单甘酯对酪蛋白乳浊液稳定性的影响

在酪蛋白乳浊液体系中研究了单甘酯用量对乳浊液界面乳化剂浓度、液相蛋白浓度、粒度分布、脂肪部分聚结率及离心乳析率的影响,探讨了单甘酯对酪蛋白乳浊液稳定性影响的机理。结果表明:随着单甘酯用量的增加,单甘酯在界面膜上的竞争吸附作用增强,界面单甘酯浓度和液相蛋白浓度均逐渐增高;表面积平均直径D[3,2]、体积平均直径D[4,3]、脂肪部分聚结率和离心乳析率均先减小后增大,单甘酯用量为0.60%时达到最小值,乳浊液稳定性最好。     

单甘酯对酪蛋白乳浊液稳定性的影响

在酪蛋白乳浊液体系中研究了单甘酯用量对乳浊液界面乳化剂浓度、液相蛋白浓度、粒度分布、脂肪部分聚结率及离心乳析率的影响,探讨了单甘酯对酪蛋白乳浊液稳定性影响的机理。结果表明,随着单甘酯用量的增加,单甘酯在界面膜上的竞争吸附作用增强,界面单甘酯浓度和液相蛋白浓度均逐渐增高;表面积平均直径D(3,2)、体积平均直径D(4,3)、脂肪部分聚结率和离心乳析率均呈现先减小后增大趋势,单甘酯用量为0.6%时达到最小值,乳浊液稳定性最好。     

乳化剂用量对搅打稀奶油搅打性能和品质的影响机理研究

研究了乳化剂用量对搅打稀奶油的乳浊液粒度分布、脂肪球部分聚结、液相蛋白浓度、感官品质和泡沫稳定性的影响。研究结果表明:乳浊液冷却及解冻后脂肪球粒径随乳化剂用量增加而减小,随着乳化剂用量增加,脂肪部分聚结速度和液相蛋白质浓度增加速度加快,搅打起泡率和感官品质以乳化剂用量为0.60%时最好,搅打稀奶油稳定时间随乳化剂用量增加呈先增加后下降趋势,当乳化剂用量为0.60%时,稳定时间达到最大2.4h。综合考虑,当乳化剂HLB值为7,乳化剂用量为0.60%时,搅打稀奶油搅打性能和品质最佳。     

大豆蛋白与酪蛋白比例对搅打稀奶油稳定性影响的研究

研究了大豆蛋白与酪蛋白不同配比对搅打稀奶油乳浊液的表观粘度及搅打过程中的液相蛋白浓度、脂肪部分聚结、搅打起泡率的变化和泡沫稳定性的影响,并在此基础上探讨了其作用机理。结果表明:大豆蛋白比例的增大能增加界面膜的粘弹性,抑制脂肪球的部分聚结,提高泡沫结构的稳定性,当大豆蛋白与酪蛋白比例为4∶1时,搅打稀奶油可以获得最佳的稳定性。     

乳化剂的复配比例和用量对花生乳稳定性影响的研究

研究了乳化剂中蔗糖酯与单甘酯的复配比例(1:2～2:1)和用量(0.03%～0.07%)对花生乳的粒度分布,离心乳析率、离心沉淀率和储存稳定性的影响,研究结果表明:随着乳化剂中蔗糖酯(以单甘酯计)的比例上升,花生乳的粒径、离心乳析率和离心沉淀率均呈先减小后增大趋势,当蔗糖酯和单甘酯的复配比例为2:3时储存稳定性最好;当乳化剂用量低于0.05%时,随其用量的增加,花生乳的粒径、离心乳析率和离心沉淀率均呈下降趋势,储存稳定性逐渐提高,当乳化剂用量高于0.05%时,花生乳的粒径、离心乳析率,离心沉淀率和储存稳定性变化不明显;综合考虑,当乳化剂中蔗糖酯和单甘酯的复配比例为2:3,用量为0.05%时,花生乳的稳定性最好.     

油脂用量对搅打稀奶油的搅打性能和品质的影响

研究了油脂用量对搅打稀奶油的粒度分布、脂肪部分聚结、液相蛋白质浓度、搅打起泡率、质构特性、感官品质和稳定时间的影响。研究表明:随着油脂用量增加,冷却后乳浊液脂肪球粒径增大;搅打过程中脂肪部分聚结速度和脂肪球粒径d4,3均随油脂用量增加而增大,且脂肪部分聚结率与脂肪球粒径d4,3有很好的相关性;液相蛋白质浓度和搅打起泡率降低;搅打稀奶油的质构特性值增加;稳定时间呈先增后减趋势,当油脂用量为23%时,搅打稀奶油的稳定时间最长达到2.7h;搅打稀奶油的感官品质以油脂用量为20%最好,综合考虑,油脂最佳用量范围是20%-23%。     

蛋白质用量对黄油基淡奶油搅打前乳液性质及搅打性能的影响

以黄油为油相制备淡奶油,研究蛋白质用量(1.0%～3.0%)对黄油基淡奶油搅打前乳液性质及搅打性能的影响。研究表明:蛋白质用量为1.0%～2.5%时,随蛋白质用量的增加,搅打前乳液的界面蛋白浓度明显增加,脂肪部分聚结率降低,脂肪球粒径减小,粒度分布曲线变窄,表观黏度升高,乳液的稳定性提高;蛋白质用量由2.5%增加至3.0%时,脂肪部分聚结率增加,脂肪球粒径增大,乳液的稳定性降低。乳液在200 s的搅打过程中,随搅打时间的延长,脂肪部分聚结率不断增加,平均粒径呈现先减小后增大的趋势,搅打起泡率则先升高后降低。蛋白质用量为1.0%～1.5%时,在搅打过程中脂肪部分聚结率、平均粒径、搅打起泡率均快速增加,易出现搅打过度现象,且泡沫稳定性差。蛋白质用量为2.0%～2.5%时,脂肪部分聚结率、平均粒径、搅打起泡率则缓慢增加,而泡沫稳定性较好。蛋白质用量增加至3.0%时,尽管泡沫稳定性较好,但搅打200 s后的脂肪部分聚结率仅有26.45%。因此,将黄油基淡奶油的蛋白质用量控制在2.0%～2.5%范围内较适宜。     

黄原胶对蔗糖酯乳浊液流变特性及稳定性的影响

本文研究了黄原胶浓度对蔗糖酯溶液水力学直径DH、ζ-电势及乳浊液粒径、ζ-电势、显微结构、粘度、模量和乳析分层等指标的影响,在此基础上探讨了黄原胶对蔗糖酯乳浊液流变特性及稳定性的影响。结果表明:随着黄原胶浓度升高,蔗糖酯-黄原胶复合溶液的DH值逐渐增大,ζ-电势逐渐降低。乳浊液的粒径先增大后减小,ζ-电势没有显著的变化(p0.05),乳浊液的粘度和模量逐渐增大。低黄原胶浓度(0~0.01 wt%)条件下,乳浊液仅出现油析分层现象;黄原胶浓度为0.05 wt%时,由于排斥絮凝作用增强,导致乳浊液的水析及油析分层最严重;随着黄原胶浓度进一步升高,由于弱凝胶网络结构的形成,一定程度提高了乳浊液的稳定性;且黄原胶浓度高于0.15 wt%时,乳浊液仅出现水析分层现象。     

NaCl浓度对蔗糖酯黄原胶乳浊液稳定性的影响

研究NaCl浓度对蔗糖酯-黄原胶溶液的水力学直径DH、ζ-电势和界面张力及乳浊液的粒径d4,3、ζ-电势、粘度和稳定性的影响。在此基础上,探讨蔗糖酯-黄原胶相互作用与乳浊液稳定性之间的联系。结果表明:随着NaCl浓度增加,由于静电屏蔽作用,蔗糖酯-黄原胶溶液的DH值、ζ-电势和界面张力均增大,导致乳浊液ζ-电势和d4,3也逐渐增大。NaCl浓度达到0.1mol/L时,由于蔗糖酯-黄原胶疏水作用增强,形成蔗糖酯-黄原胶复合物,提高液滴的空间位阻作用,使得复合乳浊液稳定性高于蔗糖酯乳浊液稳定性。     

瓜尔豆胶对大豆分离蛋白乳浊液稳定性的影响

研究了不同pH值条件下瓜尔豆胶对大豆分离蛋白乳浊液乳析稳定性和絮凝稳定性的影响。研究结果表明 ,在瓜尔豆胶浓度低于 0 0 4%时 ,随着瓜尔豆胶浓度的增加 ,乳浊液的稳定性逐渐增加。当多糖浓度高于 0 0 4%时 ,液滴发生排斥絮凝 ,体系的稳定性急剧下降 ,更高浓度的瓜尔豆胶因与乳浊液液滴间的热力学不相容性而导致体系发生各向同性和各向异性相分离。     

Production and stabilization of a flaxseed oil multi-layer emulsion containing sodium caseinate and pectin

The purpose of this research is the evaluation of a flaxseed oil-in-water emulsion, stabilized by a multi-layer structure consisting of sodium caseinate (Na-caseinate) and pectin to provide a basis for the combination of these materials for future studies. In the first step, the o/w emulsion (10 g oil, 90 g aqueous phase, and a pH 6.8) with varying concentration of Na-caseinate was investigated. Second, the pectin solution (0.05–1.5 g/100 g solution) was added to the primary emulsions and the pH was adjusted to 3.0. The emulsions were characterized by mean particle size (dynamic light scattering and static light scattering techniques), ζ-potential, turbidity value, creaming index, and the visualization of the microstructure. A clear separation of the oil phase at low protein contents and destabilizing by depletion flocculation at high protein content were observed. Extensive droplet flocculation and coalescence were determined until the pectin concentration reached 0.5 g/100 g solution for the secondary emulsion. After 7 days of storage, a 1.5 g/100 g solution pectin content had good stability with a relatively small size distribution, high turbidity value, and no cream phase separation.     

Interaction between Emulsion Droplets and Escherichia coli Cells

ABSTRACT Oil‐in‐water emulsions (20% n‐hexadecane, v/v) were stabilized by dodecyltrimethylammonium bromide (DTAB), Tween 20, or sodium dodecyl sulfate (SDS). Particle size distribution and creaming stability were measured before and after adding Escherichia coli cells to emulsions. Both E. coli strains promoted droplet flocculation, coalescence, and creaming in DTAB emulsions, although JM109 cells (surface charge = ‐35 mV) caused faster creaming than E21 cells (surface charge = ‐5 mV). Addition of bacterial cells to SDS emulsions promoted some flocculation and coalescence, but creaming stability was unaffected. Droplet aggregation and accelerated creaming were not observed in emulsions prepared with Tween 20. Surface charges of bacterial cells and emulsion droplets played a key role in emulsion stability.     

Influence of xanthan gum on the formation and stability of sodium caseinate oil-in-water emulsions

Studies have been made of the changes in droplet sizes, surface coverage and creaming stability of emulsions formed with 30% (w/w) soya oil, and aqueous solution containing 1 or 3% (w/w) sodium caseinate and varying concentrations of xanthan gum. Addition of xanthan prior to homogenization had no significant effect on average emulsion droplet size and surface protein concentration in all emulsions studied. However, addition of low levels of xanthan (≤0.2 wt%) caused flocculation of droplets that resulted in a large decrease in creaming stability and visual phase separation. At higher xanthan concentrations, the creaming stability improved, apparently due to the formation of network of flocculated droplets. It was found that emulsions formed with 3% sodium caseinate in the absence of xanthan showed extensive flocculation that resulted in very low creaming stability. The presence of xanthan in these emulsions increased the creaming stability, although the emulsion droplets were still flocculated. It appears that creaming stability of emulsions made with mixtures of sodium caseinate and xanthan was more closely related to the structure and rheology of the emulsion itself rather than to the rheology of the aqueous phase.     

Stability of Whey Protein Concentrate/Sunflower Oil Emulsions as Affected by Sucrose and Xanthan Gum

The effect of the addition of sucrose and xanthan gum, protein concentration, and processing method on the stability and destabilization mechanism type of emulsions formulated with two commercial whey protein concentrate powders was described and quantified following system changes with a Turbiscan TMA 2000, a light scattering equipment and a confocal laser scanning microscope. Two different processing methods that gave particle sizes with different orders of magnitude were compared: homogenization by ULTRA-TURRAX (UT) and by ultrasound (US). The addition of sucrose to the aqueous phase of emulsions significantly diminished volume-weighted mean diameter (D _4,3) and improved stability. When the aqueous phase contained xanthan gum, the main destabilization mechanism for UT emulsions changed from creaming to flocculation. For US emulsions, although some aggregation was detected by confocal laser scanning microscopy, it was not great enough to modify the backscattering average (BS_av) in the middle zone of the tube (20–50 mm). At low protein concentrations, the profiles corresponded to destabilization of small aggregates. In those conditions, creaming was markedly enhanced as evident from creaming rate values. Independently of aqueous phase composition, US emulsions stabilized by protein concentrations higher than 5 wt% were stable, indicating that whey proteins were good emulsion stabilizers at pH close to 7. This study shows the relevance of protein type on stability and describes for the first time a behavior for whey proteins different from the one reported for caseins in literature.     

Impact of cream washing on fat globules and milk fat globule membrane proteins

Milk proteins, contained within the aqueous phase surrounding fat globules, should be removed before analysis of the composition of the native milk fat globule membrane (MFGM). The effect of the conditions applied during washing of cream on MFGM integrity has not been fully studied, and factors potentially effecting a modification of MFGM structure have not been systematically assessed so far. In this study, a cream separator was used to investigate the impact of cream washing on milk fat globule stability and the corresponding loss of MFGM proteins. Flow velocity, fat content, and type of washing solution were varied. Particle size measurements and protein analyses were carried out after each washing step to determine fat globule coalescence, removal of skim milk proteins, and efficiency of MFGM isolation. Significant differences in fat globule stability and protein amount in the MFGM isolates were measured using different washing conditions.     

天然和热处理大豆蛋白稳定乳液的性质研究

热处理(901、20℃)修饰的大豆分离蛋白用于制备水包油(O/W)乳液,并对天然和热处理蛋白乳液的粒径、微结构、絮凝率和分层稳定性进行表征。热处理蛋白的水力学半径随蛋白浓度和加热温度的增加而增加,证实了可溶性聚集体的产生。乳液粒径和分层稳定性受离子强度、聚集体粒径影响。低离子强度下(0 mmol/L),与天然蛋白相比,热处理蛋白乳液粒径较大,20 d放置后未发生分层。离子强度的增加(100mmol/L)导致天然蛋白乳液粒径明显增大;而热处理蛋白乳液则表现出较高耐盐性,体现在更小的粒径、絮凝率和分层指数。与90℃热处理相比1,20℃热处理减小了乳液液滴的粒径和絮凝。     

Moisture and sucrose transfer in fractionated palm kernel (PKO) based films immersed in liquid solutions

The effects of addition of sucrose, lecithin, and cellulose on unsteady state diffusivity and steady state permeability of moisture through fractionated palm kernel oil (PKO)-based films were studied under liquid-induced moisture migration at a water activity gradient of 1.0 and at a temperature of 25 °C. Addition of sucrose, cellulose, and lecithin into the fat films decreased the diffusivity of moisture, but increased the permeability of moisture due to the high moisture sorption capacity of these hydrophilic components.The effect of sucrose concentration and the presence of sugar ester in the aqueous phase on the diffusivity and permeability of moisture through the fat-based film were also studied. For pure PKO films, sucrose concentration of the aqueous phase and presence of sugar ester in the aqueous phase had no effect on the diffusivity and permeability. For fat-based films containing sucrose, with increasing sucrose concentration of the aqueous phase, the diffusivity increased but the permeability decreased. Presence of sugar ester at 0.3% in the aqueous phase significantly increased permeability of the fat-based films containing sucrose.The mass transfer coefficient for sucrose leaching from the fat based films into the aqueous phase increased with sucrose content in the film. The rate of sucrose leaching out from the fat film into 0.3% sugar ester solution was higher than that into pure water. The diffusivity of sucrose in the fat film leaching out into the aqueous phase increased with sucrose content in the fat films.