葵花籽蛋白水解物对水包油型乳状液物理和氧化稳定性的影响

利用碱性蛋白酶对葵花籽蛋白进行适度水解后,将葵花籽蛋白水解物(SSH)添加到以单甘酯作为乳化剂制备的乳状液中,通过测定乳状液的乳化活性、乳化稳定性、粒径、絮凝指数、凝结指数以及乳状液贮藏14 d过氧化值和丙二醛含量的变化,评价SSH对乳状液物理和氧化稳定性的影响。结果表明:添加SSH可显著提高乳状液的乳化活性、乳化稳定性、絮凝和凝结稳定性,显著降低乳状液的粒径;SSH添加量为1.0%时,乳状液具有较好的物理稳定性,同时又具有较好的氧化稳定性。     

美藤果油水包油型乳液的制备及其稳定性研究

应用高压匀质法制备美藤果油水包油型乳液。以乳液的平均粒径和分散系数(PDI)为指标,探究Tween乳化剂类型、油质量分数、乳化剂添加量、剪切速率及均质压力对乳液的平均粒径以及PDI的影响。通过测量储藏期内乳液的粒径变化、油相氧化程度(过氧化值和硫代巴比妥酸含量)、液滴的自扩散系数以及游离脂肪酸含量变化,进一步探究储藏期内乳液的物理、氧化以及水解稳定性。结果表明:制备乳液的优化工艺条件为Tween60添加量1%、油质量分数10%、剪切速率16 000 r/min、均质压力40 MPa,此条件下制备的乳液平均粒径为(218. 27±2. 21) nm,PDI为0. 118±0. 002;该工艺条件下制备的美藤果油乳液在14 d的储藏期间内具有较好的耐受pH、盐离子的物理稳定性和较高的氧化稳定性,并且未发生明显的水解作用。     

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.     

三种乳化剂对橄榄油乳液稳定性的影响

乳化剂因亲水亲油平衡值的不同对油脂乳化效果表现出固有的差异,但这种差异会因加入辅助剂的影响而发生改变。以非离子型表面活性剂单甘酯、蔗糖酯和吐温20为乳化剂,以白果直链淀粉及阿拉伯胶(质量比1∶1)为辅助剂,对橄榄油进行乳化,考察了辅助剂加入前后在不同制备方法(先油后水和先水后油工艺)和乳化剂添加量下乳液的稳定性。结果表明:单独使用乳化剂时,经外观观察,在三种乳化剂添加量相同时,吐温20的橄榄油乳液稳定性较好,其次为蔗糖酯、单甘酯;加入辅助剂后,乳液的乳化状态较单一加入乳化剂的好,乳液黏度、粒径和浑浊度均随着乳化剂添加量的增大呈先减小后增加趋势,且在相同添加量下,由蔗糖酯制备的橄榄油乳液黏度较低,粒径和浑浊度较小,稳定性较好,吐温20及单甘酯次之;辅助剂加入前后,先油后水工艺制备的橄榄油乳液的稳定性总体优于先水后油工艺的。     

Isolation, characterization and emulsion stabilizing properties of polysaccharides form orchid roots (salep)

Polysaccharide extracts were isolated from ground salep (dried orchid root). These were studied in terms of their composition and their capacity to affect the rheology and stability of emulsions. Successive extractions yielded three separate extracts, namely HBSS (hot buffer soluble solids, extracted at 70 °C, pH = 5.2), CHSS (chelating agent soluble solids, extracted at 70 °C, pH = 5.2), and DASS (diluted alkali soluble solids, extracted at 0 °C). HBSS comprised of negatively charged macromolecular populations sizing approximately between 600 kDa-700 kDa (d ∼ 500 nm), one at 50 kDa (d ∼ 70 nm), and a third one at 12 kDa (d ∼ 20 nm). Upon addition into Tween 20-stabilized emulsions, HBSS caused flocculation and enhanced creaming at low concentrations (0.1%), while at higher concentrations (≥0.7%) it drastically reduced creaming due to the increase of the aqueous phase viscosity.CHSS extracts contained a negatively charged polysaccharide population of approximately 50 kDa (d ∼ 140 nm). DASS extracts contained only small molecules. Addition of CHSS or DASS extracts into Tween 20-stabilized emulsions did not affect the viscosity or the creaming stability of the emulsions. Flocculation was induced at 2% CHSS. This can be predicted by a simple depletion model. The above suggest that salep hydrocolloids are highly efficient thickeners that can be extracted in a one-step process.     

均质条件与大米饮料乳化稳定性关系研究

探讨了不同的均质条件对油滴粒径分布的影响及与乳化液稳定性之间的关系。结果证明,在均质压力为两次40MPa,均质温度为60℃下,乳化体系最为稳定,利于大米饮料保持良好的外观稳定性。     

Whey protein–carboxymethylcellulose interaction in solution and in oil-in-water emulsion systems. Effect on emulsion stability

Carboxymethylcellulose (CMC) was used as coagulation aid to precipitate the whey proteins from defatted milk serum and the ability of the resulting whey protein concentrate (WPC, protein content: 63.69%) to aid in the physicochemical stabilization of oil-in-water emulsions, during ageing or following the application of heat or freeze–thaw treatment, was investigated, along with the stability of emulsion systems prepared with a commercial whey protein isolate. The stability of WPC emulsions against droplet flocculation and creaming, and to a lesser extent against droplet coalescence, depended on the presence of the CMC molecules in the emulsion continuous phase and the extent of adsorbed protein–polysaccharide interactions as affected by the emulsion pH. Studies on whey protein–CMC interaction were conducted, both in biopolymer mixture solutions and emulsion systems, by applying zeta potential measurement and viscometry techniques. These results were combined with data on protein surface hydrophobicity and on methylene blue-binding ability of CMC molecules and indicated that whey protein–CMC interaction may take place in solution, both at neutral as well as at acidic environments, leading, depending on pH, to the formation of soluble or non-soluble amphiphilic conjugates. In emulsion systems, however, conjugate formation is observed only at relatively acidic pH environments, probably because at a neutral or at a slightly acidic pH whey protein adsorption to the emulsion droplet surface and molecular unfolding does not favour protein–polysaccharide interaction.     

高稳定性蔗糖聚酯乳液的制备及其应用

为优化蔗糖聚酯的乳化工艺,提高其乳液的稳定性,采用转相乳化法,研究了复合乳化剂HLB值、用量、油水比例、乳化时间、乳化温度及搅拌速度对蔗糖聚酯乳化效果的影响,并对蔗糖聚酯乳液的稳定性和应用性进行了研究。结果表明,最佳的乳化条件为：复合乳化剂HLB值为9.8,用量为9%,乳化水油比例为2,乳化时间85 min,乳化温度30 ℃,剪切速率2000 r/min;该蔗糖聚酯乳液具有高稳定性和良好分散性,粒径分布均匀,长期放置不分层,且该蔗糖聚酯乳液能够有效降低织物表面摩擦因数,赋予织物良好的柔软效果,对织物色变影响较小。     

几种乳化剂对软冰淇淋基料乳状液稳定性的影响

通过对几种乳化剂在软冰淇淋基料中应用的研究发现添加乳化剂可以有效改善软冰淇淋基料的稳定性,延长其保质期。结果表明,当添加0.4%(质量分数,下同)左右的单甘油酯时;聚甘油脂肪酸酯(半固态)或二乙酰酒石酸单甘酯(固态)添加量为0.2%时;柠檬酸单甘油酯的添加量为0.07%时,软冰淇淋基料的黏度最低、粒径最小,并且可有效延长软冰淇淋基料的稳定期。而添加乙酰基单甘酯即使在样品黏度最低、粒径最小时,仍然不能很好的稳定料液,因此不适合用于稳定软冰淇淋基料。另外经过本实验的比较发现熔点较高的乳化剂可有效促进脂肪结晶,改善冰淇淋成品的品质。     

Contribution of okra extracts to the stability and rheology of oil-in-water emulsions

Three okra polysaccharide extracts were isolated and studied in terms of their composition and their capacity to affect the rheology and stability of emulsions. HBSS (hot buffer soluble solids, extracted at 70 °C, pH = 5.2) comprised of charged (zeta potential −21.5 mV) polysaccharides sizing between 5 kDa (d ∼ 3 nm) and 50 kDa (d ∼ 200 nm), and a population of very large molecules (MW >> 1.4 MDa). Upon addition in Tween 20-stabilized emulsions, HBSS caused flocculation and enhanced creaming at low concentrations (0.125%), while at higher concentrations (1.25%–2.50%) it drastically reduced creaming due to its increase of the continuous phase viscosity.     

甜菜果胶制备藻油乳化液及其稳定性研究

藻油富含对人体非常重要的多不饱和脂肪酸DHA（二十二碳六烯酸）,但其极易被光、热和氧等因素诱使发生氧化反应。防止氧化反应发生,制备成稳定的油／水乳化液将其包埋成为其在食品中应用的关键问题。本研究采用甜菜果胶为乳化剂对其进行乳化包埋,研究了乳化条件如乳化剂量、油水比率、pH和均质条件对乳化液稳定性的影响。结果表明,最适的乳化条件为：乳化剂添加量在2．5％以上,油水比1：10,pH〉5,35MPa压力下均质3个循环得到比较稳定的乳化液。     

Emerging drying techniques for food safety and quality: A review

The new trends in drying technology seek a promising alternative to synthetic preservatives to improve the shelf-life and storage stability of food products. On the other hand, the drying process can result in deformation and degradation of phytoconstituents due to their thermal sensitivity. The main purpose of this review is to give a general overview of common drying techniques with special attention to food industrial applications, focusing on recent advances to maintain the features of the active phytoconstituents and nutrients, and improve their release and storage stability. Furthermore, a drying technique that extends the shelf-life of food products by reducing trapped water, will negatively affect the spoilage of microorganisms and enzymes that are responsible for undesired chemical composition changes, but can protect beneficial microorganisms like probiotics. This paper also explores recent efficient improvements in drying technologies that produce high-quality and low-cost final products compared to conventional methods. However, despite the recent advances in drying technologies, hybrid drying (a combination of different drying techniques) and spray drying (drying with the help of encapsulation methods) are still promising techniques in food industries. In conclusion, spray drying encapsulation can improve the morphology and texture of dry materials, preserve natural components for a long time, and increase storage times (shelf-life). Optimizing a drying technique and using a suitable drying agent should also be a promising solution to preserve probiotic bacteria and antimicrobial compounds.     

Effect of blackberry and raspberry juice on whey protein emulsion stability

The effect of raspberry and blackberry juice on oil-in-water (o/w) emulsion oxidative stability was investigated with different concentrations of whey proteins and rapeseed oil. The extent of lipid oxidation was measured by determining conjugated diene hydroperoxides and thiobarbituric acid reactive substances and that of protein oxidation by loss of natural tryptophan fluorescence and formation of protein carbonyl compounds. In addition, the anthocyanin colour stability and emulsion turbidity were measured. The increasing concentration of whey proteins and berry juices led to enhanced stabilization of the interface formed during emulsification. The anthocyanin concentration and colour decreased during oxidation leading to whiter emulsions. Raspberry juice provided a better overall antioxidant protection towards lipid and protein oxidation compared to blackberry juice. The antioxidant activity of berry juices towards lipid oxidation varied with concentration. The antioxidant activity increased with increasing concentration of berry juices. In conclusion, red berry juice anthocyanins, as well as other phenolic compounds, act as antioxidants improving the oxidative stability of whey protein emulsions. However, the antioxidant protection is different towards protein and lipid oxidation, and is also affected by other components present.     

pH, Na₊和Ca₂₊对大豆种皮果胶类多糖乳化稳定性的影响

本研究主要探讨pH值和金属离子对大豆种皮果胶类多糖制备水包油乳液的物理稳定性影响。利用草酸铵法制备大豆种皮果胶类多糖(Soybean Hull Pectic Polysaccharide, SHPP),确定平均粒径、动态流变性质及显微形态以获得关于稳定机制的更多信息。结果表明,pH值和金属离子对SHPP的乳化稳定性均有显著影响。pH值由3.0至7.0,SHPP的乳化稳定性先升高后降低。在pH值为4.0时,乳化颗粒粒径及脂肪上浮率最小,分别为15.67μm、31%,乳液表观黏度及乳化稳定性最好。添加Na₊和Ca₂₊均可降低乳液乳化稳定性,0.2 mol/L Na₊对乳液乳化稳定性影响较大,而0.05 mol/L Ca₂₊次之。     

纯胶在橘油乳化香精中的应用及其稳定性的比较

将三种纯胶应用于橘油乳化香精中,比较乳化香精的粒径大小、分布、稳定性和应用的差异。结果表明,纯胶的表观黏度值越大,则制备乳化香精的平均粒径和峰宽相对越大,稳定性越低。三种乳化香精在不同环境温度下存放20d左右时,吸光值均达到最大值;存放30d后,吸光值均基本趋于稳定。20℃常温储存有利于乳化香精的稳定;含纯胶B、C的乳化香精在各储存条件下的稳定性均较好。通过在无醇饮料中的应用实验表明,三种乳化香精均较适合使用在pH值≤3的酸性体系中;在pH=4.0时,含纯胶B乳化香精的稳定性相对最好;在pH=3.0时,含纯胶B、C乳化香精的稳定性相对纯胶A较好;在pH=2.0时,三种乳化香精在存放20d后的吸光值均基本趋于稳定。     

Effect of chitosan on the stability and properties of modified lecithin stabilized oil-in-water monodisperse emulsion prepared by microchannel emulsification

The effect of chitosan (CHI) on the stability of monodisperse modified lecithin (ML) stabilized soybean oil-in-water (O/W) emulsion was investigated. Monodisperse emulsion droplets with particle size of 24.4 ± 0.7 μm and coefficient of variation below 12% were prepared by microchannel (MC) emulsification using a hydrophilic asymmetric straight-through MC silicon 24 × 24 mm microchip consisting of 23,348 microchannels. The stability of the ML stabilized monodisperse emulsion droplets was investigated as a function of CHI addition at various concentration, pH, ionic strength, thermal treatment and freezing-thawing treatment by means of particle size and ζ-potential measurements as well as microscopic observation. The monodisperse O/W emulsions were diluted with CHI solution at various concentrations to a final droplet concentration of 1 wt% soybean oil, 0.25 wt% ML and 0–0.5 wt% CHI at pH 3. Pronounced droplet aggregation was observed when CHI was present at a concentration range of between 0.01 and 0.04 wt%. Above this concentration range, flocculations were less extensive, indicating some restabilization. ML stabilized emulsions were stable at a wide range of NaCl concentrations (0–1000 mM) and pH (3–8). On the contrary, in the presence of CHI, aggregation of the emulsion droplets was observed when NaCl concentration was above 200 mM and when the pH started to approach the pKa of CHI (i.e. ∼6.2–7.0). Emulsions containing CHI were found to have better stability at high temperature (>70 °C) in comparison to the emulsion stabilized only by ML. With sucrose/sorbitol as cryoprotectant aids, emulsions with the addition of CHI were found to be more resistant to droplet coalescence as compared to those without CHI after freezing at −20 °C for 22 h and thawing at 30 °C for 2 h. The use of CHI may potentially destabilize ML-stabilized O/W emulsions but its stability can be enhanced by selectively choosing the appropriate CHI concentrations and conditions of preparation.     

Relating the effect of saliva-induced emulsion flocculation on rheological properties and retention on the tongue surface with sensory perception

Perception of food emulsions can often not be directly related to the structure of the products before consumption. Taking into account the changing product structure upon oral processing might increase understanding of the relation between perception and product properties.     

大米饮料乳化体系中油脂粒径分布与乳化液稳定性关系的研究

在大米饮料制作过程中,为获得较稳定的乳化体系采用了不同的油/水分散方法.重点研究了不同分散方法对油滴大小的分布的影响及与乳化液稳定性之间的关系.结果证明,乳化油滴大小在70～80nm之间时,乳化体系最稳定,利于大米饮料保持良好的外观稳定性.     

Bubble stability in the presence of oil-in-water emulsion droplets: Influence of surface shear versus dilatational rheology

We discuss the stability of bubbles to coalescence when undergoing a pressure drop and their stability to disproportionation under quiescent conditions, studied using previously established ‘single bubble layer experimental’ techniques, focussing on the effects on stability of the inclusion of a low volume fraction (0.25%) of stable oil droplets. Detailed measurements of the surface dilatational elasticity (?_s) and surface shear viscosity (η_s) of systems in the presence and absence of oil droplets have been performed. The surface rheology and stability have been measured as a function of adsorption time and pH, between pH 4.5 and 7, by including glucono-δ-lactone (GDL) as an acidification agent. Commercial sodium caseinate (SC) and purified β-lactoglobulin (β-L) were used at 1 wt% bulk concentration as bubble stabilizing agents. The emulsion oil droplet phase was n-tetradecane (TD) or 1-bromohexadecane (BHD), with a mean droplet size of (d₄₃) = 0.59 and 0.67 μm, respectively. The emulsion droplets were completely stable to coalescence and did not enter or spread at the air–water (A–W) interface. With SC at all pH values the values of η_s were markedly higher in the presence of TD droplets than in their absence, but particularly when the pH was lowered to pH ≤ 5.5 such that the SC started to aggregate. The increase in η_s correlated with the increase in coalescence stability under the same conditions. With neutrally buoyant BHD droplets the increase in η_s was not as great, but η_s was still significantly higher than in the absence of droplets, indicating that the rise to, and packing of, TD droplets at the A–W interface due to gravity was not solely responsible for their observed effects. The values of ?_s did not increase much at all for either β-L or SC as the pH was lowered and/or TD droplets were added, except at very low pH values, when the effects with SC were obscured by the tendency for the bulk SC to gel. In agreement with the relatively insignificant changes in ?_s as the pH was lowered or droplets were added, the resistance to disproportionation of bubbles did not change very much either.     

浮选脱墨时泡沫的稳定性及其带走纤维和填料的问题

介绍了油墨粒子大小和气泡大小与数量及其形成的泡沫的稳定性等对浮选脱墨效率和浮选得率的影响。结果认为：浮选时适当的油墨粒子大小和适当的气泡大小形成稳定的泡沫层，对提高浮选脱墨效率是非常重要的。气泡间的水会带走纤维和填料造成浮选得率降低是值得重视的。