶蔗糖脂肪酸酯质量=7∶4)分别为0.14、0.14、2g/L时豆浆的稳定性最好,此时豆浆样品的稳定系数为0.879,表面张力为41.6mN/m,感官评分为96。     

Influence of semi-solid fluid’s surface tension and rheological properties on the residues at packaging materials

Residues of food are unwanted in food processing and food packaging. Therefore different properties of high viscous food and their relevance to adhesion phenomena at packaging surfaces are investigated herein. The results may be utilised to reduce the amount of sticking content.In order to quantify the amount of remaining material a method of evaluation was designed using polysaccharides solutions and mixtures of highly viscous oils as model products. The surfaces tension and rheological properties were analyzed. The work of adhesion of each product-surface system was calculated from the respective contact angle data.It was found that the viscosity has a great influence on the amount of residues. For Newtonian liquids the influence is linear. For viscoelastic liquids there are other effects that cause fewer residues when the viscosity is increased. Furthermore, it seems that fewer residues remain when the dispersive part of the surface tension of the liquid is high. Aside from this the work of adhesion is a good measure to predict the amount of residue.     

Effect of gum arabic on the surface tension and surface dilational rheology of trisiloxane surfactant

The surface tension and surface dilational properties of trisiloxane surfactant silwet408, gum arabic, and their mixed solutions are reported. The dilational rheological properties are measured by means of oscillating drop method. The influences of dilational frequency, bulk concentration and aging time on dilational rheology properties have been investigated. The adsorption films of silwet408 behave elastic in nature at low bulk concentration. With increasing concentration, the dilational modulus becomes more frequency dependent and reaches a maximum value. The addition of 1 wt% gum arabic has no remarkable influence on the silwet408 films since the adsorption ability of silwet408 is much better than that of gum arabic. However, the maximum of dilational modulus and dilational elasticity are shifted toward a higher concentration, which has been correlated with the decreased molecular exchange in the presence of 1 wt% gum arabic.     

烷基糖苷水溶液的表面活性以及电解质的影响

烷基糖苷APGs作为新一代绿色表面活性剂,以其优异的表面特性在各个领域的应用开发受到了广泛的关注。文章深入研究了不同链长的烷基糖苷水溶液的表面张力、胶束化行为以及电解质的加入对其的影响。结果表明,APGs溶液的CMC主要取决于其分子疏水端的结构。随着疏水链的增长,APGs溶液的CMC随之减小。相对离子型表面活性剂而言,硫酸钠的加入对溶液的影响较小,主要是通过对疏水链的盐析作用来实现的。在强碱体系下,APGs分子亲水端部分去质子化使得所形成的胶束带负电性,从而导致氢氧化钠的盐析效应相对较弱。     

Measurement,prediction and correlation of density,viscosity, surface tension and ultrasonic velocity of different honey types at different temperatures

The aim of this study is to investigate the influence of temperature (20, 25, 30, 35, 40, 45 and 50 °C) and concentration on the evolution of different physical properties (density, viscosity, ultrasonic velocity and surface tension) of honeys. Temperature influences negatively all the physical properties of honey. A good correlation between density, viscosity, ultrasonic velocity and surface tension using linear and polynomial equations was observed. Also a good correlation between density, ultrasonic velocity and surface tension for all the honey samples (R² = 0.954) was obtained. The correlation between surface tension and viscosity was made using the Pelofsky model and an exponential model; the latter one describes better the correlation between surface tension and viscosity.     

槐糖脂表面特性和抗氧化活性的初步研究

对槐糖脂的表面特性和抗氧化活性进行了初步研究,采用最大气泡法测其最小表面张力,同时分析不同条件下表面张力的稳定性,通过表面张力浓度曲线求得其临界胶束浓度,利用超声乳化法分析槐糖脂的乳化活性表征表面特性。槐糖脂的体外抗氧化能力则通过DPPH自由基清除实验进行分析。结果表明:葡萄糖/油酸和豆油发酵的槐糖脂的最小表面张力分别为40、38mN/m,临界胶束浓度分别为60、70mg/L。槐糖脂在高温和高盐离子浓度下均表现出稳定的表面活性,在强酸、强碱条件下稳定性较差。乳化活性分析,两种槐糖脂中对于豆油、芝麻油和石蜡的乳化率大于80%。两种槐糖脂均具有体外抗氧化活性,以豆油为底物发酵的槐糖脂比以葡萄糖/油酸为底物发酵的槐糖脂具有更好的体外抗氧化活性。     

Rudin改良法测定啤酒泡持性条件的优化

以Rudin改良法测定的啤酒泡持性为评价指标,在单因素和中心旋转组合实验设计结果的基础上,通过响应曲面法优化Rudin改良法测定啤酒泡持性的条件。结果显示:3个因素对泡持值测定的影响依次为气体总阀出口压力>CO2流量>待测样品预处理温度。分析结果显示,Rudin改良法测定啤酒泡持性的最优条件为气体总阀出口压力取0.3MPa,CO2流量取340mL/min,待测样品预处理温度取20℃,泡持值为110.813s,与预测值111.363s的相对误差为0.49%。回归方程的预测值和实验值差异不显著,所得回归模型拟合情况良好,可应用于实际操作。