Interfacial composition and stability of emulsions made with mixtures of commercial sodium caseinate and whey protein concentrate

Controlling release of astaxanthin in β-sitosterol oleogel-based emulsions via different self-assembled mechanisms and composition of the oleogelators

In this study, three types of β-sitosterol-based oleogels (β-sitosterol + γ-oryzanol oleogels, β-sitosterol + lecithin, oleogels and β-sitosterol + monostearate oleogels), loaded with astaxanthin, were employed as the oil phase to create oleogel-based emulsions (SO, SL, and SM) using high-pressure homogenization. The microstructure revealed that fine-scale crystals were dispersed within the oil phase of the droplets in the β-sitosterol oleogel-based emulsion. The bioaccessibility of astaxanthin was found to be 58.13 %, 51.24 %, 36.57 %, and 45.72 % for SM, SL, SO, and the control group, respectively. Interestingly, the release of fatty acids was positively correlated with the availability of astaxanthin (P = 0.981). Further analysis of FFAs release and kinetics indicated that the structural strength of the oil-phase in the emulsions influenced the degree and rate of lipolysis. Additionally, the micellar fraction analysis suggested that the nature and composition of the oleogelators in SM and SL also impacted lipolysis and the bioaccessibility of astaxanthin. Furthermore, interfacial binding of lipase and isothermal titration calorimetry (ITC) measurements revealed that the oleogel network within the oil phase of the emulsion acted as a physical barrier, hindering the interaction between lipase and lipid. Overall, β-sitosterol oleogel-based emulsions offer a versatile platform for delivering hydrophobic molecules, enhancing the bioavailability of active compounds, and achieving sustained release.

Jamming to unjamming: Phase transition in cyclodextrin-based emulsions mediated by sodium casein

HYPOTHESIS

Cyclodextrin (CD) can spontaneously build up the solid particle membrane with CD-oil inclusion complexes (ICs) by a self-assembly process. Sodium casein (SC) is expected to preferentially adsorb at the interface to transform the type of interfacial film. The high-pressure homogenization can increase interfacial contact opportunities of the components, which promote the phase transition of the interfacial film.

EXPERIMENTS

We added SC by sequential and simultaneous orders to mediate the assembly model of the CD-based films, examined the patterns in which the films adopt phase transitions to retard emulsion flocculation, and studied the physic-chemical properties of the emulsions and films from the structural arrest, interface tension, interfacial rheology, linear rheology, and nonlinear viscoelasticities through Fourier transform (FT)-rheology and Lissajous-Bowditch plots.

FINDINGS

The interfacial and large amplitude oscillatory shear (LAOS) rheological results showed that the films changed from jammed to unjammed. We divide the unjammed films into two types: one is SC dominated liquid-like film, which is fragile and related to droplet coalescence; the other is cohesive SC-CD film, which helps droplet rearrangement and retards droplet flocculation. Our results highlight the potential of mediating phase transformation of interfacial films to improve emulsion stability.

Interfacial protein-protein displacement at fluid interfaces

Protein blends are used to stabilise many traditional and emerging emulsion products, resulting in complex, non-equilibrated interfacial structures. The interface composition just after emulsification is dependent on the competitive adsorption between proteins. Over time, non-adsorbed proteins are capable of displacing the initially adsorbed ones. Such rearrangements are important to consider, since the integrity of the interfacial film could be compromised after partial displacement, which may result in the physical destabilisation of emulsions. In the present review, we critically describe various experimental techniques to assess the interfacial composition, properties and mechanisms of protein displacement. The type of information that can be obtained from the different techniques is described, from which we comment on their suitability for displacement studies. Comparative studies between model interfaces and emulsions allow for evaluating the impact of minor components and the different fluid dynamics during interface formation. We extensively discuss available mechanistic physical models that describe interfacial properties and the dynamics of complex mixed systems, with a focus on protein in-plane and bulk-interface interactions. The potential of Brownian dynamic simulations to describe the parameters that govern interfacial displacement is also addressed. This review thus provides ample information for characterising the interfacial properties over time in protein blend-stabilised emulsions, based on both experimental and modelling approaches.

Effects of Proteins and Mineral Ions on the Physicochemical Properties of 1,3-Dioleoyl-2-Palmitoylglycerol Emulsion to Mimic a Liquid Infant Formula

Proteins and minerals in infant formula not only serve as nutrients, but also have important effects on the physical and chemical stability of emulsions. In this study, calcium carbonate (0 or 9.08 mM) and potassium chloride (0 or 15.96 mM), as representatives of divalent and monovalent minerals, were added to 1,3-dioleoyl-2-palmitoylglycerol (OPO) emulsions in different ratios (10:0, 9:1, 6:4, 5:5, and 0:10) of whey protein isolate (WPI) and sodium caseinate (CN). The influence of proteins and minerals on emulsion stability was investigated by analyzing particle size, zeta potential, creaming index, rheological properties, storage stability, and lipid oxidation. 1,3-dioleoyl-2-palmitoylglycerol (OPO) emulsions could be destabilized by adding Ca²⁺, as shown by the increase in particle size index, creaming index, and the decrease in zeta potential magnitude. Divalent ions could affect the electrostatic interactions between lipid droplets and the interactive effects of ion surface adsorption. In addition, the effect of different protein ratios on the physical stability of emulsions was not significant under the same ion-type conditions. In terms of chemical stability, higher oxidized values were found in emulsions stabilized with only CN than in those containing WPI. Our study showed that protein ratios and minerals played an important role in the stability of OPO emulsions, which might provide a reference for the development and utilization of liquid infant formula.

The impact of pH on mechanical properties, storage stability and digestion of alginate-based and soy protein isolate-stabilized emulsion gel beads with encapsulated lycopene

In alginate-based emulsion gels containing protein-coated droplets, pH can influence the gelation mechanism of alginate gels, and the interactions between alginate molecules and protein-coated droplets, and thus properties of emulsion gels. This study investigated the impact of pH 3-7 on the properties (e.g., surface structures of droplets, mechanical properties, storage stability, digestion behavior) of alginate gel beads containing soy protein isolate(SPI)-stabilized oil droplets. Emulsion droplets were SPI-coated droplets at pH 6-7 and alginate/SPI-coated droplets at pH 3-5. Emulsion droplet flocculation only occurred in emulsions at pH 7.0. Emulsion gel beads at pH 3.0 had lower mechanical strength, higher storage stability, faster release of encapsulated lycopene during in-vitro digestion, and higher bioaccesibility of lycopene after 2 h of intestinal digestion than those at pH 7.0 and 5.0. The findings of this study are crucial to emulsion gel beads with controlled release and improved storage stability of encapsulated compounds by changing the pH of emulsions.

Biopolymer Additives Enhance Tangeretin Bioavailability in Emulsion-Based Delivery Systems: An In Vitro and In Vivo Study

The oral bioavailability of tangeretin, a poly(methoxyflavone) found in citrus fruits, is typically very low because of its extremely limited solubility. In this research, tangeretin was encapsulated within whey protein-stabilized emulsions containing ingredients that may alter their behavior under gastrointestinal conditions and enhance the bioavailability of tangeretin after oral administration: cinnamaldehyde (CA), gum arabic (GA), or hydroxypropyl methylcellulose (HPMC). The presence of these ingredients altered the size, aggregation state, and encapsulation efficiency of tangeretin in the emulsions. In vitro studies demonstrated that the bioaccessibility of the encapsulated tangeretin was much higher than that of a crude tangeretin oil suspension. Particularly, the addition of HPMC increased the bioaccessibility of tangeretin from around 36 to 90%. In vivo pharmacokinetics results using rats indicated that tangeretin concentration in the plasma increased from 4- to 20-fold after encapsulation, especially in the presence of HPMC. HPMC also prolonged the release of tangeretin to 22 h. Tangeretin preferentially accumulated within the liver and kidney of the animals. Overall, the knowledge confirmed that structured emulsion-based delivery systems could be used to improve the oral bioavailability of hydrophobic functional ingredients.

The mechanism of improved thermal stability of protein-enriched O/W emulsions by soy protein particles

Growing interest in nutritional and functional foods has motivated the design of protein-enriched products in the food industry, which, however, is greatly challenged by undesirable aggregation and gelation of proteins induced by heating from the pasteurization process. In this study, we reported the preparation of heat-stable soy protein particles (SPPs) by a simple preheating process (100 °C for 30 min) at pH 6.2 and 0.5% (w/v) protein concentration. As a proof of concept, the thermal stability of high-protein emulsions prepared by SPPs compared to native soy proteins (SPs) was investigated. The results showed that high-protein emulsions stabilized by SPPs exhibited appreciable heat stability, whereas SPs gelled when both samples were tested at an identical concentration (10%, w/v). In addition, the emulsions prepared by SPPs demonstrated lower values of storage modulus and viscosity along with a stable size by heat treatment as well as a more stable coated protein layer, in contrast to those prepared by SPs presenting macroscopic aggregation and an unstable coated protein layer. The results would provide valuable information in terms of the development of heat-stable, high-protein, and well-dispersed food emulsions that may find numerous applications in the food industry.

Apparent thermal and UHT stability of native, homogenized and recombined creams with different average fat globule sizes

Milk fat globule size plays a significant role in stability, microstructure and nutritional functionalities of dairy-based products. Understanding of thermal stability of differentiated-size fat globules in dairy creams can provide intervention opportunities for improving functionalities and shelf-life of dairy-based products. This study focused on apparent thermal and UHT stability of native, homogenized (from native cream) and recombined creams (sodium caseinate-stabilized anhydrous milk fat) as a function of their fat globule sizes at 18 and 36% fat contents. Native creams were fractionated by the two-stage centrifugal method into five sizes (~1.45, ~2.45-3.65, ~3.85 and ~4.5 μm) whereas homogenized and recombined creams (~1.45, ~2.45, ~3.85 and ~4.5 μm) were obtained by microfluidisation. All cream samples were tested for thermal stability at 140 °C following a test similar to Heat Coagulation Time. Some selected creams were also studied for UHT stability at 140 °C for 4 s. Native creams exhibited diverse thermal stability depending upon fat content and size; however, native creams (~2.45-3.65 and ~4.5 μm) were UHT stable. Native creams of all sizes were also significantly more thermal stable than homogenized creams. Homogenized creams of all sizes at both fat contents showed poor apparent thermal and UHT stability. It appeared that small fat globules of native creams were more heat stable than larger fat globules at 18% fat content. Recombined creams made with sodium caseinate as emulsifier (without the presence of other milk components) were the most stable among all. However, dilution of recombined cream with skim milk or lactose significantly reduced their apparent thermal stability, but they were UHT stable.

Characterization of physicochemical properties of casein mixture preparation extracted from organic milk for use as an emulsifier in organic processed foods

BACKGROUND

Sodium caseinate (SC) is not considered suitable for use as an emulsifier in organic processed food in the food industry because of the use of prohibited synthetic chemical substances during its production. Casein mixture preparation (CMP), one of the permissible substances specified in the regulations, was isolated from organic milk using citric acid and dibasic potassium phosphate for organic processed foods.

RESULTS

To compare CMP and SC, model emulsions stabilized with each substance were prepared at various concentrations and their physicochemical properties were analyzed. The emulsions' stability was determined using Turbiscan under various environmental stresses. The zeta potential of SC and CPM showed a high surface charge (≤ 30 mV) at all protein concentrations. Because the concentration of the protein preparation increased to 0.75% (w/v), the particle size of the CMP emulsion decreased with the surface load increased as much as that of SC. The CMP and SC emulsions were stable at neutral pH and room temperature. However, at acidic pH and high temperature, both emulsions were destabilized by creaming and flocculation and increased the creaming migration rates.

CONCLUSION

Overall, our data suggest the use of CMP as an emulsifier substitute for SC in organic processed foods. © 2018 Society of Chemical Industry.

Incorporation of bioactive dairy hydrolysate influences the stability and digestion behaviour of milk protein stabilised emulsions

The physical stability of emulsions containing bioactive ingredients is an important aspect of functional food development. This research investigated the effects of a bioactive dairy hydrolysate with anti-inflammatory effects on the properties of oil-in-water emulsions (23% rapeseed oil and 1.5% w/w protein). This was determined by monitoring the effects of various combinations of sodium caseinate (NaCas) and NaCas hydrolysate (NaCasH) (NaCas : NaCasH; 100 : 0, 40 : 60, 30 : 70, 20 : 80 and 0 : 100) on the physico-chemical characteristics (particle size distribution, microstructure, adsorption of protein to the interface, viscosity and creaming stability) of emulsions. Currently, there is growing interest in designing functional foods that modulate lipid digestion. Therefore, emulsion breakdown and subsequent release of free fatty acids (FFAs) from selected NaCasH stabilised emulsions (40 : 60 and 0 : 100) was monitored during in vitro gastrointestinal digestion and compared to the behaviour of emulsions stabilised by NaCas alone. Inclusion of NaCasH generally decreased the stability of the emulsions except when added at a NaCas : NaCasH ratio of 40 : 60 which resulted in emulsions with equivalent stability to the NaCas stabilised emulsions. Although the 40 : 60 combination provided an emulsion system as stable as NaCas, during simulated digestion, these emulsions demonstrated a slower rate of FFA release. This was attributed to the 40 : 60 stabilised emulsions having much larger flocculated lipid droplets than NaCas emulsions, which resulted in reduced surface area and fewer binding sites for lipase adsorption. Accordingly, the 40 : 60 emulsions were hydrolysed more slowly. Emulsions containing only NaCasH exhibited extensive coalescence prior to and during digestion and thus displayed the slowest release of FFA. The results suggest that including NaCasH in the emulsifier blend yields emulsions with modified digestibility and may form the basis of controlling the digestion and release of fat-soluble nutrients in formulated foods. However, further studies are required to optimise the stability of these emulsions before inclusion in such applications.

Triglyceride Structure Modulates Gastrointestinal Digestion Fates of Lipids: A Comparative Study between Typical Edible Oils and Triglycerides Using Fully Designed in Vitro Digestion Model

Three typical edible oils (palm oil, PO; leaf lard oil, LO; rapeseed oil, RO) and triacylglycerols (TAGs) (glycerol tripalmitate, GTP; glycerol tristearate, GTS; glycerol trioleate, GTO) were selected to conduct digestion experiments using fully designed in vitro digestion model. The evolutions in mean particle diameter, ζ-potential, and microstructural changes during different digestion stages were investigated. Free fatty acid (FFA) release extent and kinetics were monitored by pH-Stat method. The particle characterization of different lipids during passage through the GIT depended on lipid type and the microenvironment they encountered. Absorbed surface protein can hardly be the obstacle for pancreas lipase to catalyze lipid hydrolysis after gastric digestion. The maximum FFA release level and apparent rate constant in small intestine digestion stage of the three oils and TAGs were: PO > RO > LO, GTP > GTS > GTO, respectively. PO showed the highest FFA release level and rate mainly due to the short chain length saturated palmitic acid (C16:0) specifically located in the Sn-1, 3 positions of TAG molecules in palm oil, while the Sn-1, 3 positions of TAG molecules in RO and LO were mainly mono- or polyunsaturated fatty acids (C18:1 or C18:2), restricting the continuous hydrolysis reaction. These findings can provide some basic understanding of the digestion differences of different lipids, which may be useful for their nutritional and functional evaluation and the applicability in the food area.

Development of food emulsions containing an advanced performance xanthan gum by microfluidization technique

Gums are often used to increase the viscosity of the continuous phase of oil-in-water emulsions in order to reduce or inhibit some destabilization processes such as creaming. A new type of xanthan gum, advanced performance xanthan gum, which possesses improved rheological properties, has been used as a stabilizer. The addition of advanced performance xanthan gum to egg protein-based emulsions prepared at different homogenization pressures in Microfluidizer was studied. These emulsions showed different droplet size distributions and flocculation degrees. However, all the emulsions studied exhibited the same viscoelastic properties, characterized by a crossover point in the mechanical spectra. This work demonstrates the essential role of this novel gum in the rheology of emulsions. In addition, there is a direct relation between homogenization pressure and flocculation degree. This flocculation led to destabilization by coalescence in these emulsions, being the emulsion processed at the smallest homogenization pressure the most stable.

Microencapsulation of borage oil with blends of milk protein, β-glucan and maltodextrin through spray drying: physicochemical characteristics and stability of the microcapsules

BACKGROUND

Borage oil is a rich commercial source of γ-linolenic acid (18:3n-6). However, borage oil is rich in omega-6 polyunsaturated fatty acids and vulnerable to oxidation. Thus, selecting appropriate wall materials is critical to the encapsulation of borage oil. The present study investigated the influence of wall materials on the physicochemical characteristics and stability of microencapsulated borage oil by spray drying. Blends of milk protein [sodium caseinate (CAS) or whey protein concentrate], β-glucan (GLU) and maltodextrin (MD) were used as the wall materials for encapsulating borage oil.

RESULTS

The microencapsulation of borage oil with different wall materials attained high encapsulation efficiencies. The microencapsulated borage oil prepared with CAS-MD achieved the optimal encapsulation efficiency of 96.62%. The oxidative stabilities of borage oil and microencapsulated borage oil were measured by accelerated storage test at 45 °C and 33% relative humidity for 30 days. The microencapsulated borage oil presented lower peroxide values than those of borage oil, and the microcapsules prepared with CAS-10GLU-MD (consisting of CAS 50 g kg^-1 , GLU 100 g kg^-1 and MD 475 g kg^-1 of microencapsulation) conferred borage oil with high protection against lipid oxidation.

CONCLUSION

The results of the present study demonstrate that the CAS-GLU-MD blend is appropriate for microencapsulating borage oil. © 2017 Society of Chemical Industry.

Comparative Study on Compositions and Functional Properties of Porcine, Chicken and Duck Blood

Hematological, chemical and functional characteristics of porcine, chicken and duck blood were evaluated. A porcine blood sample showed the most abundant red blood cell, hemoglobin concentration, packed cell volume and plasma protein content as well as its freeze-dried blood possessed the highest contents of protein, fat, Cu and Cr with the highest percentage of heme iron (p<0.05). Unlike porcine blood, chicken blood showed a well balance in some essential amino acids, specifically for a higher isoleucine content (p<0.05). Furthermore, it possessed the highest contents of carbohydrate, Zn and non-heme iron (p<0.05). The most rapid response to form a strong gel, especially at 70°C and 80°C, was found in chicken blood, followed by duck and porcine blood, respectively. The result of emulsion activity index (EAI) and emulsion stability index (ESI) at the low protein concentration indicated that chicken blood had the most superior emulsion properties (p<0.05). Regarding duck blood, it exhibited the highest content of Mg and Mn (p<0.05). Moreover, duck blood had similar foaming properties to porcine blood in which they showed higher values than chicken blood (p<0.05). Specific characteristics of blood were therefore diminished by animal species in which this information could be used as food supplementation or product development based on their potential applications.

Impact of the environmental conditions and substrate pre-treatment on whey protein hydrolysis: A review

Proteins in solution are subject to myriad forces stemming from interactions with each other as well as with the solvent media. The role of the environmental conditions, namely pH, temperature, ionic strength remains under-estimated yet it impacts protein conformations and consequently its interaction with, and susceptibility to, the enzyme. Enzymes, being proteins are also amenable to the environmental conditions because they are either activated or denatured depending on the choice of the conditions. Furthermore, enzyme specificity is restricted to a narrow regime of optimal conditions while opportunities outside the optimum conditions remain untapped. In addition, the composition of protein substrate (whether mixed or single purified) have been underestimated in previous studies. In addition, protein pre-treatment methods like heat denaturation prior to hydrolysis is a complex phenomenon whose progression is influenced by the environmental conditions including the presence or absence of sugars like lactose, ionic strength, purity of the protein, and the molecular structure of the mixed proteins particularly presence of free thiol groups. In this review, we revisit protein hydrolysis with a focus on the impact of the hydrolysis environment and show that preference of peptide bonds and/or one protein over another during hydrolysis is driven by the environmental conditions. Likewise, heat-denaturing is a process which is dependent on not only the environment but the presence or absence of other proteins.

Oral processing of emulsion systems from a colloidal perspective

This review discusses recent understanding of the oral destabilization of food emulsions from a colloidal perspective.