Comparative study of Pickering emulsions stabilised by starch particles from different botanical origins

Starch botanical origin is a key factor for the characteristics of Pickering emulsion. Starches with different sizes from rice (2.9–7.6 µm), waxy corn (9.3–25.0 µm), wheat (11.4–33.7 µm) and potato (24.4–54.1 µm) were esterified by octenyl succinic anhydride. The modified starch particles were used as stabilisers to produce oil-in-water Pickering emulsions. The physical stability, microstructures and rheological properties of different emulsions were compared. Results indicated that the emulsion stabilised with rice starch particles had the minimum droplet size of 83.6 µm and best physical stability during 30 days of storage. Moreover, starch particle size was negatively correlated with emulsion stability (P < 0.05). The particles (3.85% of the emulsion, w/w) built up wall-like structures around oil droplets, which prevented them from freely moving. All emulsions showed pseudoplastic fluid behaviours and presented gel properties, but elastic modulus (G′) and loss modulus (G″) were mainly affected by starch botanical origins.     

Starch particles for food based Pickering emulsions

Intact starch granules are a new source of particles for stabilizing emulsions, so called Pickering emulsions. Small (1-2 μm) and uni-modal starch granules at various concentrations have been used in this study to investigate the stability of the emulsions, the drop size dependence of the starch concentration and the barrier properties of the stabilizing starch layer upon heating. The granules were modified with octenyl succinic anhydride (OSA) to increase the hydrophobicity. The drops in the emulsions prepared in this study were in the 10-100 μm range depending on the starch concentration, and the drop size decreased with an increased amount of added starch granules. During the 8 week storage, the emulsion drops were stable to coalescence and the volume occluded by the emulsion phase was unaffected or even increased. In order to increase the barrier properties at the oil-water interface the emulsions were gently heated, which induced a partial gelatinization of the starch granules. The efficiency of the barrier was characterized by a lipolysis experiment where the activity of lipase was measured. The activity of lipase was decreased with nearly 70% compared to an unheated starch stabilized emulsion, which will be useful in applications where a controlled release of specific substances in the gastro intestinal tract is desirable.     

Chloroplast thylakoid membrane-stabilised emulsions

BACKGROUND: Thylakoid‐stabilised emulsions have been reported to possess satiety‐promoting effects and inhibit pancreatic lipase–colipase activity in vitro, which prompted the investigation of their interfacial properties. RESULTS: Thylakoid membranes isolated from spinach were used as an emulsifier/stabiliser in oil (triglyceride)‐in‐water emulsions. Emulsions were characterised with respect to droplet size, interfacial tension, creaming, surface load and electron microscopy. The effects of pH and thylakoid concentration were also considered. Droplet size decreased with increasing thylakoid concentration, reaching a plateau around 15 µm beyond concentrations of 2 mg protein mL^?1 oil. The resulting emulsions were stable against coalescence but were subject to creaming. The surface pressure (air/water interface) of the thylakoid isolate was 44 mN m^?1 and the surface load 13 mg m^?2 at 10 mg protein mL^?1 oil. Electron micrographs showed thylakoids adsorbed as bunched vesicles on the drop surfaces. The stabilisation mechanism can be described as a combined effect of surface‐active molecules, mainly membrane proteins but also membrane lipids, exposed on surfaces of thylakoid membrane vesicles adsorbed as particles. CONCLUSION: Thylakoid membranes effectively stabilise oil‐in‐water emulsions, which should facilitate their incorporation in food with satiety‐promoting effects. To the authors' knowledge, this is the first study on the emulsifying properties of an isolated biological membrane as a functional ingredient. Copyright © 2010 Society of Chemical Industry     

球磨-酯化复合改性槟榔芋淀粉对Pickering乳液形成的影响

为了提高淀粉颗粒的乳化能力,以球磨-酯化复合改性槟榔芋淀粉为颗粒乳化剂,大豆油为油相,制备水包油型Pickering乳液.采用激光粒度仪、研究级正置显微镜、流变仪等对Pickering乳液外观、液滴粒径、显微形态及动态流变特性进行表征,考察淀粉颗粒质量浓度(1、5、10、20、30 mg/mL)和油相体积分数(10％、...     

Formation of oil‐in‐water (O/W) pickering emulsions via complexation between β‐cyclodextrin and selected organic solvents

Cyclodextrins (CDs) are cyclic oligosaccharides derived from the enzymatic degradation of starch. Emulsifying functionality of β‐cyclodextrin (β‐CD) upon its complexation with selected solvents (octanol, decane, and toluene) was studied. In several tests, the three‐phase systems containing the emulsion fraction in the middle position were obtained. The examination of variations in the phase behavior of the test systems showed that the decane/β‐CD/water system had the highest emulsion phase volume when β‐CD at concentration of 10% w/v was used. A reduction in interfacial tension (IFT) of the oil–water interface in each test system was observed with the following order: toluene, decane, and octanol. The precipitated fraction obtained upon centrifugation of the emulsion phase, was structurally characterized as the inclusion complex (IC) formed between β‐CD and each of the three test solvents. The wettability of the IC particles was determined through contact angle measurement and formation of the oil‐in‐water (O/W) Pickering emulsions was confirmed (θ_ow<90°). With use of size distribution data, the ICs particles as the microparticles (1–10 µm) were found to be the main species involved in the formation and stabilization of the emulsions.     

玉米纤维素在Pickering乳液制备中的应用研究

由超细固体颗粒取代普通乳化剂制备的Pickering乳液发展迅速。采用淀粉酶、糖化酶以及中性蛋白酶处理玉米麸皮得到了纯度相对较高的玉米纤维素,以大豆油为模式油相,以显微形态、外观和贮藏稳定性为指标,对玉米纤维素制备Pickering乳液的可能性及条件进行了研究。结果表明,玉米纤维素具有稳定大豆油乳液的能力,且最适条件为油水体积比5∶5、分散转速11 000 r/min、分散时间7 min、分散温度10℃、纤维素添加量0.015%(m/V)。在此条件下制备的大豆油Pickering乳液外观均一,贮藏过程中无明显的析油及析乳现象。因此,玉米纤维素在新型Pickering乳液的开发中具有较好的应用潜力。关键字     

Starch‐Soybean Oil Composites With High Oil: Starch Ratios Prepared By Steam Jet Cooking

Aqueous mixtures of soybean oil and starch were jet cooked at oil: starch ratios ranging from 0.5:1 to 4:1 to yield dispersions of micron‐sized oil droplets that were coated with a thin layer of starch at the oil‐water interface. The jet cooked dispersions were then centrifuged at 2060 and 10,800×g, the buoyant, high‐oil fractions that rose to the surface were isolated, and the size distributions of the oil droplets were determined. Experiments were conducted with normal dent, waxy, and high‐amylose corn starches; and oleic acid was added during jet cooking to form helical inclusion complexes with amylose. With normal dent and waxy corn starches, nearly all of the oil was recovered in the buoyant layers, and only small amounts of oil were found in the aqueous mid layers and settled solids. Oil droplet diameters in the buoyant layers obtained with normal dent and waxy corn starch ranged from under 5 µm to over 50 µm. Centrifugation at high versus low relative centrifugal force produced only minor differences in the droplet size distributions. With high‐amylose starch, microscopy showed that most of the oil droplets were entrapped within aggregates of sub‐micron particles that were apparently formed from amylose‐oleic acid inclusion complexes when the dispersions were cooled. Droplet sizes increased with an increase in the oil: starch ratio, and decreased when oleic acid was added during jet cooking.     

Depletion Flocculation of Beverage Emulsions by Gum Arabic and Modified Starch

ABSTRACT: The creaming velocity, apparent viscosity, and ultrasonic attenuation spectra (1 to 50 MHz) of 5 wt% n hexadecane oil-in-water emulsions containing different droplet radii (r = 0.15 - 0.7 μm), biopolymer types (gum arabic or modified starch), and biopolymer concentrations (0 to 2.5 wt%) were measured. Depletion flocculation was observed in the emulsions when the nonabsorbed biopolymer concentration exceeded a critical concentration (CFC). The CFC increased with decreasing droplet radius for both biopolymers because the magnitude of the depletion attraction increases with droplet size. The CFC was lower for gum arabic than modified starch because it has a higher effective volume in solution. Depletion flocculation led to an increase in creaming instability and apparent viscosity of the emulsions. Flocculation could be nondestructively monitored by measuring the decrease in ultrasonic attenuation of the emulsions. These results show that depletion flocculation by gum arabic and modified starch can have an adverse effect on the stability of beverage emulsions.     

超细化豆渣作为皮克林乳液稳定剂的特性研究

将普通粉碎豆渣进行湿法超细化处理,研究超细化豆渣作为皮克林乳液稳定剂的特性,考察颗粒浓度、油相体积分数、pH及离子强度对乳液液滴尺寸、稳定性和流变学性质的影响。研究发现,超细化提升了豆渣颗粒的悬浮稳定性,且当油相分数φ=0. 6,水相中豆渣颗粒质量分数≥0. 4%时,形成皮克林乳液的粒径为80～140μm,在1～30 d存放期内乳析指数未发生显著变化。水相pH=7时乳液的粒径最大,pH降低时乳液的平均粒径呈单调递减,且乳液稳定性增强。水相中NaCl浓度在100～350 mmol/L对乳液粒径无显著影响。研究还表明,超细化豆渣稳定的皮克林乳液为剪切变稀型流体,其流变学特性受颗粒添加量及水相pH的影响。此研究表明,超细化豆渣具有良好稳定O/W型皮克林乳液的能力。     

Oil/fat blending strategy for improving milk fat globule membrane stability and its effect on fatty acid composition

This study examined the effect of blending with cumin essential oil (CEO) on the stabilisation of milk fat globule membrane (MFGM) emulsions, as well as the particle migration rate, fatty acid composition and phospholipid content after pasteurisation. Blending the MFGM with 20% CEO at pH 6.6 (CM4) led to a decrease in the creaming rate. With increasing CEO ratio, the creaming measurements increased to a 30 mm height with 20% CEO at pH 5.5 (CM3) from 25 mm with 10% CEO at pH 5.5 (CM2). The CM4 migration rate was 0.55 mm/h, and this sample showed no significant forward movement during implementation. The droplet size increased with increasing CEO ratio from 1.69 to 2.07 µm. A total of 20% CEO at pH 6.6 (CM4) was the best blending condition for MFGM stabilisation. This study showed enhanced creaming rate and droplet size, indicating greater destabilisation of the MFGM emulsion, when the CEO ratio was increased.     

Emulsifying properties of gum kondagogu (Cochlospermum gossypium), a natural biopolymer

BACKGROUND: Natural polymers are widely used as emulsifying agents in the food and pharmaceutical industries because of their low cost, biocompatibility and non‐toxic nature. In the present study, emulsifying properties of the novel natural biopolymer gum kondagogu (GKG) were investigated. GKG solutions of different concentrations (0.1–0.6% w/v) were prepared in water and emulsified with liquid paraffin oil (40% v/v) in a high‐speed homogeniser. Flow properties of the emulsions were measured using a rheometer. Emulsion stability and droplet size distribution were determined by visual observation, photomicrography and laser‐scattering particle size distribution analysis. RESULTS: The emulsions prepared with GKG showed pseudoplastic behaviour. The size of oil droplets and the viscosity of emulsions at concentrations of 0.4–0.6% w/v showed little change over time (up to 30 days), indicating that the emulsions were stable. Measurements of the zeta potential of emulsions adjusted to different pH, with and without added electrolyte, showed that the stabilisation of emulsions with GKG was due to mutual repulsion between electrical double layers of particles and adsorption of macromolecules on oil droplets. CONCLUSION: The results of this experimental investigation show that GKG is a good emulsifying agent even at low concentrations, with many potential applications in the food and pharmaceutical industries. Copyright © 2009 Society of Chemical Industry     

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.     

Emulsion stabilized by starch nanocrystals

The starch nanocrystals made use of in this study were prepared by sulfuric acid hydrolysis of wx maize starch. The stable oil‐in‐water emulsions of 50 vol% paraffin liquid were prepared by using starch nanocrystals as emulsifier when the weight percentage concentration of starch nanocrystal relative to water was above 0.02 wt%. The size of the droplets decreased with the raising of the concentration of starch nanocrystal. These emulsions were very stable to coalescence over months and the creaming of emulsions decreased with the increasing of starch nanocrystal concentration. The surface tension of starch nanocrystal dispersions was found decreased from 71.7 to 45.8 mN/m when the nanocrystal concentration grew from 0.05 to 3.0 wt%. This indicates that starch nanocrystals are surface active particles. Further tests on the emulsifying ability of supernatant of centrifuged starch nanocrystal dispersions and the emulsion stability at the melting temperature of starch nanocrystals confirmed that the emulsions were indeed stabilized by starch nanocrystals.     

Isolation and characterization of Mexican jackfruit (Artocarpus heterophyllus L) seeds starch in two mature stages

Starch was isolated from jackfruit (Artocarpus heterophyllus L) seeds grown in México at different stages of fruit maturity and ripeness. Seeds represent about 8–15% from the fruit that can weigh around 2–36 kg. Proximate composition of seeds showed a high protein content (ca. 22%). Starch yield was 14% with a purity of 81% in both ripeness stages and AM content was lower (12.27%) than other non‐common starch sources. The starch granules in physiological mature (PM) and consumption ripeness (CR) jackfruit showed birefringence with diverse shapes such as semi‐oval or bell shapes. The size of starch granules for PM ranged between 3 and 9.5 µm and for CR between 3 and 12 µm. A‐type XRD pattern was similar to cereal starches. PM starch had higher peak viscosity than CR, but CR did not show breakdown; both starches presented setback during cooling. Thermal properties of gelatinization and retrogradation in PM and CR starches were similar. Characterization performed on this non‐common starch showed that it could be an alternative to use in food systems.     

Gel‐like emulsions prepared with zein nanoparticles produced through phase separation from acetic acid solutions

In this article, we report the microstructure and rheological property of Pickering emulsions stabilised with zein nanoparticles prepared through phase separation from acetic acid solution. The fresh emulsions showed liquid‐like behaviour and reasonable small droplet size. Interestingly, after 3 days of storage at 25° C, the emulsions changed into solid‐like state. The viscosity remarkably increased, and the storage modulus was much larger than the loss modulus. These results indicate the formation of the gel‐like network in emulsions. The droplet size also showed an obvious increase, while the big droplets could be disrupted into small ones in the presence of sodium dodecyl sulphate. The particle network in the continuous phase was seen in the confocal laser scanning microscopy. Therefore, it is suggested that the gel‐like network is formed by the flocculation of oil droplets and particle network in continuous, mainly through the hydrophobic interactions between the particles.     

Pea protein exhibits a novel Pickering stabilization for oil-in-water emulsions at pH 3.0

In this paper we reported that pea protein isolate (PPI) at pH 3.0 exhibits a novel Pickering stabilization for oil-in-water emulsions. At pH 3.0, most of the proteins in PPI were present in the nanoparticle form, with the hydrodynamic diameter of 134–165 nm depending on the concentration (c; 0.25–3.0 g/100 mL). For the emulsions formed at a specific oil fraction of 0.2, increasing the c from 0.25 to 3.0 g/100 mL resulted in a considerable reduction in the emulsion size, while their creaming stability progressively increased, and especially at c values higher than 2 g/100 mL, no creaming occurred even after storage of 20 days. Confocal laser scanning microscopy observations showed that increasing the c resulted in a progressive increase in extent of droplet flocculation, and at higher c values, a network consisting of flocculated droplets could be formed. The emulsions formed at c values above 1.0 g/100 mL exhibited extraordinary stability against coalescence. The flocculated droplet network formation was closely associated with the increased amount of adsorbed proteins at the interface. The results suggest that pea proteins exhibit a good potential to act as a kind of Pickering stabilizers for oil-in-water emulsions at acidic pHs.     

Stability of oil‐in‐water emulsions as influenced by thermal treatment of whey protein dispersions or emulsions

Properties of whey protein concentrate stabilised emulsions were modified by protein and emulsion heat treatment (60–90 °C). All liquid emulsions were flocculated and the particle sizes showed bimodal size distributions. The state and surface properties of proteins and coexisting protein/aggregates in the system strongly determined the stability of heat‐modified whey protein concentrate stabilised emulsions. The whey protein particles of 122–342 nm that formed on protein heating enhanced the stability of highly concentrated emulsions. These particles stabilised protein‐heated emulsions in the way that is typical for Pickering emulsions. The emulsions heated at 80 and 90 °C gelled due to the aggregation of the protein‐coated oil droplets.     

Influence of tragacanth gum exudates from specie of Astragalus gossypinus on rheological and physical properties of whey protein isolate stabilised emulsions

The aim of this work was to investigate the effects of Iranian tragacanth gum (Astragalus gossypinus) (0.5, 1 wt.%), Whey protein isolate (WPI) (2, 4 wt.%) and acid oleic‐phase volume fraction (5, 10% v/v) on droplet size distribution, creaming index and rheological properties of emulsions with various compositions. Rheological investigations showed that both loss and storage modules increased with gum and oil contents. However, the viscoelastic behaviour was mainly governed by the gum concentration. Delta degree (storage and loss modules ratio) increased with frequency indicated that liquid like viscose behaviour dominates over solid like elastic behaviour. The shear‐thinning behaviour of all dispersions was successfully modelled with power law and Ellis models and Ellis model was founded as the better model to describe the flow behaviour of dispersions. Droplet size distribution was measured by light scattering; microscopic observations revealed a flocculated system. Increase in gum, WPI and oil contents resulted in decrease in creaming index of emulsions with dominant effect of gum concentration.     

Impact of High Hydrostatic Pressure on the Emulsifying Properties of Whey Protein Isolate–Chitosan Mixtures

The influence of high hydrostatic pressure (HHP) on the emulsifying properties of whey protein isolate (WPI) and chitosan mixtures in sunflower oil-in-water emulsion has been investigated at pH 4.0. WPI and chitosan mixtures at various ratios were treated at pressure levels in the range of 0–600 MPa for 10–30 min. The emulsifying properties of the mixtures were analyzed by dynamic light scattering and a centrifugal sedimentation technique. HHP treatments of the mixtures resulted in improvement in their emulsifying properties, with the emulsions formed showing more than threefold reductions in droplet size, much more homogeneous droplet distribution, and better creaming stability. The higher the treatment pressure was, the smaller the droplet size and more stable the emulsions were, with those prepared with the mixtures treated at 600 MPa showing no noticeable creaming after 30 days of storage at ambient temperature. The ratio of WPI to chitosan and treatment time also affected the emulsification stability of the mixtures, with a WPI to chitosan ratio of 1:4 (w/w) and treatment time of 20 min found to be the optimum conditions. These results showed that HHP could be a useful method for enhancing the emulsifying properties of protein–polysaccharide mixtures.     

疏水改性藜麦淀粉的制备及其Pickering乳液乳化性研究

本文用碱提法从藜麦种子中提取藜麦淀粉,并用辛烯基琥珀酸酐(Octenyl Succnic Anhydride,OSA)对提取的藜麦淀粉进行疏水改性,得到了辛烯基琥珀酸淀粉酯(OSA淀粉)。通过傅里叶红外光谱、扫描电子显微镜对比原淀粉和OSA淀粉颗粒的结构和形态,发现OSA基团成功接到淀粉表面,在形态上表现为颗粒表面轻度破坏。通过测定乳液微观结构,乳滴粒径及乳化指数(EI),分析了OSA淀粉取代度、颗粒浓度和油相比例等因素对Pickering乳液乳化性的影响。结果表明,乳滴粒径随OSA淀粉取代度或淀粉颗粒浓度的增加而减小、EI值随OSA淀粉取代度或淀粉颗粒浓度的增加而提高,乳液乳化性增强。当油相比例的增加时,乳滴粒径增大,且在食品添加剂允许OSA添加量的范围内,取代度为1.43%的OSA淀粉颗粒的EI值达到最大值75.48%,乳化性最好。研究表明OSA改性藜麦淀粉作为Pickering乳液的稳定颗粒在食品领域有极大的应用潜力。