Physicochemical properties of whey protein, lactoferrin and Tween 20 stabilised nanoemulsions: Effect of temperature, pH and salt

Design of new lipids from bovine milk fat for baby nutrition

The lipid phase of infant formulas is generally composed of plant-based lipids structured with a high concentration of palmitic acid (C16:0) esterified at the sn-2 position of triacylglycerol since this structure favors the absorption and metabolism of fatty acids. Palm oil is commonly used to make up the lipid phase of infant formulas due to its high concentration of palmitic acid and solids profile and melting point similar to human milk fat. However, the addition of palm oil to infant formulas has been associated with the presence of 3-monochloropropane-1,2-diol (3-MCPD) esters, a group of glycerol-derived chemical contaminants (1,2,3-propanotriol), potentially toxic, formed during the refining process of vegetable oil. Bovine milk fat obtained from the complex biosynthesis in the mammary gland has potential as a technological alternative to replace palm oil and its fractions for the production of structured lipids to be used in infant formulas. Its application as a substitute is due to its composition and structure, which resembles breast milk fat, and essentially to the preferential distribution pattern of palmitic acids (C16:0) with approximately 85% distributed at the sn-1 and sn-2 position of triacylglycerol. This review will address the relationship between the chemical composition and structure of lipids in infant nutrition, as well as the potential of bovine milk fat as a basis for the production of structured lipids in substitution for the lipid phase of vegetable origin currently used in infant formulas.

Milk fat nanoemulsions stabilized by dairy proteins

Droplet size, polydispersity, physical and polymorphic stability of milk fat nanoemulsions produced by hot high-pressure homogenization and stabilized by whey protein isolate (WPI pH 4.0 or 7.0) or sodium caseinate (NaCas pH 7.0) were evaluated for 60 days of storage at 25 °C. Smaller droplets were observed for the NaCas pH 7.0 nanoemulsion, which also showed a lower polydispersity index, resulting in a stable emulsified system for 60 days. On the other hand, the nanoemulsion with bigger droplet size (WPI pH 4.0) showed reduced stability, probably due to the pH near the isoelectric point of the whey proteins. The nanostructured milk fat exhibited the same melting behavior as the bulk milk fat, with a balance between liquid and crystallized fat, and crystals in polymorphic form β'. This could be an advantage concerning the application of the system for delivery of bioactive compounds and improvement of the sensory properties of fat-based food. In summary, nanoemulsions stabilized by NaCas (pH 7.0) showed higher kinetic stability over the storage time, which from a technological application point of view is a very important factor in the food industry.

Ionic strength and pH stability of oil-in-water emulsions prepared with acid-hydrolyzed insoluble proteins from Chlorella protothecoides

BACKGROUND

Chlorella protothecoides is one of the most widely commercialized and studied microalgae species. Recent research reported improved emulsifying properties of the insoluble protein fraction from C. protothecoides after thermal-acid treatment.

RESULTS

In this research, we studied the influence of ionic strength (sodium chloride 50-500 mmol L^-1 or calcium chloride 5-50 m mol L^-1 ) and pH (2-9) on the stability of oil-in-water emulsions prepared by 3% (w/w) of the untreated insoluble microalgae protein fraction or hydrolysates obtained after treatment with hydrochloric acid at 65 °C (Hydrolysates 65) or 85 °C (Hydrolysates 85) for 4 h. The emulsions were prepared by mixing 10% (w/w) oil and homogenized at 68.9 MPa. The ionic strength and pH were, subsequently, adjusted. The mean particle diameter of emulsions remained constant despite extensive variations in ionic strength or pH. Emulsion droplets stabilized by Hydrolysates 85 were stable against coalescence at all ionic strengths or pH values tested.

CONCLUSION

The results indicate a high potential to use acid-hydrolyzed insoluble microalgae protein fractions for the formulation of various emulsion-based food systems. © 2020 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Formation of Taste-Active Pyridinium Betaine Derivatives Is Promoted in Thermally Treated Oil-in-Water Emulsions and Alkaline pH

The oil-water interface can be used as an efficient reaction controller in foods by carrying specific reactants and products in either the hydrophobic or hydrophilic phase. The formation of the taste-active compounds N-(1-carboxyethyl)-6-hydroxymethyl-pyridinium-3-ol inner salt (alapyridaine) and 1-(1-carboxyethyl)-3-hydroxy-pyridinium inner salt is influenced by the presence of a dispersed saturated triglyceride oil phase and by the pH of the aqueous phase. At pH 6.5, the formation of both betaines was 1.24 and 6 times higher in emulsions than in aqueous solution after 4 min at 140 °C. In alkaline emulsions (pH = 9.5, 4 min), the concentrations of alapyridaine and 1-(1-carboxyethyl)-3-hydroxy-pyridinium ion were 6.2 and 3.8 times higher, respectively, than in unbuffered emulsions as a result of the interaction between the polar head group of the surfactant and pyridinium rings. Here, we reported for the first time the effects of multiphase systems on the formation of nonvolatile, taste-active end products.

Influence of Long-Chain/Medium-Chain Triglycerides and Whey Protein/Tween 80 Ratio on the Stability of Phosphatidylserine Emulsions (O/W)

Phosphatidylserine (PS) is a major anionic phospholipid constituent of membrane bilayers, which is specifically enriched in the cytoplasmic leaflet, has functions of regulating the intracellular signaling pathways of neuronal survival and differentiation, and acts as a neurotransmitter to control the activity of neurons. Oil-in-water (O/W) emulsions could improve the bio-availability of PS. Thus, there is a high level of interest in PS emulsion because of its purported health benefits. However, because of high viscosity and poor fluidity, it remains difficult to make the emulsion. A detailed analysis with suited biophysical methods would help to better understand the processes on a molecular level. Therefore, the main aim of the present study was to engineer and characterize a stable O/W phosphatidylserine emulsion. Furthermore, the effect of emulsifiers mixture, whey protein isolate (WPI), and Tween 80 (T80), as well as the oil phase was systematically evaluated. The key parameters were the chain length and the degree of nonsaturation (sunflower oil, a long-chain triglycerides [LCTs] or a medium-chain triglycerides [MCTs]). Small droplets of emulsions could be obtained by adjusting the type of emulsifier and the LCT/MCT ratio. A stable PS emulsion characterized by a smaller droplet size, higher negative zeta-potential, lower centrifugal stability constant, and longer storage time was produced by MCTs T80 (2.0%, w/w) with T80 (2.0%, w/w) as the emulsifier, and by LCTs with the WPI (0.5%, w/w)-T80 (1.5%, w/w) as the emulsifier, respectively. The PS emulsion with LCTs exhibited higher viscosity, when compared to the emulsion made by MCT at the same emulsifier concentration, while all emulsions exhibited a shear thinning behavior. The microstructure images revealed that the PS emulsions produced by MCTs and T80 (2.0%, w/w) or WPIs (0.5%, w/w)-T80 (1.5%, w/w) mixed with LCTs can form specific uniform networks, in order to prevent flocculation. After 28 days of storage, no visual phase separation was observed in the emulsions, except for the PS emulsion with the WPI (2.0%, w/w). It was concluded that the characteristics of the interfacial layer of particles in the PS emulsion system were not only dependent on the proportion of the applied emulsifiers, but also dependent on the oily phase features. These findings may provide indications for choosing the suitable process parameters when a stable PS emulsion is produced.

Dermal Delivery Enhancement of Natural Anti-Ageing Compounds from Ocimum sanctum Linn. Extract by Nanostructured Lipid Carriers

This study aimed to develop nanodelivery systems for enhancing the Ocimum sanctum Linn. extract delivery into the skin. Rosmarinic acid (RA) was used as a marker for the quantitative determination of the extract by high-performance liquid chromatography. Nanostructured lipid carriers (NLC), nanoemulsion, liposome, and niosome, were developed and characterized for internal droplet size, polydispersity index (PDI), and zeta potential using photon correlation spectroscopy. Irritation properties of each formulations were investigated by hen's egg test on the chorioallantoic membrane. In vitro release, skin permeation, and skin retention are determined. NLC was suggested as the most suitable system since it enhances the dermal delivery of RA with the significant skin retention amount of 27.1 ± 1.8% (p < 0.05). Its internal droplet size, PDI, and zeta potential were 261.0 ± 5.3 nm, 0.216 ± 0.042, and -45.4 ± 2.4 mV, respectively. RA released from NLC with a sustained release pattern with the release amount of 1.29 ± 0.15% after 24 h. NLC induced no irritation and did not permeate through the skin. Therefore, NLC containing O. sanctum extract was an attractive dermal delivery system that was safe and enhanced dermal delivery of RA. It was suggested for further used as topical anti-ageing products.

Tween 80 and Soya-Lecithin-Based Food-Grade Nanoemulsions for the Effective Delivery of Vitamin D

Fortification of food and beverages with vitamin D is demanding due to its poor water solubility and oxidation, due to exposure to light and high temperature. The purpose of this research work was to formulate an effective food-grade delivery system for the incorporation of vitamin D into food products and beverages. Food-grade vitamin D nanoemulsions were successfully prepared using mixed surfactant (Tween 80 and soya lecithin) and ultrasonic homogenization techniques. Significant effects (p < 0.05) of temperatures (4 and 25 °C) and storage intervals (1 month) were observed on the turbidity and vitamin D retention. At the end of a 2 month storage, the droplet sizes of the nanoemulsion were 140.15 nm at 4 °C and 155.5 nm at 25 °C. p-Anisidine value of canola oil significantly reduced (p < 0.05) after its incorporation into nanoemulsions. The turbidity values of nanoemulsions increased with the increase in storage duration and temperature. These nanoemulsions remain stable against a wide range of temperatures (30-90 °C), pH values (2-8), ionic strengths (50-400 mM), and freeze-thaw cycles (4 cycles). At the end of 30 days of storage, vitamin D retentions were 74.4 ± 1.2 and 55.3 ± 2.1% in nanoemulsions stored at 4 and 25 °C, respectively. These results suggest that mixed-surfactant-based nanoemulsions are an effective delivery system for the incorporation of vitamin D into food and beverages to overcome the worldwide deficiency of vitamin D.

Dynamic gastric stability and in vitro lipid digestion of whey-protein-stabilised emulsions: Effect of heat treatment

The stability behaviours of whey-protein-stabilised emulsions under gastric conditions and the effects on the lipolysis of the emulsions were investigated using an in vitro dynamic human gastric simulator and a subsequent small intestinal model. Under gastric conditions, heated whey-protein-stabilised emulsions flocculated to a greater extent and with a larger floc size, whereas unheated emulsions were more prone to coalescence. The greater extent of flocculation delayed the delivery of oil droplets to the small intestine, leading to a lower amount of oil in the emptied gastric digesta from the heated emulsion in the early period of digestion. The differences in oil content, droplet size and interfacial composition led to a greater rate and extent of lipolysis in the subsequent intestinal digestion in the heated emulsion than the unheated emulsion. The results suggest that the lipid digestion of whey-protein-stabilised emulsions in the intestinal stage could be manipulated by thermal treatment.

Factors impacting lipid digestion and β-carotene bioaccessibility assessed by standardized gastrointestinal model (INFOGEST): oil droplet concentration

The impact of oil droplet concentration on lipid digestion and vitamin bioaccessibility was measured using the INFOGEST method.

Chitosan dispersed in aqueous solutions of acetic, glycolic, propionic or lactic acid as a thickener/stabilizer agent of O/W emulsions produced by ultrasonic homogenization

Chitosan is a natural polycationic polysaccharide with several known biotechnological functionalities, but its application in food products as ingredient or additive remains nowadays unusual. Additionally, ultrasonic production of food-grade emulsions is still an open research field, so ultrasound applicability for such purpose must be evaluated case by case. In this study, chitosan was dispersed in acid aqueous media containing acetic, glycolic, propionic or lactic acid (50 mmol·L^-1), then added of the emulsifier Tween 20, and finally mixed to sunflower oil, through ultrasonic homogenization (20 kHz, 500 W, 4 min), in order to prepare O/W emulsions (oil fraction = 0.25). In all studied systems, oil droplets with average hydrodynamic diameter < 600 nm were obtained. The increase of chitosan concentration promoted the augment in consistency and the elastic character of the emulsions. Emulsions containing more than 0.500 g·(100 g)^-1 of chitosan presented a minor increase of both oil droplets average hydrodynamic diameter and PDI, during storage for 28 days. Furthermore, such systems showed no phase separation when exposed to centrifugation, freeze-thawing, and freeze-thaw-heating cycles. Two main findings may be highlighted from this study: i) ultrasound processing is a promising approach to produce food-grade emulsified systems containing chitosan, and ii) chitosan is a suitable alternative as thickener/stabilizer for acidic emulsions, being its performance influenced by the biopolymer concentration and not by the organic acid present in the medium.

Effects of different ionic strengths on the physicochemical properties of plant and animal proteins-stabilized emulsions fabricated using ultrasound emulsification

In this study, high intensity ultrasound (HIU) was used to produce food protein stabilized emulsions under different ionic strengths (0, 25, 50, 100, 200 and 300 mM NaCl). Five plant and animal food proteins, whey protein isolate (WPI), soy protein isolate (SPI), bovine gelatin, peanut protein isolate (PPI) and corn zein were selected as protein emulsifiers. PPI and zein could not form emulsions using ultrasound emulsification at all ionic strengths (from 0 to 300 mM NaCl). However, ultrasound could induce stable emulsions using SPI, WPI and gelatin as emulsifiers. Moreover, different ionic strengths and protein types influenced the physicochemical properties of HIU induced emulsions obviously. It was found that the droplet sizes of gelatin emulsions were lower than those of SPI and WPI emulsions at salt concentrations of 300 mM NaCl. Furthermore, gelatin emulsions had better stability against environmental stresses (salt and temperature) than that of SPI and WPI emulsions. Moreover, the adsorbed protein (%) at the oil/water interface of SPI emulsions was higher than those of WPI and gelatin emulsions. However, the adsorbed protein amount of all proteins stabilized emulsions increased significantly after salt addition. The absolute ζ-potential values decreased with the increase of salt concentrations. The microrheology results indicated that the SPI emulsions formed a gel-like structure at high salt concentrations (>50 mM NaCl) as SPI emulsions exhibited higher elasticity than WPI and gelatin emulsions. In conclusion, the ultrasound as a green emulsification technique could be used to fabricate emulsions stabilized by plant and animal proteins.

Time effect on structural and functional properties of whey protein isolate-gum acacia conjugates prepared via Maillard reaction

BACKGROUND

The functional properties of whey protein isolate (WPI) are sensitive to pH, ionic strength, and temperature. This prevents its application in various food systems and processing technologies. The conjugation of proteins with polysaccharides via the Maillard reaction is an efficient method to improve the functionality of proteins. The purpose of this work was to conjugate gum acacia (GA) with WPI via the dry-heating Maillard reaction and to investigate the effect of reaction time on the physicochemical and functional properties of WPI-GA conjugates.

RESULTS

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and high-performance size exclusion chromatography confirmed the formation of higher molecular weight conjugates. The degrees of glycation for WPI-GA conjugates incubated for 1, 3, 5, and 7 days were 28.14%, 44.98%, 49.50%, and 51.20%, respectively. The glycation reaction reduced the surface hydrophobicity and fluorescence intensity of WPI significantly (P < 0.05). Functional properties of the conjugates, such as solubility, stability against heat-induced insolubility, and emulsion properties were all superior to the control WPI. However, a reaction time longer than a day resulted in a high degree of browning and decreased the functionality of the conjugate significantly (P < 0.05).

CONCLUSION

The results indicated that conjugation of WPI with GA can be a promising way to enhance its functional properties. However, the reaction time suitable for producing conjugates with superior functional properties was not necessarily the highest glycation degree that could be reached. © 2019 Society of Chemical Industry.

Effect of isoelectric point on cheese whey wastewater treatment using a microbial electrochemical system

In this study, a microbial electrochemical system (MES) was employed to investigate the effect of isoelectric point (IEP) on cheese whey wastewater treatment. The experiments were carried out in a bioreactor equipped with a semicircular carbon cloth and stainless steel electrodes as anode and cathode, respectively. The effects of IEP, whey protein concentration, electrical current, and time were studied. The IEP of the whey protein was determined at pH 5.9. The optimum electrical current was obtained at 6 mA for synthetic cheese whey wastewater. The results of rotary exponential doping showed that the third structure of proteins chenges to the second structure at the IEP. The highest protein removal (98%) was obtained at pH 6. The results showed that 76%, 83%, and 98% protein removal were achieved at 2, 4, and 8 h, respectively.

Dual-Targeted Lactoferrin Shell-Oily Core Nanocapsules for Synergistic Targeted/Herbal Therapy of Hepatocellular Carcinoma

Herein, both strategies of synergistic drug combination together with dual active tumor targeting were combined for effective therapy of hepatocellular carcinoma (HCC). Therefore, based on the tumor sensitizing action, the herbal quercetin (QRC) was co-delivered with the targeted therapeutic drug sorafenib (SFB), preformulated as phospholipid complex, via protein shell-oily core nanocapsules (NCs). Inspired by the targeting action of lactoferrin (LF) via binding to LF receptors overexpressed by HCC cells, LF shell was electrostatically deposited onto the drug-loaded oily core to elaborate LF shell-oily core NCs. For dual tumor targeting, lactobionic acid (LA) or glycyrrhetinic acid (GA) was individually coupled to LF shell for binding to asialoglycoprotein and GA receptors on liver cancer cells, respectively. Compared to LF and GA/LF NCs, the dual-targeted LA/LF-NCs showed higher internalization into HepG2 cells with 2-fold reduction in half-maximal inhibitory concentration compared to free combination therapy after 48 h. Moreover, dual-targeted LF-NCs showed powerful in vivo antitumor efficacy. It was revealed as significant downregulation of the mRNA expression levels of nuclear factor-kappa B and tumor necrosis factor α as well as suppression of Ki-67 protein expression level in diethylnitrosamine (DEN)-induced HCC mice (P < 0.05). Furthermore, dual-targeted LF-NCs attenuated the liver toxicity induced by DEN in animal models. Overall, this study proposes dual-targeted LF-NCs for combined delivery of SFB and QRC as a potential therapeutic HCC strategy.

Lipo-Dipeptide as an Emulsifier: Performance and Possible Mechanism

A lipo-dipeptide (C₁₃-lysine-arginine, C₁₃-KR) was designed as a potential emulsifier with good emulsifying properties under acidic condition. Compared with two traditional emulsifiers (whey protein isolate and Tween 80), C₁₃-KR emulsion had the minimum mean size but the highest zeta potential (around +100 mV). Moreover, C₁₃-KR emulsion showed better stability against environmental stresses, such as high salt concentrations and high temperature. The C₁₃-KR particles had the fastest move rate around 400 Hz when it attained an equilibrium state. Furthermore, C₁₃-KR emulsifier could sharply reduce the interfacial tension and had the lowest tension value at the oil/water interface. The interfacial tension of C₁₃-KR emulsifier was only 3.6 mN/m (0.5% w/v). In conclusion, the lipo-dipeptide C₁₃-KR could be considered as an emulsifier to produce emulsion under acidic condition.

Physical and chemical stability of β-carotene nanoemulsions during storage and thermal process

Nanotechnology has become an option for the encapsulation of compounds, such as carotenoids. However, for the incorporation in to food, it is necessary to develop nanometric systems that are stable under the different conditions to which the food is submitted during its production, transport, and storage. Thus, with the intent to develop a stable nanoemulsion formulation for food application, the physical and chemical stability of β-carotene nanoemulsions after thermal treatments and storage under different conditions, were investigated in this work. The β-carotene nanoemulsions were formulated with corn oil, by applying high-pressure homogenization, with an average size in the 300 nm range, which is within the appropriate scale for industrial preparations, such as foods and cosmetics. The nanoemulsion droplets had negative charge (more than -25 mV) and monodisperse profile. The sample were pasteurized, sterilized, and stored at 4, 25, and 37 °C in the presence and absence of light for up to 90 days. Following the heat treatments and storage, the nanoemulsions showed no evidence of physical destabilization, retaining 70-80% of the carotenoid after the pasteurization and sterilization processes, and 70% when stored at 4 °C without light, respectively. Overall, our findings provide new information about the physical and chemical stability of β-carotene nanoemulsions during traditional thermal processes and environmental conditions.

Vitamin E Encapsulation within Oil-in-Water Emulsions: Impact of Emulsifier Type on Physicochemical Stability and Bioaccessibility

The influence of plant-based (gum arabic and quillaja saponin) and animal-based (whey protein isolate, WPI) emulsifiers on the production and stability of vitamin E-fortified emulsions was investigated. Their impact on lipid digestibility and vitamin bioaccessibility was also studied utilizing an in vitro gastrointestinal tract. WPI and saponin produced smaller emulsions than gum arabic. All emulsions had good storage stability at room temperature (4 weeks, pH 7). Saponin- and gum arabic-emulsions were resistant to droplet aggregation from pH 2 to 8 because these emulsifiers generated strong electrosteric repulsion. WPI-coated droplets flocculated around pH 5 due to a reduction in charge near their isoelectric point. Lipid digestion was slower in saponin-emulsions, presumably because the high surface activity of saponins inhibited their removal by bile acids and lipase. Vitamin bioaccessibility was higher in WPI- than in saponin- or gum arabic-emulsions. This information may facilitate the design of more efficacious vitamin-fortified delivery systems.

Stability and in vitro digestibility of beta-carotene in nanoemulsions fabricated with different carrier oils

Beta-carotene, the main dietary source of provitamin A, is required for maintaining optimum human health. The bioaccessibility of beta-carotene can be greatly improved when ingested with fat. Therefore, the aim of the current study was to select proper oils (palm oil, coconut oil, fish oil, and corn oil) as a carrier to form stable nanoemulsion that can effectively enhance the bioaccessibility of beta-carotene. The nanoemulsion was formulated with 90% (v/v) aqueous solution (2% whey protein isolate, WPI, w/v) and 10% (v/v) dispersed oil. The in vitro digestion experiment of nanoemulsions showed that the bioaccessibility of beta-carotene was as followed in order: palm oil = corn oil > fish oil > coconut oil (p < 0.05). The particle size of the nanoemulsion (initial particle size = 168-185 nm) was below 200 nm during 42 days' storage at 25°C. The retention rates of beta-carotene in nanoemulsions were 69.36%, 63.81%, 49.58%, and 54.91% with palm oil, coconut oil, fish oil, and corn oil, respectively. However, the particle size of the nanoemulsion increased significantly in the accelerated experiment at 55°C (p < 0.05), in which the retention rates of beta-carotene were 48.56%, 43.41%, 29.35%, and 33.60% with palm oil, coconut oil, fish oil, and corn oil, respectively. From above, we conclude that WPI-stabilized beta-carotene nanoemulsion with palm oil as the carrier is the most suitable system to increase bioaccessibility and stability of lipid-soluble bioactive compounds such as beta-carotene.

Lactoferrin-tagged quantum dots-based theranostic nanocapsules for combined COX-2 inhibitor/herbal therapy of breast cancer

Aim: Herein, tumor-targeted quantum dots (QDs)-based theranostic nanocapsules (NCs) coloaded with celecoxib and honokiol were developed. Materials & methodology: The anionic CD44-targeting chondroitin sulfate and cationic low density lipoprotein (LDL)-targeting lactoferrin (LF) were sequentially assembled onto the surface of the positively charged oily core. As an imaging probe, highly fluorescent mercaptopropionic acid-capped cadmium telluride QDs were coupled to LF. Results: In vitro, fluorescence of QDs was quenched (OFF state) due to combined electron/energy transfer-mediated processes involving LF. After intracellular uptake of NCs, fluorescence was restored (ON state), thus enabled tracing their internalization. The NCs demonstrated enhanced cytotoxicity against breast cancer cells as well as superior in vivo antitumor efficacy. Conclusion: We propose these multifunctional nanotheranostics for imaging and targeted therapy of breast cancer.

Beverage Emulsions: Key Aspects of Their Formulation and Physicochemical Stability

In the last few decades, lifestyle changes and the awareness of the importance of a balanced diet have led the population to increase the consumption of beverages based on fruit juices and/or vegetables. Fruit and vegetables contain health-related compounds that can impact on physiological processes, thus reducing the risk of certain diseases and improving the overall health status. Consumer demand for more appealing and tasting beverages has also increased. In this sense, fortification of beverages with health-related ingredients and/or flavors arises as a potential strategy for the development of new beverage-based products. Nevertheless, most of those compounds are not soluble in water, thus their incorporation in aqueous food systems, such as beverages, requires an emulsification step. Beverage emulsions are concentrated emulsified systems designed to be further diluted and/or incorporated in beverages and drinks as carriers of water insoluble ingredients. This review article aims at discussing the main key aspects of beverage emulsion formulation and their colloidal stability after being added to complex food systems.

Effect of pH-shifting treatment on structural and functional properties of whey protein isolate and its interaction with (-)-epigallocatechin-3-gallate

Effect of pH-shifting on structural and functional properties of whey protein isolate and its interaction with (-)-epigallocatechin-3-gallate were investigated. Circular dichroism spectra showed that pH-shifting induced the decrease in α-helix content by 12.18% and β-sheet content by 3.24%, but β-turn and random coil content increased by 4.26% and 5.91%, respectively. Increase of fluorescence intensity and red-shift of maximum emission wavelength indicated the structural unfolding and exposure of tyrosine. The treatment also significantly increased the surface hydrophobicity, disulfide bonds content, solubility, emulsifying activity and emulsion stability of whey protein isolate at P < 0.05 level. Fluorescence quenching analysis revealed that treated whey protein isolate have a stronger binding affinity to (-)-epigallocatechin-3-gallate, resulting a better protection against the degradation of (-)-epigallocatechin-3-gallate and its antioxidant activity. This study confirmed that pH-shifting treatment can improve functional properties of whey protein isolate and its potential as a protective carrier for polyphones.

Long-Term Stability of n-Alkane-in-Water Pickering Nanoemulsions: Effect of Aqueous Solubility of Droplet Phase on Ostwald Ripening

High-pressure microfluidization is used to prepare a series of oil-in-water Pickering nanoemulsions using sterically-stabilized diblock copolymer nanoparticles as the Pickering emulsifier. The droplet phase comprised either n-octane, n-decane, n-dodecane, or n-tetradecane. This series of oils enabled the effect of aqueous solubility on Ostwald ripening to be studied, which is the primary instability mechanism for such nanoemulsions. Analytical centrifugation (LUMiSizer instrument) was used to evaluate the long-term stability of these Pickering nanoemulsions over time scales of weeks/months. This technique enables convenient quantification of the fraction of growing oil droplets and confirmed that using n-octane (aqueous solubility = 0.66 mg dm^-3 at 20 °C) leads to instability even over relatively short time periods. However, using n-tetradecane (aqueous solubility = 0.386 μg dm^-3 at 20 °C) leads to significantly improved long-term stability with respect to Ostwald ripening, with all droplets remaining below 1 μm diameter after 6 weeks storage at 20 °C. In the case of n-dodecane, the long-term stability of these new copolymer-stabilized Pickering nanoemulsions is significantly better than the silica-stabilized Pickering nanoemulsions reported in the literature by Persson et al. ( Colloids Surf., A, 2014, 459, 48-57). This is attributed to a much greater interfacial yield stress for the former system, as recently described in the literature (see P. J. Betramo et al. Proc. Natl. Acad. Sci. U.S.A., 2017, 114, 10373-10378).

Gypenosides as natural emulsifiers for oil-in-water nanoemulsions loaded with astaxanthin: Insights of formulation, stability and release properties

The formulation, physicochemical stability and bioaccessibility of astaxanthin (AST) loaded oil-in-water nanoemulsions fabricated using gypenosides (GPs) as natural emulsifiers was investigated and compared with a synthetic emulsifier (Tween 20) that is commonly applied in food industry. GPs were capable of producing nanoemulsions with a small volume mean diameter (d_4,3 = 125 ± 2 nm), which was similar to those prepared using Tween 20 (d_4,3 = 145 ± 6 nm) under the same high-pressure homogenization conditions. GPs-stabilized nanoemulsions were stable against droplet growth over a range of pH (6-8) and thermal treatments (60-120 °C). Conversely, instability occurred under acidic (pH 3-5) and high ionic strength (25-100 mM CaCl₂) conditions. In comparison with Tween 20, GPs were more effective at inhibiting AST from degradation during 30 days of storage at both 5 and 25 °C. However, GPs led to lower lipid digestion and AST bioaccessibility from nanoemulsions than did Tween 20.

Effect of production parameters and stress conditions on beta-carotene-loaded lipid particles produced with palm stearin and whey protein isolate

Abstract Microencapsulation is currently used by the food industry for different purposes, including the protection of ingredients against factors such as oxidation and volatilization, as well as to increase the bioavailability and bioaccessibility of nutrients. The current study aimed to encapsulate beta-carotene in solid lipid microparticles stabilized with whey protein isolate (WPI), and also investigate their integrity during storage and under stress conditions such as different ionic strengths, sucrose concentrations and thermal treatments. Solid lipid microparticles were produced using palm stearin, a food grade vegetable fat, using a single-step high shear process. Of the different formulations used for lipid microparticle production, characterization studies showed that the greatest stability was obtained with systems produced using 1.25% (w/v) whey protein isolate, 5% (w/v) palm stearin and 0.2% (w/v) xanthan gum. This formulation was applied for the production of beta-carotene-loaded solid lipid microparticles, with different concentrations of alpha-tocopherol, in order to verify its possible antioxidant activity. The results showed that the addition of alpha-tocopherol to the dispersions provided an increase in encapsulation efficiency after 40 days of storage that ranged from 29.4% to 30.8% when compared to the system without it. Furthermore, the solid lipid microparticles remained stable even when submitted to high ionic strength and to heating in the proposed temperature range (40 °C to 80 °C), highlighting their feasible application under typical food processing conditions.

Formation of shelf stable Pickering high internal phase emulsions (HIPE) through the inclusion of whey protein microgels

High internal phase emulsions (HIPE) prepared using whey protein microgels (WPMs) as a surfactant were demonstrated to have substantially higher stability than HIPEs prepared using similar loadings of non-gelled whey protein isolate (WPI) or Tween 20.