Stability of oil–water primary emulsions stabilised with varying levels of casein and whey proteins affected by high-intensity ultrasound

This study evaluates physical and chemical stability of ultrasound-assisted grape seed oil primary emulsions stabilised by varying compositions of caseins to whey proteins (80:20, 60:40, 50:50 and 40:60) at different sono-operating conditions (81.9 and 117.0 J mL⁻¹). Physical and chemical stabilities were influenced by both sonication energy densities and milk protein compositions. Emulsions prepared at 81.9 J mL⁻¹ energy density with ≥40% whey protein fraction (60:40, 50:50, 40:60 and WPI) showed greater physical stability than the emulsions sonicated at 117.0 J mL⁻¹ which exhibited physical instability due to the depletion flocculation mechanism at the critical casein concentration (≥40%). The emulsion oxidative stability was found to be affected by sonication conditions as 117.0 J mL⁻¹ induced the oxidation reactions once the whey concentration exceeds 40%. Therefore, ultrasound prepared emulsions with casein to whey ratios of 60:40, 50:50, 40:60 and WPI at 81.9 J mL⁻¹ energy density was found to be stable for 10 days at 4 °C.     

Interfacial characteristics and microchannel emulsification of oleuropein-containing triglyceride oil–water systems

This study investigated the adsorption characteristics of olive leaf water extract and its major phenolic compound, oleuropein, at the triglyceride oil–water interface. We also investigated the preparation characteristics of food-grade triglyceride oil-in-water (O/W) emulsions stabilized by oleuropein using microchannel (MC) emulsification. Refined soybean oil, extra virgin olive oil, refined olive oil, and medium-chain triacylglyceride (MCT) oil were used as triglyceride oils. Both olive leaf extract (OLE) and highly purified oleuropein had a pronounced ability to decrease the interfacial tension at the refined soybean oil–water interface. The packing of oleuropein molecules at the triglyceride oil–water interface was estimated on the basis of their surface excess concentration and area occupied per molecule, determined from the Gibbs adsorption equation. MC emulsification was performed using a silicon grooved MC array plate (model CMS6-2). The continuous aqueous phase contained 0.6 wt.% of oleuropein. Monodisperse, oleuropein-stabilized O/W emulsions with an average droplet diameter of 25 μm and coefficient of variation (CV) of < 5% were produced in all systems, except the MCT oil-containing system, even in the absence of a cross-flowing continuous phase. This successful MC emulsification was observed without droplet coalescence for 15 h of continuous operation. Our findings demonstrate that the use of oleuropein, which has an interfacial activity, is capable of producing monodisperse O/W emulsions using MC emulsification and stabilizing the generated oil droplets when appropriate types of triglyceride oils are used.     

A comprehensive review on polarity,partitioning, and interactions of phenolic antioxidants at oil–water interface of food emulsions

There has been a growing interest in developing effective strategies to inhibit lipid oxidation in emulsified food products by utilization of natural phenolic antioxidants owing to their growing popularity over the past decades. However, due to the complexity of emulsified systems, the inhibition mechanism of phenolic antioxidants against lipid oxidation is rather complicated and not yet fully understood. In order to highlight the importance of polarity of phenolic antioxidants in emulsified systems according to the polar paradox, this review covers the recent progress on chemical, enzymatic, and chemoenzymatic lipophilization techniques used to modify the polarity of antioxidants. The partitioning behavior of phenolic antioxidants at the oil–water interface, which can be influenced by the presence of synthetic surfactants and/or antioxidant emulsifiers (e.g., polysaccharides, proteins, and phospholipids), is discussed. In addition, the emerging phenolic antioxidants among phenolic acids, flavonoids, tocopherols, and stilbenes applied in food emulsions are elaborated. As well, the interactions of polar–nonpolar antioxidants are stressed as a promising strategy to induce synergistic interactions at oil–water interface for improved oxidative stability of emulsions.     

Hydroxypropylmethylcellulose–β-lactoglobulin mixtures at the oil–water interface. Bulk,interfacial and emulsification behavior as affected by pH

In this work we have studied the bulk, interfacial and emulsification behavior of a surface-active polysaccharide, hydroxypropylmethylcelulose (HPMC) and β-lactoglobulin (βlg) mixtures at two pHs, 3 and 6.     

Brewster angle microscopy of adsorbed protein films at air–water and oil–water interfaces after compression,expansion and heat processing

Recent Brewster angle microscopy (BAM) observations of adsorbed films of proteins at the air-water (A–W) and oil–water (O–W) interfaces are reviewed and compared. At the A–W interface β-lactoglobulin (β-L) and ovalbumin (OA) were studied at pH 7 and 5. At the O–W interface β-L, α_s1-, β- and κ-caseins were studied at pH 7. The adsorbed films were periodically subjected to compression and expansion cycles such that the film area was typically varied between 125% and 50% of the original film area. At the A–W interface, little structure was observable on compression or expansion or aging, especially at pH 7. For ovalbumin at pH 5, some cracks and ridges in the films appeared. But, for both β-L and OA, such features became much more obvious on addition to the interface of a low area fraction (<0.01%) of 20 μm polystyrene latex (PS) particles. With particles present the structuring was also more obvious at pH 5 (closer to the protein isoelectric point) than at pH 7, and for greater adsorption times and/or higher bulk protein concentration (C_b). Particle addition was not necessary to highlight folding and ridges that occurred at the O–W interface for β-L. After heating to 80 and 90 °C, β-L films adsorbed from low C_b (0.005 wt%) even greater film structuring was evident. However, β-L films adsorbed from higher C_b (≥0.05 wt%) showed fewer, but more pronounced ridges and cracks. The caseins at the O–W interface showed comparatively little evidence of structuring, either before or after heating. A measure of the dilatational elastic modulus of the films correlated with the observed variations in the structural integrity of the films. Clearly, protein films subjected to these types of thermal and mechanical perturbations can become highly inhomogeneous, depending on the type of protein and the bulk solution conditions, with implications for the stability of the corresponding foams and emulsions. This is in agreement with earlier computer simulations. Protein films at the O–W interface (particularly after heating) appear to be more resilient and less aggregated than films at the A–W interface.     

Effects of ultrasonic treatment on the gel properties of microbial transglutaminase crosslinked soy,whey and soy–whey proteins

Food Science and Biotechnology - This paper studied the influences of diverse ultrasonic power treatments on the physico-chemical properties of soy–whey mixed protein induced by microbial...     

Facial preparation of superhydrophobic and superoleophilic textiles by depositing nano-SiO2 for oil–water separation

In this study, a facile one-step dip-coating approach was reported for the fabrication of superhydrophobic and superoleophilic cotton fabrics for oil–water separation. By depositing the hydrophobic nano-SiO₂ on the micro-scale cotton fabric surface, the combination of the nano-SiO₂ and the micro-roughness cotton fabric created a micro/nano-binary surface roughness and presents superhydrophobicity and superoleophilicity. SEM, EDS, and TGA result shows that the treated cotton fabric was completely covered by the nano-SiO₂ particles when the nano-SiO₂ particles was about only 3.6 wt% of the pristine cotton fabric. The separation efficiency of the fabricated superhydrophobic and superoleophilic fabric was calculated up to 98.3 wt%. The one-step production technique described here is realizable for industrial use, relatively mild processing conditions, and large-scale fabrication.     

Influence of environmental stresses on the physicochemical stability of orange oil bilayer emulsions coated by lactoferrin–soybean soluble polysaccharides and lactoferrin–beet pectin

Based on layer-by-layer electrostatic deposition, orange oil bilayer emulsions stabilized with lactoferrin (LF)–soybean soluble polysaccharides (SSPS) and lactoferrin (LF)–beet pectin (BP) were prepared. The effect of environmental stresses (ionic strength, pH, freeze–thaw and light) on the physicochemical stability of primary and secondary emulsions was investigated. In the absence of anionic polysaccharides, orange oil emulsion was highly unstable and aggregated at pH 7–9 and NaCl of 0.1–0.5 M. The droplets in LF–SSPS coated emulsion were stable against aggregation at pH range of 3–10 and NaCl concentration less than 0.3 M, while the droplets in LF–BP coated emulsion were stable against aggregation at pH 4–9 and NaCl concentrations of 0–0.5 M. All the primary and secondary emulsions showed the instability after the freeze–thaw treatment and the stability could be improved in the presence of maltodextrin. During the light exposure (0.35 W/m², 45 °C) for 8 h, the bilayer emulsions could protect key volatile compounds (decanal, octanal and geranial) from the oxidation compared with the primary emulsions. These results suggested that the layer-by-layer electrostatic deposition could improve the stability of LF-coated emulsion to environmental stresses.     

Characteristics of anthocyanins in fortified cakes: a promising potent inhibitor of sucrase, α-glucosidase and lipase

Anthocyanins are well-known compounds that can improve gastrointestinal effects and have the potential to be utilised as an ingredient in functional foods. However, the true pharmacological role that they carry out in human body has been largely elusive. Thus, this study was aimed to investigate the inhibitory action of anthocyanins in a cake matrix on intestinal enzymes – α-glucosidase, sucrase and lipase. Anthocyanin-rich black rice extract powder (ABREP) was incorporated into cake at the levels of 0, 0.25, 0.5, 1 and 2% of flour weight. The physicochemical properties and in vitro digestibility of the cake, as well as enzyme inhibitory effects of anthocyanins were investigated. Degradation of anthocyanins in the batter occurred up to 68% at the 2% fortification level while the cake matrix asserted a protective effect on the remaining anthocyanins, keeping them by up to 84% after baking. The antioxidant capacity of cakes was increased by nine times when cake was fortified with 2% ABREP. The digestion rate of sucrose was reduced by 4.6 times at a 2% fortification level as compared to the control. Furthermore, cake with 2% ABREP addition showed 150%, 41% and 278% higher inhibitory effects against sucrase, α-glucosidase and lipase as compared to the one with 0.5% addition, respectively. This study provides an in-depth understanding of the potential of anthocyanin-fortified foods for helping people with elevated blood glucose and triglyceride levels.     

Thermal treatment to form a complex surface layer of sodium caseinate and gum arabic on oil–water interfaces

This study reported an alternative approach to electrostatic interaction to generate a biopolymer complex surface layer on emulsion droplets. By increasing the temperature, a complex surface layer of sodium caseinate (CN) and gum arabic (GA) on emulsion droplets could be formed either through the adsorption of complexes formed in the solution or through direct complexation of CN and GA with the surface. Mixtures of CN and GA were heated at pH 7 and then used to form oil-in-water emulsions at high temperatures. Changes in the average particle size and the ζ-potential of the emulsions indicated that complexes of GA and CN adsorbed to the interface at temperatures above 60 °C. A thick complex surface layer was also observed using confocal laser scanning microscopy. The addition of GA or CN to emulsions made with CN or GA resulted in an apparent binding of GA or CN to the emulsion droplets that depended on the sequence of addition. This temperature-induced formation of a complex surface layer was considered to be due to hydrophobically driven complexation between CN and the protein fraction of GA. The formation of the complex surface layer was dependent on the concentration, the temperature, and the addition order of the second component. This finding may imply an alternative option for the formation of biopolymer multilayers or complex surface layers on colloidal particles.     

Effect of iron chelates on oil–water interface,stabilized by milk proteins: The role of phosphate groups and pH. Prediction of iron transfer from aqueous phase toward fat globule surface by changes of interfacial properties

Iron incorporated into food systems induces oxidation and precipitation. The consequences are reduced bioavailability and a functional modification of other food components such as proteins. The iron-chelates such as ferrous bisglycinate represent a possibility to avoid side effects, since the iron is protected. The aim of this study is to investigate the effects of iron-chelates compounds on the properties of an oil/water interface stabilized by caseinate or β-lacotoglobulin, under environmental conditions at 20 °C. Analyses were performed using dynamic drop tensiometry during 5000 s. The aqueous bulk phase is an imidazole/acetate buffer (0.1 M), containing 0.4 × 10⁻⁶ M protein, and 0.2 × 10^-6 9 M iron-chelates compounds. The results indicate that, under neutral conditions, the addition of some irons salts (NaFe-EDTA or Fe-bisglycinate) do not change the structure of the interface stabilized by a protein containing no phosphate groups (β-lactoglobulin). In the case of caseinate, NaFe-EDTA addition increases the lowering rate of surface tension at pH 6.5. On the contrary, the lowering rate of surface tension with caseinate is inhibited by Fe-bisglycinate at pH 6.5. Such an effect is not observed with β-lactoglobulin. The low transfer of irons ions from the bulk to the interface stabilized by β-lactoglobulin is confirmed by zetameter and FTIR measurements. These results indicate an effective strategy to follow for controlling the physical and chemical stability of an emulsion stabilized with proteins.     

Strecker aldehydes and α-keto acids,produced by carbonyl–amine reactions,contribute to the formation of acrylamide

The formation and disappearance of acrylamide in binary and ternary mixtures of asparagine (or acrylamide), carbonyl compounds and amino acid derivatives was studied in an attempt to understand the different reactions produced in mixtures of carbonyl compounds and amino acids. The carbonyl compounds assayed included glucose, 2,4-decadienal, mercaptopyruvic acid, phenylpyruvic acid, and phenylacetaldehyde. The assayed amino acids were cysteine, N-acetylcysteine, and phenylalanine, in addition to asparagine. All assayed carbonyl compounds were able to convert asparagine into acrylamide to various extents, and some of them were more reactive than glucose. In addition, they inhibited the Michael additions responsible for acrylamide disappearance. On the other hand, the addition of amino acids mostly resulted in decreases of acrylamide, although acrylamide also increased in some mixtures. Amino acids decreased acrylamide yield because of both their competence with asparagine for carbonyl compounds and their reaction with the produced acrylamide. However, carbonyl–amine reactions formed new carbonyl compounds, which increased acrylamide content. Therefore, asparagine degradation in the presence of amino acids is likely to be a balance between the decrease of degradation produced by the original carbonyl compounds and the increase of degradation due to the carbonyl compounds formed.     

Development of a genetic method for the identification of salmon,trout, and bream in seafood products by means of PCR–RFLP and FINS methodologies

In the present study, two alternative methods for identifying 13 salmon, trout and bream species were developed. Both of them are based on polymerase chain reaction (PCR) amplification of a cytochrome b gene fragment. Subsequently, different techniques were assayed to assign the PCR amplicons previously obtained to particular species. The first one is based on the restriction fragment length polymorphism (RFLP) and includes three endonucleases for generating species-specific restriction profiles, while the second one is based on the phylogenetic analysis of DNA sequences. The main novelty of this work lies in the applicability of the developed methods to all kinds of processed products, including those undergoing intensive processes of transformation, as for instance canned foods. Finally, the methods were applied to 25 commercial samples including some that had been subjected to intensive thermal treatment, allowing the detection of those incorrectly labeled (16%). Therefore, these methods are useful to check the fulfillment of labeling regulations for seafood products, verify the correct traceability in commercial trade, and for fisheries control.