Stability Of Food Emulsions Research Articles

Regenerated silk fibroin for the stabilization of fish oil-loaded Pickering emulsions

Protein nanofibril-stabilized Pickering emulsion is a promising emulsion in the field of food emulsion. However, no microscale protein fibrils have been applied as emulsifiers for the stabilization of food emulsions. In this work, regenerated silk fibroin (RSF) was prepared and applied to stabilize fish oil-loaded Pickering emulsions. RSF could form a microfiber-microfiber-nanofilm interconnection network at the oil/water interfaces to stabilize the emulsions. Fish oil-loaded RSF-stabilized Pickering emulsions showed low creaming (0% ≤ creaming index < 10%) during the 31-day storage at room temperature, which was lower than the creaming index values (10–47%) of the emulsions in previous report. Moreover, RSF is an excellent emulsifier to prepare semigel and gel of fish oil-loaded RSF-stabilized Pickering emulsions. For the RSF-stabilized Pickering emulsions, a lower oil/water volume ratio might induce lower initial droplet size, slower droplet coalescence, slower liquid-gel transition, and lower creaming stability. In addition, higher homogenization energy input (speed and time) and RSF concentration might induce lower initial droplet size, slower droplet coalescence, faster liquid-gel transition, and higher creaming stability for Pickering emulsions. Therefore, RSF could have good emulsion stabilization ability by adjusting preparation parameters and is a promising emulsifier to prepare emulsion semigel and gel in the field of food emulsions. This work provided useful information to understand the effects of preparation parameters on the formation and stability of RSF-stabilized emulsions.

Effect of ionic strength, pH and temperature on the behaviour of re-dispersed BC:CMC - A comparative study with xanthan gum

The rheological performance of bacterial cellulose and carboxymethyl cellulose (BC:CMC) dry formulations with mass ratios of 1:1, 1:0.75 and 1:0.5 was compared with that of a commercial xanthan gum. The zero-shear viscosity and the yield stress of these hydrocolloids, at concentrations ranging from 0.001% to 0.5% (w/w), were determined by fitting the Cross and Herschel-Bulkley models to the flow curves. Only BC:CMC formulations presented a measurable yield stress, the highest value (1.54 ± 0.17 Pa) being obtained for the 1:0.5 ratio at a concentration of 0.5%. This formulation also presented the highest values of dynamic moduli, namely G′, indicating a stronger solid-like character. Contrarily to xanthan gum, BC:CMC formulations' viscosity profile in aqueous solution was not considerably affected by the pH (in the range from 2.8 to 10.4), the ionic strength (NaCl from 0 mM to 350 mM) or the temperature (6–80 °C). Food grade sunflower oil-in-water emulsions (20% oil) were prepared with 0.3% of the test hydrocolloids, with 150 mM NaCl and pH 3.5. Emulsions with BC:CMC in the ratios of 1:0.75 and 1:0.5 had smaller droplets, stronger solid-like behaviour and resisted centrifugation with little phase separation. These results confirm the high performance of the dry BC:CMC formulations in the stabilization of colloidal systems. • Dry formulations of bacterial cellulose and carboxymethyl cellulose in different mass ratios were prepared. • Higher fibre content in the formulations results in improved rheological properties. • BC:CMC's viscosity is not significantly affected by changes in pH, ionic strength or temperature. • BC:CMC may offer competitive advantages over xanthan gum in the stabilization of food emulsions.

Antibacterial and Antiproliferative Activities of Azadirachta indica Leaf Extract and Its Effect on Oil-in-Water Food Emulsion Stability.

The present study aims to identify and quantify the phenolic compounds of Azadirachta indica leaf extract using HPLC-MS and to evaluate the antioxidant, antibacterial (against different Gram-positive and negative bacteria) and in vitro anti-proliferative activities of this extract (against breast, human liver and cervix adenocarcinoma-derived cells). The application of this extract as a natural antioxidant for food preservation was also tested on oil-in-water food emulsions for the first time in the present work in order to determine the use of Azadirachta indica leaves as a natural additive to preserve the food against lipid oxidation and rancidity. The results obtained revealed that 50%-aqueous ethanol leaf extract showed the best extraction yield (25.14%), which was characterized by a high content in phenolic compounds and strong antioxidant activity. Moreover, this leaf extract inhibited the growth of the bacterial strains tested (Staphylococcus aureus, Escherichia coli, Salmonella paratyphi and Micrococcus luteus) and showed better anti-proliferative activity against breast and cervix adenocarcinoma-derived cells than human liver cancer cells after 48 h of treatment. Additionally, Azadirachta indica leaf extract showed almost similar effects as gallic acid solutions (0.25% and 0.5%) in preserving the oxidation of oil-in-water food emulsions and prevented the formation of secondary oxidation products (malondialdehyde) as well. The results obtained suggested that extracts of Azadirachta indica leaves are a potential source of antioxidant and antibacterial compounds and pointed to the potential of these natural extracts as therapeutic agents.

Characterization, Bioactivity and Application of Chitosan-Based Nanoparticles in a Food Emulsion Model

In this study, chitosan nanoparticles (CNPs) were prepared by the ionic gelation technique with tripolyphosphate (TPP), and the effect of CNP composition and physicochemical characteristics were evaluated. After the synthesis optimization, CNPs were used as carriers for a fish protein hydrolysate (FPH) with bioactive properties (CNPH). The physicochemical characteristics, antioxidant capacity and antimicrobial, antihypertensive and emulsifier properties of unloaded and loaded CNPs in a food system model were studied. CNPH showed a uniform particle distribution, size ~200 nm, high stability (zeta potential around 30 mV), radical scavenging activity and increased antimicrobial activity against Staphylococcus aureus, Shigella sonnei and Aeromonas hydrophila. Additionally, CNPH showed an angiotensin I-converting enzyme (ACE)-inhibitory activity of 63.6% and, when added to a food emulsion model, this system containing CNPs, with or without FHP, exhibited improved food emulsion stability. Thus, CNPs were able to carry the FPH while maintaining their bioactive properties and can be an alternative to the delivery of bioactive peptides with potential as an emulsion stabilizer for food applications.

Study on physicochemical characteristics of lutein nanoemulsions stabilized by chickpea protein isolate-stevioside complex.

Chickpea protein isolate (CPI) originating from chickpeas has the advantages of facilitating the stability of food emulsions. Stevioside (STE) exhibits a notable surface activity and can improve the water solubility of numerous hydrophobic nutrients. STE and protein mixtures show great potential as emulsions stabilizers. The present study aimed to prepare a novel nanoemulsion for encapsulating lutein (LUT) by ultrasonic homogenization using chickpea protein isolate-stevioside complex (CPI-STE) as a stabilizer and also to investigate the physicochemical characteristics. The results obtained showed that different preparation conditions demonstrated significant influences on the physicochemical properties of CPI-STE-LUT nanoemulsions. Under the optimal condition, the average particle size of CPI-STE-LUT nanoemulsions was 195.1nm, and the emulsifying and encapsulation efficiencies of lutein were 91.04% and 87.56%, respectively. CPI-STE-LUT nanoemulsions stabilized by CPI-STE could significantly increase the emulsifying and encapsulation efficiencies of lutein compared to that stabilized by CPI. Fourier transform infrared spectroscopy revealed that hydrogen bond was the main binding force of CPI and lutein, and there was a covalent bond between the two molecules. Furthermore, the stability of CPI-STE-LUT nanoemulsions in gastrointestinal phase was higher than that of CPI-LUT nanoemulsions, which could load lutein more effectively and be more resistant to digestive enzymes. The present study reports the physicochemical characterization of CPI-STE-LUT nanoemulsions for the first time. CPI-STE-LUT nanoemulsions were characterized by a small average particle size lower than 200 nm, as well as high emulsifying and encapsulation efficiencies, and good stability. © 2021 Society of Chemical Industry.

Physical and oxidative stability of food emulsions prepared with pea protein fractions

There is a growing interest in replacing dairy proteins with their plant-based counterparts in food emulsions. Plant proteins generally contain a substantial insoluble protein fraction, of which the properties may differ from the soluble proteins. Therefore, the use of a commercial pea protein isolate, its insoluble fraction and whey protein isolate to stabilize oil-in-water (O/W) emulsions is explored.In 100 g/kg O/W emulsions, the use of full pea protein isolate led to physically instable emulsions that showed droplet flocculation and coalescence, whereas its insoluble fraction and whey protein formed physically stable emulsions. The insoluble pea protein fraction was also able to physically stabilize high internal phase O/W emulsions (HIPEs) containing 700 g/kg oil, giving ~10 times higher viscosity than whey protein-based HIPEs.Under oxidative conditions, whey protein-stabilized emulsions showed extensive coalescence, and fast formation of lipid oxidation products. Insoluble pea protein-stabilized emulsions, showed fast lipid oxidation, but this did not affect the physical stability. In contrast, full pea proteins-based emulsions were physically instable in oxidative conditions but showed the lowest accumulation of oxidation products. These results suggest that the constituents of commercial pea protein isolate have specific functionalities, which is important knowledge for the design of stable plant protein-based emulsions.

Quantitative and Predictive Modelling of Lipid Oxidation in Mayonnaise.

Food emulsions with high amounts of unsaturated fats, such as mayonnaise, are prone to lipid oxidation. In the food industry, typically accelerated shelf life tests are applied to assess the oxidative stability of different formulations. Here, the appearance of aldehydes at the so-called onset time, typically weeks, is considered a measure for oxidative stability of food emulsions, such as mayonnaise. To enable earlier assessment of compromised shelf-life, a predictive model for volatile off-flavor generation is developed. The model is based on the formation kinetics of hydroperoxides, which are early oxidation products and precursors of volatile aldehydes, responsible for off-flavor. Under accelerated shelf-life conditions (50 °C), hydroperoxide (LOOH) concentration over time shows a sigmoidal curvature followed by an acceleration phase that occurs at a LOOH-concentration between 38–50 mmol/kg, here interpreted as a critical LOOH concentration (CCLOOH). We hypothesize that the time at which CCLOOH was reached is related to the onset of aldehyde generation and that the characterization of the LOOH-generation curvature could be based on reaction kinetics in the first days. These hypotheses are tested using semi-empirical models to describe the autocatalytic character of hydroperoxide formation in combination with the CCLOOH. The Foubert function is selected as best describing the LOOH-curvature and is hence used to accurately predict onset of aldehyde generation, in most cases within several days of shelf-life. Furthermore, we find that the defining parameters of this model could be used to recognize antioxidant mechanisms at play.

Novel emulsions–based technological approaches for the protection of omega–3 polyunsaturated fatty acids against oxidation processes – A comprehensive review

Over recent decades, the therapeutic properties and health beneficial effects of omega-3 polyunsaturated fatty acids (omega-3 PUFAs) have been identified. These also contain a number of double bonds which make them highly reactive and, as a consequence, they are susceptible to oxidation. This is one of the main limitations when incorporating them into food matrices. This review article presents the state-of-the-art on the preparation of simple or multiple omega-3 PUFA-based lipid emulsions and other novel systems that have been developed, such as self-assembling systems or solid lipid nanoparticles. Furthermore, the main factors that impact lipid oxidation rate are comprehensively reviewed, highlighting the importance of proteins for increasing the physical stability of food emulsions. Currently, there are several works focused on simple emulsions enriched with omega-3 PUFAs that seek the definition of strategies to allow the control of lipid oxidation. Multiple emulsions and other novel systems are beginning to be considered as a possible alternative to conventional emulsions. This knowledge can be used to facilitate selection of the most appropriate system for the food industry.

Carboxymethyl cellulose/okara protein influencing microstructure, rheological properties and stability of O/W emulsions.

The role of protein-polysaccharide interactions and their mixtures has been a vital factor affecting the formation and stability of food emulsions. Okara protein (OP), which is extracted from the by-product of soybean processing, has received much attention because of its abundant sources and potential attributes with respect to food formulation. Carboxymethyl cellulose (CMC), a well-known food-grade polysaccharide additive, has been widely utilized in the protein-polysaccharide system, whereas, among the proteins, the role of OP has not yet been explored. The present study first assessed the ζ-potential and hydrodynamic diameter of aqueous mixtures containing OP (1.0wt%) and CMC (0-0.5wt%), followed by the investigation of OP-CMC mixtures stabilized O/W emulsions. As CMC increased, oil droplet size, surface protein adsorption, apparent viscosity and storage modulus increased, whereas the loss tangent decreased. CMC resulted in emulsion destabilization compared to emulsions without CMC, whereas a higher concentration of CMC promoted emulsion stability against creaming for emulsions in the presence of CMC. The results provide information with respect to OP and CMC being incorporated into food formulations and also strengthen our understanding of the related mechanism, in addition to facilitating the further utilization of OP. © 2020 Society of Chemical Industry.

Impact of Phytic Acid on the Physical and Oxidative Stability of Protein-Stabilized Oil-in-Water Emulsions

The effects of phytic acid on the physical and oxidative stability of flaxseed oil-in-water emulsions containing whey protein-coated lipid droplets were investigated. The surface potential, particle size, microstructure, appearance, and oxidation of these emulsions were monitored when they were stored at pH 3.5 and 7.0 for 25 days in the dark (37 °C). The phytic acid and protein-coated lipid droplets had similar charges (both negative) at pH 7.0, but had opposite charges (negative and positive) at pH 3.5. At pH 7.0, the addition of phytic acid had no impact on the physical stability of the emulsions but significantly improved their oxidative stability, which was attributed to its ability to sequester pro-oxidant transition metals (iron ions). At pH 3.5, extensive droplet aggregation and creaming occurred in the emulsions containing phytic acid, which was ascribed to charge neutralization and ion bridging. The oxidative stability of the acidified emulsions, however, still increased after addition of phytic acid, which was again attributed to its ability to chelate iron ions. Interestingly, the antioxidant activity of phytic acid decreased as its level was increased. Our results suggest that phytic acid may be used as a natural antioxidant to improve the oxidative stability of food emulsions containing polyunsaturated fatty acids, but its level must be carefully controlled.

Droplet and creaming stability of fish oil-loaded gelatin/surfactant-stabilized emulsions depends on both the adsorption ways of emulsifiers and the adjusted pH

The droplet and creaming stability of food emulsions stabilized by mixed emulsifiers is a research hotspot in the field of emulsions. In this work, we mainly explore the effect of pH change on the droplet and creaming stability of fish oil-loaded emulsions synergetically (Span 80 and SL) or competitively (Tween 80 and SDS) stabilized by gelatin/surfactant. The results demonstrate that initial droplet stability and droplet storage stability, and creaming stability of the pH-adjusted emulsions are dependent on both the adsorption ways of emulsifiers and the adjusted pH: (1) Competitively stabilized emulsions have more stable droplets than synergetically stabilized emulsions; (2) SDS-dominant competitively stabilized emulsions have more stable droplets than gelatin-dominant emulsions; (3) Basic pH-adjusted emulsions have more stable droplets than acidic pH-adjusted emulsions; (4) The synergetically stabilized emulsions at acidic pH have significantly higher creaming indexes than that at basic pH; and (5) The competitively stabilized emulsions have high or similar creaming indexes to that at acidic pH. Further, the mechanisms are proposed according to Stokes’ Law. This work will provide useful information to understand the interfacial properties of mixed emulsifiers in the food emulsions and promising application perspective for the development of food beverages including acidic and alkali beverages.

Food-Grade Emulsions and Emulsion Gels Prepared by Soy Protein-Pectin Complex Nanoparticles and Glycyrrhizic Acid Nanofibrils.

Glycyrrhizic acid (GA) and GA nanofibrils (GN) have been shown to be efficient natural emulsifiers for formation and stabilization of food emulsions. In this work, the emulsion properties of GN in the presence of soy protein isolate-pectin complex nanoparticles (SPNPs) were studied to understand the impact of the nanofibril-nanoparticle interactions on emulsion stabilization. In the presence of low GN concentrations (0.1-0.5 wt %), the synergy in reducing the interfacial tension was observed due to SPNPs-GN complexation in the bulk and at the interface by hydrogen bonding, endowing the prepared emulsions with an overall smaller droplet size. However, obvious flocculation and clustering of oil droplets occurred in these emulsions (especially at 0.25 and 0.5 wt % GN), which are probably induced by a depletion mechanism. At high GN concentrations (1-2 wt %), due to the preferential adsorption, the GN mainly dominated the interface and the subsequent formation and properties of emulsions. Accordingly, the self-standing emulsion gels were obtained, showing a small droplet size with d32 of about 1.0-1.5 μm, homogeneous appearance and microstructure, and encouraging rheological properties including high gel strength, shear sensitivity, and good thixotropic recovery. This is mainly attributed to the formation of a fibrillar hydrogel network in the continuous phase as well as around the droplet surfaces.

Antioxidant activity of polyphenolic extracts of filamentous fungus Mucor circinelloides (WJ11): Extraction, characterization and storage stability of food emulsions

Optimized extraction of antioxidants from Mucor circinelloides WJ11 (MCWJ11) biomass was studied. Storage, stability, composition and antioxidant properties in model food emulsion systems were also investigated. Both the extraction approach and solvent type were found to significantly (p<0.05) influence the recovery yield of antioxidants and their antioxidant capacity. The 90% aqueous binary solvent system with semi-polar solvents (i.e., acetone and ethanol) showed increased recovery levels of TPC, TFC and TCT, with the highest antioxidant bioactivity obtained using a pressurized liquid extraction. Ninety-day storage studies of microbial ethanolic extracts with accelerated storage/processing showed increased degradation of antioxidants at elevated temperatures (22–28 oC), with a negligible influence of white light. Substantial loss of microbial polyphenolic compounds was also observed, especially in fetal bovine serum at 37 °C with a 48 h stability test in biologically relevant buffers. Liquid–liquid fractionation of microbial ethanolic extracts led to the most active antioxidative fractions with ethyl acetate and 1-butanol. Comparatively, EtAc had better antioxidative activity (in a dose-dependent manner) against lipid oxidation in the tested food model emulsion systems. Furthermore, metabolic fingerprinting of the ethanolic extracts showed that the secondary metabolites of MCWJ11 were alkaloids, pigments, benzoic acids, terpenoids, cinnamic acids, benzopyrans, aspalathins and phloretins.

Effects of Water Soluble Materials on Water-in-oil Primary Food Emulsion Stability

Effects of Water Soluble Materials on Water-in-oil Primary Food Emulsion Stability

Impact of interfacial composition on co-oxidation of lipids and proteins in oil-in-water emulsions: Competitive displacement of casein by surfactants

In this study, the interfacial composition of protein-stabilized emulsions was manipulated by adding a small molecule surfactant to induce displacement of the adsorbed protein. The rate and extent of lipid and protein oxidation was then measured for emulsions with different interfacial compositions. Lipid and protein co-oxidation were studied in walnut oil-in-water (O/W) emulsions (5% v/v oil, 1.0% w/v protein, 0–1.0% w/v Tween 20, pH 7). The interfacial tension, protein surface load, surface potential, and mean particle size of the emulsions decreased as the surfactant concentration increased, suggesting that caseinate was displaced by Tween 20. Emulsions stabilized solely by caseinate exhibited relatively slow lipid oxidation when incubated in the dark at 45 °C for up to 8 days, as determined by lipid hydroperoxides and 2-thiobarbituric acid-reactive substances (TBARS). In contrast, the caseinate itself was rapidly oxidized, as shown by carbonyl formation, intrinsic fluorescence loss, and electrophoresis measurements. Competitive displacement of adsorbed caseinate by Tween 20 reduced protein oxidation but promoted lipid oxidation, indicating that adsorbed proteins were more sensitive to oxidation themselves but also more efficient at protecting lipids from oxidation than non-adsorbed ones. These results demonstrate the important role that interfacial composition plays on the oxidative stability of food emulsions containing mixtures of emulsifiers.

Применение ультразвуковой кавитации в пищевой промышленности

This article describes the benefits of using the effect of ultrasonic treatment on the nutritional environment in comparison with other types of commonly used processing methods – cutting, heat treatment, mixing. Particular attention is paid to the use sonochemical effects when emulsified liquid food media. The concrete examples and shows promising use of this type of actions to ensure the stability of food emulsions.

Rheological properties of oil-in-water emulsions prepared with oil and protein isolates from sesame (Sesamum Indicum)

In this study, food emulsions of oil in water from sesame (Sesamum indicum) protein isolates and their oil were formulated and standardised. The effect of the concentrations of sesame (Sesamum indicum) protein isolates and base oil and the speed of the emulsification process for the food emulsion stability was studied. The protein isolates were achieved from the defatted sesame flour (DSF), obtaining a percentage of 80% ± 0.05% of protein. Emulsions were formulated through a factorial design 23. The rheological behaviour of sesame (Sesamum indicum) protein isolates-stabilised emulsions and microstructural composition were investigated. Stable emulsions with suitable rheological properties and microstructure were formulated at a concentration of 10% sesame oil and different concentrations of protein isolates, between 1.5% and 2.5%, with the best droplet distribution characteristics being shown for the 2.5% sesame protein isolates. The emulsions showed a non-Newtonian fluid behaviour, adjusting the Sisko model.

Kinetic effects on interfacial partitioning of fat crystals

Abstract Fat crystals, like other colloidal particles, can influence the stability of food emulsions. Unlike colloidal particles added to form Pickering emulsions, however, crystals form within food emulsion droplets via crystallization and then the crystal wettability determines its ultimate partitioning relative to the oil–water interface. Most descriptions of crystal partitioning assume the final interfacial state of fat crystals can be predicted by key system properties like interfacial tension and contact angle. However, recent work has shown the kinetics of interfacial particle adsorption can be surprisingly slow as a result of variables like particle roughness as well as internal droplet rheology. This work examined the effects of common variables, normally not thought to control crystal partitioning, on the state of crystals in a milkfat emulsion. For example, crystallization dynamics, tuned by varying surfactant adsorption and the crystallization driving force, are found to alter interfacial partitioning of milkfat crystals at oil–water interfaces. Slower crystallization rates increase the likelihood that crystals will leave the droplets by dewetting and reside in the aqueous phase, even with no compositional changes. The tendency of fat crystals to dewet the liquid oil increased as the oil–water interfacial tension, and the contact angle of aqueous surfactant on fat crystals, decreased. Several possible explanations for the results observed are postulated.

Interfacial peptide partitioning and undiminished antioxidative and emulsifying activity of oxidatively stressed soy protein hydrolysate in an O/W emulsion

Peptides as surfactants are able to neutralize radicals, but their ability to maintain physical and chemical stability of food emulsions when oxidatively stressed is not clear. In this study, the distribution of peptides present in hydroxyl radical-stressed soy protein hydrolysate (SPH) at the interface and the inhibition of lipid oxidation in an oil-in-water (O/W) emulsion were investigated. O/W emulsions (10 g/100 g soybean oil, 20 mg/mL protein, 1 g Tween 20/100 g emulsion) were prepared under 138 MPa and stored for 14 days. Morphology of emulsion droplets was observed using phase contrast, confocal laser scanning, and transmission electron microscopy. The stability of all emulsions gradually decreased during storage due to flocculation but not coalescence. Oxidized nonhydrolyzed soy protein (SP) and SPH, despite 3–4-fold increases in carbonyls, retained up to 74% of their power to inhibit lipid oxidation in emulsions when compared with nonoxidized counterparts. Nonpolar peptides in SPH had a preferred adsorption at the interface while oxidation decreased the selectivity. In conclusion, oxidation that produces 4-fold carbonyl increases modifies the distribution of peptides without significantly affecting their function as emulsifiers and does not eliminate their antioxidant capacity.

Enhancing the oxidative stability of food emulsions with rice dreg protein hydrolysate

Rice dreg protein hydrolysates (RDPH) can potentially be used as natural antioxidants for a variety of emulsion-type food systems. They contained 89.9% protein, 934.2mg/g total amino acids with 517.7mg/g total hydrophilic amino acids, and 78% peptides smaller than 5kDa. Here, the physical and oxidative stabilities of corn oil-in-water emulsions (10wt.% lipid) containing RDPH (0–20mg/mL) and stabilized by Tween-20 were investigated as a function of RDPH concentration and pH. The results showed that emulsions with RDPH and Tween-20 emulsions did not experience coalescence (when RDPH concentration<20mg/mL), and were more stable than emulsions prepared by either emulsifier alone (RDPH or Tween-20). RDPH and Tween-20 could not prevent coalescence, because when RDPH=20mg/mL, competitive adsorption existed at the interface between high concentrations RDPH and Tween-20. The negatively charged emulsion stabilized with 5mg/mL RDPH and Tween-20 was found to be more stable at pH 5. RDPH was able to inhibit lipid oxidation, reducing the formation of lipid hydroperoxides and TBARS with increasing RDPH concentrations. Similarly the increase in pH also reduced oxidation, possibly by scavenging free radicals and chelating pro-oxidant metals. The antioxidant properties of RDPH at the interface of emulsion droplets would render them suitable as natural antioxidants in some food products.