Phosphatidylcholine-depleted (PC-depleted) lecithin is characterized by a lower phosphatidylcholine/phosphatidylethanolamine (PC/PE) ratio, favoring the formation of water-in-oil (W/O) emulsions, and ...thus can be applied in water-in-oil-in-water (W/O/W) double emulsions (DEs). However, up to now, only a limited number of studies have described the use of PC-depleted lecithin in double emulsions. In this study, the influence of the formulation and processing conditions on the formation and stability of PC-depleted lecithin stabilized-DEs was investigated. The characterizations of DEs involved morphology, droplet size, viscosity, and entrapped water yield. The experimental results indicated that the incorporation of glucose in the water phase instead of potassium chloride (KCl) increased both the droplet size and the entrapped water yield in DEs, whereby the latter was increased by around 65% as compared to DEs containing 100 mM KCl. Reducing the salt content also facilitated the formation of DEs. Moreover, a correlation between the oil type and the 1st homogenization method was found: whereas DEs formulated with high oleic sunflower oil were always unstable irrespective of the emulsification method used, stable DEs were produced by the combination of medium-chain triglyceride oil and a rotor-stator system whereby microfluidization caused phase inversion. In addition, PC-depleted lecithin could stabilize up to 60% of water in oil. Meanwhile, stable DEs with a maximum internal water fraction of 24.1% were obtained by adjusting the original W/O/W ratio to 25/25/50. Finally, DEs stabilized by PC-depleted lecithin showed a comparable stability to those stabilized by polyglycerol polyricinoleate (PGPR) during 28 days of storage. To sum up, this work provides a better understanding of the sensitivity of PC-depleted lecithin-stabilized W/O/W emulsions towards the applied formulation conditions.
•The sensitivity of PC-depleted lecithin to stabilize W/O/W emulsions was analyzed.•Reducing salt content or using glucose instead improved emulsion stability.•Oil type and homogenization method co-regulated emulsion formation and stability.•PC-depleted lecithin stabilized up to 60% water in W/O emulsions.•PC-depleted lecithin yielded W/O/W emulsions with comparable stability to PGPR.
Dry heat conjugation of whey protein has been shown before to improve its heat stabilizing properties when applied as an emulsifier. However, the range of feasible heating conditions of these ...conjugates has not yet been evaluated. Microrheology, a non-destructive method, was utilized in this study to determine the acceptable heating range for whey protein stabilized-emulsions. Practically, oil-in-water emulsions stabilized by whey protein-lactose conjugates were subjected to either an in-situ thermal treatment, including a heating-cooling cycle, or to an isothermal period. The observed microstructural rearrangements were also confirmed by examining the bulk emulsion behavior through oscillatory rheology.
The obtained results indicated that microrheology could unravel the range of heating temperatures and durations for emulsions stabilized by whey protein concentrate (WPC) that was dry heated for 8 and 48 h as compared to the native WPC. The improved heat stability was a result of the conjugates’ ability to prevent the formation of an oil droplet network. Consequently, the conjugated WPC-stabilized emulsions remained mainly viscous with a low elasticity index (EI) and macroscopic viscosity index (MVI) during heating. Furthermore, the microrheology findings were found to be largely in line with bulk rheological properties: both methods indicated a comparable temperature for the onset of network formation upon applying a temperature sweep. The insights from this study may help to stimulate the industrial application of whey protein-sugar conjugates as heat stable natural emulsifiers.
Display omitted
•Microrheology well determine the initial heat-induced destabilization of emulsion.•Whey protein conjugates maintain emulsion microstructure during thermal treatment.•Conjugates-stabilized emulsion has a wide feasible heating range.•Microrheology findings were largely in line with the bulk rheological properties.
In a previous study, biogenic silver nanoparticles were produced by
Lactobacillus fermentum
which served as a matrix preventing aggregation. In this study the antibacterial activity of this biogenic ...silver was compared to ionic silver and chemically produced nanosilver. The minimal inhibitory concentration (MIC) was tested on Gram-positive and Gram-negative bacteria and was comparable for biogenic silver and ionic silver ranging from 12.5 to 50 mg/L. In contrast, chemically produced nanosilver had a much higher MIC of at least 500 mg/L, due to aggregation upon application. The minimal bactericidal concentration (MBC) in drinking water varied from 0.1 to 0.5 mg/L for biogenic silver and ionic silver, but for chemically produced nanosilver concentrations, up to 12.5 mg/L was needed. The presence of salts and organic matter decreased the antimicrobial activity of all types of silver resulting in a higher MBC and a slower inactivation of the bacteria. The mode of action of biogenic silver was mainly attributed to the release of silver ions due to the high concentration of free silver ions measured and the resemblance in performance between biogenic silver and ionic silver. Radical formation by biogenic silver and direct contact were found to contribute little to the antibacterial activity. In conclusion, biogenic nanosilver exhibited equal antimicrobial activity compared to ionic silver and can be a valuable alternative for chemically produced nanosilver.
It has already been hypothesized and in some cases proven that gelation of the internal water droplets of W/O/W-type double emulsions might allow the application of a higher shear in the second ...emulsification step while maintaining a high internal water content. In this contribution, thermal denaturation of a concentrated whey protein isolate solution, which is used as the internal water phase, was investigated. Low-resolution NMR T2-relaxometry measurements (using a CPMG-sequence) clearly showed that this thermal treatment effectively gelled the internal water phase. Using this approach, double emulsion droplets with a small average diameter (D43 of about 5 μm) and narrow particle size distribution were produced while a high internal water content was maintained. Moreover, our results indicated that gelation could not prevent osmotic shrinking of the double emulsion droplets upon dilution in hypertonic solution. However, gelation of the internal water phase clearly reduced the degree of osmotic swelling of the double emulsion droplets upon hypotonic dilution. However, this effect is probably due to droplet-globule coalescence occurring at lower internal water volume increases in case the internal water phase is gelled.
Display omitted
•Internal aqueous phase gelation was proven using low-resolution NMR T2-relaxometry.•W/O/W-droplets with small diameter and high internal water content were produced.•Internal water phase gelation reduced shear-sensitivity of the double emulsion.•Internal water phase gelation influenced osmotic behavior of the double emulsion.
To control and enhance protein functionality is a major challenge for food scientists. In this context, research on food protein fibril formation, especially amyloid fibril formation, holds much ...promise. We here first provide a concise overview of conditions, which affect amyloid formation in food proteins. Particular attention is directed towards amyloid core regions because these sequences promote ordered aggregation. Better understanding of this process will be key to tailor the fibril formation process. Especially seeding, that is, adding preformed protein fibrils to protein solutions to accelerate fibril formation holds promise to tailor aggregation and fibril techno‐functionality. Some studies have already indicated that food protein fibrillation indeed improves their techno‐functionality. However, much more research is necessary to establish whether protein fibrils are useful in complex food systems and whether and to what extent they resist food processing unit operations. In this review the effect of amyloid formation on gelation, interfacial properties, foaming, and emulsification is discussed. Despite their prevalent role as functional structures, amyloids also receive a lot of attention due to their association with protein deposition diseases, prompting us to thoroughly investigate the potential health impact of amyloid‐like aggregates in food. A literature review on the effect of the different stages of the human digestive process on amyloid toxicity leads us to conclude that food‐derived amyloid fibrils (even those with potential pathogenic properties) very likely have minimal impact on human health. Nevertheless, prior to wide‐spread application of the technology, it is highly advisable to further verify the lack of toxicity of food‐derived amyloid fibrils.
Cerium dioxide nanoparticles (CeO2 NPs) are increasingly being used as a catalyst in the automotive industry. Consequently, increasing amounts of CeO2 NPs are expected to enter the environment where ...their fate in and potential impacts are unknown. In this paper we describe the fate and effects of CeO2 NPs of three different sizes (14, 20, and 29 nm) in aquatic toxicity tests. In each standard test medium (pH 7.4) the CeO2 nanoparticles aggregated (mean aggregate size approximately 400 nm). Four test organisms covering three different trophic levels were investigated, i.e., the unicellular green alga Pseudokirchneriella subcapitata, two crustaceans: Daphnia magna and Thamnocephalus platyurus, and embryos of Danio rerio. No acute toxicity was observed for the two crustaceans and D. rerio embryos, up to test concentrations of 1000, 5000, and 200 mg/L, respectively. In contrast, significant chronic toxicity to P. subcapitata with 10% effect concentrations (EC10s) between 2.6 and 5.4 mg/L was observed. Food shortage resulted in chronic toxicity to D. magna, for wich EC10s of > or = 8.8 and < or = 20.0 mg/L were established. Chronic toxicity was found to increase with decreasing nominal particle diameter and the difference in toxicity could be explained by the difference in surface area. Using the data set, PNEC(aquatic)S > or = 0.052 and < or = 0.108 mg/L were derived. Further experiments were performed to explain the observed toxicity to the most sensitive organism, i.e., P. subcapitata. Toxicity could not be related to a direct effect of dissolved Ce or CeO2 NP uptake or adsorption, nor to an indirect effect of nutrient depletion (by sorption to NPs) or physical light restriction (through shading by the NPs). However, observed clustering of NPs around algal cells may locally cause a direct or indirect effect.
Display omitted
•Re-assembled casein micelles were prepared from native caseins by adding different amounts of salts.•The particle size and micellar yield (>85 %) increased with adding salts.•The ...uptake of caseins into the recombined micelles followed the sequence of αs-CN > β-CN > κ-CN.•Calcium ions acted as cross-linkers and participated in the construction of calcium phosphate nanoclusters.•The rennetability was primarily dependent upon the colloidal Ca per g micellar casein.
Inducing the spontaneous aggregation from casein molecules (i.e. αs1, αs2, β, and κ-casein) into re-assembled casein micelles (RCMs) through the addition of salts as an alternative to native casein micelles, has garnered increasing attention in recent years. In this investigation, re-assembled casein micelles were generated by adding varying amounts of calcium, phosphate, and citrate ions to a sodium caseinate dispersion. The formed micelles were further characterized in terms of particle size, optical density, and partitioning of calcium ions and caseins. Besides, their small-angle X-ray scattering (SAXS) profiles and renneting properties were evaluated. The observations revealed that the particle size and optical density of RCMs increased with the continuous addition of salts, while the micellar yield improved and could exceed 85 %. Moreover, the quantity of individual casein molecules that contributed to the creation of micelles was in concordance with their level of phosphorylation (i.e. αs2-casein > αs1-casein > β-casein > κ-casein). Mineral analysis results and SAXS scattering profiles confirmed that the added calcium ions acted as cross-linkers and participated in the construction of calcium phosphate nanoclusters. The renneting ability of RCMs was primarily dependent upon the colloidal calcium content per gram of micellar casein.
The influence of unsaturated (rich in oleic acid, MAG-O) and saturated (rich in stearic acid, MAG-S) monoacylglycerols on the shear-induced partial coalescence and on the whipping properties of ...recombined cream was studied at different concentrations. MAG-O reduces the churning time and the whipping time, lowers the overrun and serum loss and increases the firmness of the whipped cream. The exact opposite effects were observed upon the addition of MAG-S. Protein load analyses, interfacial tension measurements and interfacial rheology experiments were carried out to elucidate the mechanism behind the diverging effects of these monoacylglycerols. The long-chain saturated MAGs behaved as a solid at the oil–water interface while its unsaturated counterpart appeared to be in the liquid state. The occurrence of chain crystallization and subsequent interfacial heterogeneous nucleation appeared to play a decisive role in the stability of RCs towards partial coalescence.
► Clear effect saturation degree monoacylglycerols on partial coalescence ► Link between shear-induced partial coalescence and whipping properties ► Interfacial properties are characterized to support mechanistic model. ► Chain crystallization and subsequent heterogeneous nucleation play decisive role.
In this study, the functionality of colloidal cinnamon nanoparticles in improving the antioxidant activity and suspension stability of a chocolate beverage formulated with two types of cocoa powder ...(natural and alkalised) was investigated. Cinnamon-loaded nanoparticles based on shellac and xanthan gum prepared using anti-solvent precipitation were incorporated in the chocolate beverage in multilevel proportions. The results showed that the addition of the nanoparticles improved the total phenolic content up to 40% and antioxidant activity up to 60% depending on the level of the nanoparticles added. Improvement of the physical stability of the chocolate beverage was observed regardless of the cocoa powder type. As the sedimentation index of the beverages made with alkalised and natural cocoa powders after 96 h was 5.7 and 85.7, respectively, the stabilisation effect of the nanoparticles seemed to be significantly influenced by the characteristics of the beverage raw material. The prevention of cocoa particle sedimentation was attributed to the colloidal network that originated from xanthan gum as shown by Cryo-SEM imaging or the increased viscosity of the mixture (i.e. from 2.4 to 27.7 mPa s at a shear rate of 50 s
−1
). Incorporation of the colloidal cinnamon nanoparticles had no significant effect on pH and a slight effect on the colour of the chocolate beverages. The formulated nanoparticles could be a promising complement to “ready-to-drink” products to enrich the bioactive content and prolong suspension stability.
PDF
