Effect of phenolic antioxidants on the dispersion state and chemical stability of olive oil O/W emulsions

The effect of gallic acid, catechin and quercetin on physical and chemical stability of olive oil-in-water emulsions was investigated. These molecules, characterised by different polarity and antioxidant activity, showed different interface activity and efficiency in delaying lipid oxidation. Gallic acid contributed positively to stabilise the colloidal properties of the systems toward physical instability whilst showed a low activity towards secondary oxidation. Catechin showed an interfacial localisation which was reflected in the enhancement of primary oxidation and in the inhibition of secondary oxidation. Quercetin poorly partitioned in the aqueous phase and was proven not to slow down the bimolecular phase of auto-oxidation.Results confirmed that polarity is not the only parameter to determine efficiency of antioxidants in emulsions but other variables, such as its antioxidant activity in terms of capacity and rapidity in donating an hydrogen atom, can affect its protective role towards lipids auto-oxidation in emulsions.     

Effects of flavonoids on physical and oxidative stability of soybean oil O/W emulsions

Flavonoids have attracted attention due to pharmacological and antioxidative activities. The effects of flavonoids on the physical and oxidative stabilities of lecithin emulsified soybean oil-in-water (O/W) emulsions were investigated at 25°C during 29 days of storage. Addition of 100 ppm hesperidin, hesperitin, rutin, or quercetin improved the physical stability of O/W emulsions but did not change particle size values, compared to a control with no flavonoids during storage. Quercetin showed the highest antioxidant activity for inhibition of lipid oxidation based on lowered lipid hydroperoxide formation and 2-thiobarbituric acid reactive substances values in emulsions, followed by rutin, hesperitin, and hesperidin. Hesperidin and hesperitin did not affect antioxidative activities in O/W emulsions under metal ion-catalyzed conditions. Addition of hesperidin, hesperitin, rutin, and quercetin to soybean oil O/W emulsions improved the physical and oxidative stability of emulsions lacking added metal ions.     

乳化体系中花生油氧化稳定性的研究

主要探讨花生油乳化体系中乳化剂类型、用量、pH值、EDTA、温度等对花生油氧化稳定性的影响,结果显示:乳化剂种类和pH对于乳状液体系的氧化稳定性有显著影响,阴离子乳化剂SDS稳定的乳化液,pH4.0的氧化速率最快;非离子乳化剂Tween20稳定的乳化液,pH的影响不是很显著;阳离子乳化剂CTAB稳定的乳化液,随着pH的升高,氧化速率变快。乳化液体系中微量金属离子对于体系也有相当大的影响,随着金属离子螯合剂EDTA浓度的增加,其乳化体系中花生油的氧化速率显著降低。乳化剂用量也会影响体系的氧化稳定性,随着乳化剂用量的增加,乳化乳化体系中花生油的氧化稳定性降低。     

Hemp-seed and olive oils: Their stability against oxidation and use in O/W emulsions

Hair treatment chemicals induce sudden and severe hair damage. In this study, we examined cuticles from untreated, permed, and bleached hair that were mechanically discriminated by shaking in water. Both perming and bleaching treatments are prone to easily delaminate cuticles. Confocal microscopy revealed that the cuticles of permed hair were delaminated with larger pieces than untreated ones. On the other hand, the cuticles of bleached hair tend to fragment into small peptides. At the minimum concentration of thioglycolate required to elute S100A3 protein from the endocuticle into the reductive permanent waving lotion, enlarged delaminated cuticle fragments were observed. Although S100A3 is retained in bleached hair, S100A3 is irreversibly oxidized upon bleaching treatment. It is likely that the oxidative cleavage of disulfide bonds between cuticle-constituting proteins, including S100A3, results in the fragile property of cuticles. Here we present a more comprehensive model of hair damage based on a diverse mechanism of cuticle delamination.     

各相体积比对W/O/W复合乳状液性质的影响

目的：研究用两步乳化法制备W／O／W型复合乳状液时，第一相体积比（内水相与油相的体积比）、第二相体积比（初乳与外水相的体积比）对W／O／W型复合乳状液性质的影响；方法：采用两步乳化法制备W／O／W型复合乳状液，固定制备工艺条件，改变第一相体积比和第二相体积比的数值制备初乳和复乳，用离心分层稳定性评价复乳的稳定性，初乳的离心稳定性、黏度和复乳的粒度分布被测定；结果：随着第一相体积分数增大，初乳黏度增大，初乳和复乳的离心稳定性都提高，但是内水相的体积分数达到65％时，初乳表现出凝胶的外观，所制备的复乳的稳定性反而降低，当内水相的体积分数增加到70％的时候，初乳转相形成O／W型乳状液，不能进一步制备复乳；随着第二相体积分数的增大，复乳黏度线性增大，复乳滴的体积平均粒径减小，复乳的离心稳定性提高。初乳中内水相与油相的适宜的体积比及复乳中初乳和外水相的适宜体积比皆为1：1左右。     

O/W乳状液对核桃油氧化稳定性影响的研究

以吐温80和95%乙醇混合物为乳化剂制备核桃油乳状液,研究乳液对核桃油氧化稳定性影响。乳化剂与核桃油质量比为1∶2时,D_(50)为0.95μm,乳化效果最好;相同条件,不添加或添加相同量茶多酚,乳液过氧化值都低于纯核桃油。试验结果说明,乳液对核桃油有很好的氧化保护作用。     

Microwave heating of different commercial categories of olive oil: Part I. Effect on chemical oxidative stability indices and phenolic compounds

The effect of microwave heating of extra virgin olive oil (EVOo), olive oil (Oo) and pomace olive oil (Po) in domestic appliances, was investigated in terms of chemical oxidative indices (peroxide, p-anisidine and Totox values), free acidity, water content, total phenol content and different classes of phenolic compounds.     

Effects of monoacylglycerols on the oxidative stability of olive oil

BACKGROUND: The study of pro‐ and anti‐oxidant compounds is important for their influence on the shelf‐life and nutritional value of food. The aim of this research was to evaluate the activity of monoacylglycerols (MAG), obtained by partial saponification of a purified olive oil, added in increasing amounts to the same oil and submitted to the Rancimat test and oven test at 60 °C. Besides routine analyses, high‐performance size exclusion chromatography analysis of polar compounds was performed. RESULTS: The addition of MAG led in all cases to a significant slowdown of the oxidative processes. These trends were more evident as the oxidation went on. The purified oil added with 30 g kg^?1 of MAG after 9 days of oven test at 60 °C presented a level of oxidative degradation significantly lower than the control after only 4 days. CONCLUSION: The data showed a marked antioxidant effect of MAG in purified olive oil, contrary to what has been observed by other authors, who noticed either a pro‐oxidant or a non‐antioxidant activity of these compounds in soybean oil. A different behaviour of MAG during oxidation could depend on the different fatty acid composition of the oil matter they are added to. Copyright © 2010 Society of Chemical Industry     

碱热改性米渣谷蛋白对W/O/W型双重乳液稳定性的影响

目的：实现米渣谷蛋白在乳浊体系中的应用。方法：选取碱热改性米渣谷蛋白和span80,采用一步乳化法制备W/O/W型双重乳液,并考察蛋白浓度对双重乳液稳定性的影响。结果：当蛋白质量分数从0.5%升高至2.5%时,乳液大粒径峰消失,显微结构中液滴的双重结构增强,表观黏度及黏弹性提高,离心稳定性和贮藏稳定性增强。当蛋白质量分数为2.5%时,离心后乳清析出指数从37.21%降至10.56%,分层时间从6 h延长至96 h。蛋白质与span80形成复合膜共同稳定油水界面,形成中间态液滴,当界面蛋白足以形成刚性界面膜时,液滴从中间态转为稳定的双重结构;当蛋白质量分数为3.0%时,双重乳液发生絮凝使大粒径峰重新出现,稳定性下降,离心后乳清析出指数为16.48%,制备后96 h左右分层,过剩的蛋白质一部分参与内相液滴的构建,另一部分单独形成O/W型液滴吸附于大体积液滴外侧。结论：一步乳化法下,蛋白质量分数为2.5%时,可制得稳定双重乳液。     

油茶籽油不同形态酚类化合物对油脂氧化稳定性的影响北大核心CSCD

为阐明酚类化合物的抗氧化机理及利用其协同增效作用延缓油脂氧化,对油茶籽油中游离酚(free phenolics,FP)、酯化酚(esterified phenolics,EP)及不溶性结合酚(insoluble-bound phenolics,ISP)的提取工艺进行优化,并采用Schaal烘箱法研究不同形态酚类化合物单独或复配作用对油茶籽油氧化稳定性的影响,分析不同形态酚类化合物的互作关系。结果表明:FP的最优提取工艺条件为料液比1∶15、提取温度45℃、提取时间1.5 h、提取次数3次,EP的最优提取工艺条件为碱解液与乙酸乙酯体积比1∶1、萃取次数3次,ISP的最优提取工艺条件为NaOH浓度0.25 mol/L、料液比1∶3、碱解时间6 h、碱解温度45℃。在最优条件下,油茶籽油中FP、EP及ISP含量分别为(43.43±2.05)mg/kg、(28.67±1.51)mg/kg及(65.87±1.34)mg/kg。不同形态酚类化合物均具有抑制氧化产物生成,增强油脂氧化稳定性的作用,其中EP+ISP的抗氧化性最强。各互作组分在油脂中均呈一定的拮抗作用,其中FP+EP+ISP的拮抗作用最强。     

The influence of different stabilizers and salt addition on the stability of model emulsions containing olive or sesame oil

Stabilizers are widely used in low-fat emulsion production. However, food industry pays attention to ingredients, such as resistant starch (RS) that also present substantial benefits to human health. Low-fat model emulsions of either olive or sesame oil that also contained xanthan gum (XG), whey protein concentrate (WPC), and undigested (resistant) starch (RS) were produced and stored at 5 °C. Salt was added in selected samples. A multiple light scattering technique was applied for investigating destabilization phenomena. Microscopic observations and droplet size measurements took place. Rheological properties performing a heating–cooling cycle experiment (5–25–5 °C) were measured. Olive oil emulsions presented the greatest stability and the lowest droplet size. RS plays the role of solid particle stabilizer, mainly entrapped in the matrix of the continuous phase. By salt addition stability was significantly improved, whereas droplet size was decreased. Those samples had a more pronounced elastic character and significantly greater viscosity values than their counterparts without salt.     

橄榄油极性酚类物质对降血脂作用探究

极性酚类物质是橄榄油重要不皂化物之一。酚类物质不仅赋予橄榄油特殊风味、提高油脂氧化稳定性,并具有良好清除自由基和阻止低密度脂蛋白(LDL)氧化能力,从而能降血脂、有效预防心血管疾病发生。该文主要从体外实验、动物实验和人体餐后实验综述橄榄油酚类物质降血脂功效。     

大豆油乳状液体系氧化稳定性影响因素的研究

研究了乳状液体系中不饱和脂肪酸的氧化机制，重点探讨了乳化剂种类、用量、pH和EDTA对大豆油乳化体系（O／W）氧化稳定性的影响。结果显示：乳化剂种类和pH对于乳状液体系的氧化稳定性有显著影响，对于阴离子乳化剂SDS稳定的乳状液，pH4．0的氧化速率比pH7．0和9．0快得多；对于非离子乳化剂Tween20稳定的乳状液，pH的影响不显著；对于阳离子乳化剂CTAB稳定的乳状液，随着pH的升高，氧化速率变快；同时在pH4．0条件下，氧化速率SDS〉CTAB〉Tween20，而在pH7．0和9．0条件下，氧化速率CTAB〉SDS≌Tween20。乳状液体系中自带的微量金属离子对于体系也有相当大的影响，随着金属离子螯合剂EDTA浓度的增加，其乳状液氧化速率显著降低。乳化剂用量也会影响体系的氧化稳定性，随着乳化剂用量的增加，乳状液的氧化稳定性变差，这种稳定性的弱化是由于粒径变小、油滴表面积增大引起的。     

Droplet characterization and stability of soybean oil/palm kernel olein O/W emulsions with the presence of selected polysaccharides

Droplet characteristics, flow properties and stability of egg yolk-stabilized oil-in-water (O/W) emulsions as affected by the presence of xanthan gum (XG), carboxymethyl cellulose (CMC), guar gum (GG), locust bean gum (LBG) and gum Arabic (AG) were studied. The dispersed phase (40%) of the emulsions was based on soybean oil/palm kernel olein blend (70:30) that partially crystallized during extended storage at 5 °C. In freshly prepared emulsions, the presence of XG, CMC, GG and LBG had significantly decreased the droplet mean diameters. XG, LBG, GG and CMC emulsions exhibited a shear-thinning behavior but AG emulsion exhibited a Bingham plastic behavior and control (without gum) emulsion almost exhibited a Newtonian behavior. Both control and AG emulsions exhibited a severe phase separation after storage (30 days, 5 °C). The microstructure of stored XG emulsion showed the presence of partially coalesced droplets, explaining a large increase in its droplet mean diameters. Increases in droplet mean diameters and decreases in flow properties found for stored GG and LBG emulsions were attributed to droplet coalescence. Nevertheless, the occurrence of droplet coalescence in these emulsions was considered to be small as no free oil could be separated under centrifugation force. Increases in flow properties and excellent stability towards phase separation found for stored CMC emulsion suggested that CMC could retard partial coalescence. Thus, the results support the ability of CMC, GG and LBG in reducing partial coalescence either by providing a sufficiently thick continuous phase or by acting as a protective coating for oil droplets.     

Study of commodity properties of food emulsions Part 1. The effect of dispersion medium composition on kinetic stability of O/W emulsions containing proteins,acidic polysaccharides and calcium salts

The effect of concentrations of acidic polysaccharide and calcium ions on the kinetic stability, viscosity and dispersity of protein-containing O/W emulsions is studied. Variation of kinetic stability of the emulsions studied is independent of dispersion composition. In a wide range of calcium acetate concentrations a correlation is observed between kinetic stability and viscosity of emulsions at sodium alginate concentration in the dispersion medium ≤ 0.3%. The transition zone between liquid solution and gel is widened in the presence of sodium caseinate. Maximum kinetic stability is reached at calcium acetate: sodium alginate concentrations of 1.0-1.2 and ～ 6.0, corresponding to optimum conditions for formation of homogeneous crosslinked structures of calcium alginate and calcium caseinate.     

Influence of the malaxation time and olive ripening stage on oil quality and phenolic compounds of virgin olive oils

The main objective of this study was to evaluate the influence of the malaxation time (Mt) and ripening stage on oil quality and phenolic compounds of Hojiblanca and Picual virgin olive oils. In both varieties of oil, phenolic content and oxidative stability decreased as ripening progressed. The total level of tocopherols diminished by up to 40% as fruit ripened. The compositions of palmitic, stearic, lignoceric, oleic, linoleic and linolenic acids were significantly influenced by the ripening process. The present work shows that an increased Mt promoted the increase of free acidity (up to 13.3%) and tocopherols (up to 11.6%) and negatively affected the oxidative stability and the concentration of phenols. Further research is required to determine ripening stages and malaxation conditions for all olive oil varieties to achieve a satisfactory balance between the improvement of both oil yield and oil quality and composition.     

Effect of standard phenolic compounds and olive oil phenolic extracts on acrylamide formation in an emulsion system

In this work the effect of standard phenolic compounds such as trolox, phenolic acids (ferulic, gallic, protocatechuic and caffeic acid) and secoiridoids, extracted from virgin olive oil (VOO), on acrylamide formation in an emulsion system was investigated. The emulsion system was heated in an oil bath at different temperatures and for different periods of time. At 105 and 115 °C the generated amounts of acrylamide were negligible during the monitoring time. At 125 °C addition of standard phenolic compounds reduced acrylamide formation which was more pronounced at initial time of heating (20 min) reaching up to 70%. Protocatechuic and gallic acid were more effective than trolox, caffeic and ferulic acid in acrylamide reduction at the final time intervals of heating (30–60 min). On the contrary, addition of VOO extract in the emulsion system resulted in a remarkable increase of acrylamide level, which was ascribed to secoiridoids’ structure containing aldehydic groups.