Synthesis, Characterization and Applications of Spinel Cobaltite Nanomaterials.

Recently, spinel structures (AB2O4) Nanoparticles (NPs) having binary and ternary mixtures of metal oxides have been established as promising redox catalysts. Due to the presence of two mixed valence metal cations, transport of electrons takes place easily between multiple transition-metal cations with relatively low energy of activation. Among these, spinel cobaltite (MCo2O4) is very attractive due to its low cost, non-toxicity, higher stability, higher electronic conductivity and electrochemical property. To date, MCo2O4 has been used in the fabrication of supercapacitors, electrodes for oxygen evolution reaction, and electrochemical sensors for glucose. A variety of MMCo2O4materials have been synthesized, characterized, and utilized in the fabrication of super capacitors, electrodes for oxygen evolution reaction, and electrochemical sensors for glucose. The progress in the field of the spinel MCo2O4 materials opens the door to novel and efficient applications in the nanoscience and nanotechnology, and elctrochemistry.

Corrigendum to "Improved bioaccessibility of polymethoxyflavones loaded into high internal phase emulsions stabilized by biopolymeric complexes: A dynamic digestion study via TNO's gastrointestinal model"[Curr Res Food Sci, Volume 2 (June 2020) 11-19].

[This corrects the article DOI: 10.1016/j.crfs.2019.11.007.].

Improved bioaccessibility of polymethoxyflavones loaded into high internal phase emulsions stabilized by biopolymeric complexes: A dynamic digestion study via TNO's gastrointestinal model.

In this work, the bioaccessibility of polymethoxyflavones (PMFs) loaded in high internal phase emulsions (HIPE, ϕoil = 0.82) stabilized by whey protein isolate (WPI)-low methoxy pectin (LMP) complexes was evaluated using in vitro lipolysis and dynamic in vitro intestinal digestion studies. PMFs loaded HIPE was prepared by using aqueous dispersion of pre-formed biopolymeric complexes (WPI-LMP, 2:1 ratio) as the external phase and medium chain triglycerides oil (containing PMFs extracted from citrus peel) as the dispersed phase. The in vitro lipolysis study revealed that PMFs in HIPE became bioaccessible much higher than PMFs in medium chain triacylglycerols oil (MCT oil). In addition, by simulating the entire human gastrointestinal (GI) tract, the GI model TIM-1 demonstrated a 5- and 2-fold increase in the total bioaccessibility for two major PMFs encapsulated in HIPE, i.e. tangeretin (TAN) and nobiletin (NOB), respectively, as opposed to PMFs in MCT oil. Together these results from the digestion study showed that the incorporation of a high amount of PMFs into the viscoelastic matrix of HIPE could represent an innovative and effective way to design an oral delivery system. Such a system could be used to control and to improve the delivery of lipophilic bioactive compounds within the different compartments of the digestive tract, especially the human upper GI tract.

Advances in our understanding of the structure and functionality of edible fats and fat mimetics.

The reasons for the increased world-wide incidence of obesity, type-2 diabetes, and cardiovascular disease include sedentary lifestyles and poor food choices. Regulatory agencies in several countries now require companies to add unattractive front of package labels to their products where salt, sugar and fat (or saturated fat) levels are prominently displayed. After the demise of partially hydrogenated fats, saturated fat has become the new target. Consumption of saturated fat over polyunsaturated oil has been clearly shown to increase cholesterol levels in humans. However, saturated fats provide the functionality required in many food products. To complicate matters, concerns over sustainability, veganism, genetically modified organisms, animal welfare, as well as religious beliefs, severely limit our sources of saturated fat. In this review we will discuss recent advances in our understanding of the nano and mesoscale structure of fats, responsible for their physical functionality and contrast it to that of fat mimetics. Fat mimetics include polymeric networks of ethylcellulose, emulsion-templated networks of proteins and polysaccharides, colloidal and self-assembled fibrillar networks of polar lipid crystals, as well as solid o/w emulsions of oil trapped within crystallized lamellar mesophases. Clean label and economic considerations will also be touched upon.

Whey protein isolate-low methoxyl pectin nanocomplexes improve physicochemical and stability properties of quercetin in a model fat-free beverage.

In this study, whey protein isolate (WPI)-low methoxyl pectin (LMP) electrostatic complexes were used to encapsulate quercetin (Q) in a model fat-free beverage system. The effect of the pH and WPI : LMP ratio was first studied to form soluble complexes with optimal physical properties, in terms of the hydrodynamic diameter, surface charge, and yield. Based on the results, pH 5.0 and a 2 : 1 (w/w) ratio of WPI : LMP were selected for encapsulation of Q. The stoichiometry of the binding (n) and the binding constant (Kb) of WPI:Q were evaluated at pH values of 5.0 and 7.0 at room temperature. The Q-loaded WPI:LMP nanocomplexes were produced by mixing WPI with Q at two loading concentrations corresponding to 5 : 1 and 1 : 1 WPI : Q molar mixing ratios, followed by the addition of LMP and pH adjustment to 5.0. The microstructure of Q-loaded WPI:LMP complexes was investigated by cryo-SEM imaging. Q was efficiently entrapped at two loading concentrations with an efficiency of about 97%. Q-loaded WPI:LMP complexes showed physical stability during storage and high temperature processing, as well as in the presence of challenging formulation conditions such as a high sugar concentration or salt addition (at a limited concentration). The stability of encapsulated Q against UV irradiation was approximately 4 times better than that of free Q. Moreover, Q-loaded WPI:LMP complexes were also lyophilized into dry powder, which can be useful for practical application in food products.

High internal phase emulsion (HIPE)-templated biopolymeric oleofilms containing an ultra-high concentration of edible liquid oil.

We report, for the first time, the fabrication of oleofilms (containing more than 97 wt% edible liquid oil) using high internal phase emulsions (with oil volume fraction φoil = 0.82) as templates. Advanced microscopy studies revealed an interesting microstructure of these films where jammed oil droplets were embedded in a dried matrix of biopolymeric complexes.

Colloidal particles for the delivery of steroid glycosides.

Water insoluble bioactive molecules with very high melting temperature and low solubility in water are difficult to formulate in food products. We demonstrate the synthesis of nanoscale particles from steroid glycosides using a facile liquid antisolvent precipitation method in the presence of various food grade stabilizers. Colloidal particles with sizes well below 200 nm are prepared from steroid glycosides containing extracts, as well as mixtures with phytosterol. In the mixtures, the formation of the typical for the phytosterol rod-like particles is suppressed. Particle size and structure are investigated by electron microscopy and dynamic light scattering. Due to the presence of surface charge and steric stabilization, colloidal particles do not display aggregation and are stable for a period of longer than one year. The results of this study are important for the formulation and delivery of steroid glycoside and phytosterol bioactive molecules in the fields of food, nutraceuticals, and medical applications.

Phytosterols-induced viscoelasticity of oleogels prepared by using monoglycerides.

Monoglycerides (MGs) and phytosterols (PS) are known to form firm oleogels with liquid oil. However, the oleogels are prone to undergo polymorphic transition over time that lead to crystals' aggregation thus, compromises physical properties. Thus, we combined MGs with PS to control the crystallization and modify the morphology of the combination oleogels, as both components are reported to interact together. The oleogels were prepared at different ratio combinations and characterized in their rheological, thermal, morphology, and diffraction properties. The results showed that the 8:2 MGP:PS exhibited higher storage modulus (G') than the MGP mono-component. The combination oleogels exhibited effects on the crystallization and polymorphic transition. Consequently, the effects led to change in the morphology of the combination oleogels which was visualized using optical and electron microscope. The resultant effect on the morphology is associated with crystal defect. Due to observable crystals of MGP and PS, it is speculated that the combination oleogels formed a mixed crystal system. This was confirmed with diffraction analysis in which the corresponding peaks from MGP and PS were observed in the combination oleogels. However, the 8:2 oleogel exhibited additional peak at 35.41Å. Ultimately, the 8:2 was the optimum combination observed in our study. Interestingly, this combination is inspired by nature as sterols (phytosterols) are natural component of lipid membrane whilst MGP has properties similar to phospholipids. Hence, the results of our study not only beneficial for oil structuring, but also for the fields of biophysical and pharmaceutical.

Mixed surfactant systems of sucrose esters and lecithin as a synergistic approach for oil structuring.

In order to modify the self-assembly of sucrose esters (SEs) in sunflower oil, we added sunflower lecithin (SFL) as co-surfactant. It is hypothesized that SFL modifies the self-assembly of SEs by interrupting the extensive hydrogen bonding between SEs monomers. The addition of SFL into SEs induced gelation of the mixed surfactant system oleogels at all studied ratios. The 7:3 SEs:SFL combination showed enhanced rheological properties compared to the other studied ratios, which suggests better molecular ordering induced by SFL. The modifications might have been caused by interference in the hydrogen bonding, connecting the polar heads of SEs molecules in the presence of SFL. This effect was confirmed by thermal behavior and small angle X-ray diffraction (SAXD) analysis. From the crystallization and melting analyses, it was shown that the peak temperature, shape and enthalpy decreased as the SFL ratio increases. Meanwhile, the bi-component oleogels exhibited new peaks in the SAXD profile, which imply a self-assembly modification. The microscopic study through polarized and electrons revealed a change in the structure. Therefore, it can be concluded that a synergistic effect between SEs and SFL, more particularly at 7:3 ratio, towards sunflower oil structuring could be obtained. These findings shed light for greater applications of SEs as structuring and carrier agent in foods and pharmaceutical.

Chemical profiling of the major components in natural waxes to elucidate their role in liquid oil structuring.

Elucidating the composition of waxes is of utmost importance to explain their behavior in liquid oil structuring. The chemical components (hydrocarbons - HCs, free fatty acids - FFAs, free fatty alcohols - FALs and wax esters - WEs) of natural waxes were analyzed using HPLC-ELSD and GC-MS followed by evaluation of their oil structuring properties. The gel strength, including the average storage modulus and oscillation yield stress, displayed a negative correlation with FALs and a positive correlation with HCs, FFAs and WEs. The components dictating the gel strength are HCs, FFAs and WEs in a descending order of importance. The consistency of the oleogels increased with the increasing amount of FFAs and HCs and the decreasing amount of WEs and FALs. The presence of more WEs results in a strong but brittle gel with a high initial flow yield stress. We believe these results might be useful in selecting the right waxes to combine in certain fat-based food products.

High internal phase emulsions stabilized solely by whey protein isolate-low methoxyl pectin complexes: effect of pH and polymer concentration.

In recent years, there has been significant progress in edible emulsion technology especially with respect to creating and stabilizing surfactant-free emulsion systems for food applications. In this paper, we demonstrate the fabrication of high internal phase emulsions (HIPE) (φoil = 0.82) stabilized using colloidal complexes of non-gelling biopolymers (at concentrations as low as 0.3 wt%). The colloidal complexes were pre-formed by combining whey protein isolate (WPI) and low-methoxyl pectin (LMP) at three different pH values (i.e. pH 3.5, 4.5, 5.5) and used further for fabricating stable HIPEs. In addition to the effect of pH, the influence of total biopolymer concentration on the formation and properties of HIPEs was also evaluated. Depending on the total concentration of biopolymers used, the WPI-LMP complexes (formed at pH 4.5) showed a Z-average diameter in the range of 250-350 nm. It was found that the formation of HIPEs was strongly influenced by the pH of the colloidal complexes. At a pH close to the isoelectric point of WPI (≈pH 4.8) and WPI-LMP complexes (≈pH 3.4), severe aggregation of colloidal particles occurred, resulting in poor formation and stability of HIPEs. On comparing the stabilization behaviour of the complexes with the uncomplexed protein, it was noticed that the former provided comparatively better stabilization to the HIPEs against coalescence at pH 4.5 and 5.5. Based on the rheological data (low amplitude oscillatory shear rheology and flow measurements), all HIPE samples showed viscoelastic and shear-thinning behaviour. We believe that such viscoelastic gel-like systems could find potential commercial applications in the development of label-friendly novel food products with interesting textures.

Edible oil structuring: an overview and recent updates.

In recent years, research dealing with edible oil structuring has received considerable interest from scientific community working in the area of food formulation. Much of this interest is linked to the possibility of using structured oil in development of newer product formats with improved nutritional profile (trans fat-free, low in saturated fats and high in mono and/or poly unsaturated fatty acids). In addition to the obvious industrial need of finding the alternative formulation approach, the interesting properties of structured systems (particularly, oleogels) also makes them a fascinating subject for fundamental studies. In this paper, we attempt to give a comprehensive and concise overview of the field of oil structuring with special emphasis on the updates from recent years. Specifically, several categories of food-grade oleogelators and their potential food applications are summarized with typical examples along with a discussion on the general principles and unresolved challenges related to this emerging area.

The Contribution of Modern Margarine and Fat Spreads to Dietary Fat Intake.

The study of dietary fat consumption and its resultant effects on human health has been one of the most investigated topics in the field of human nutrition. Based on the results obtained from such studies, specific dietary recommendations on fat intake (both in terms of quantity and quality) have been established by health organizations around the globe. Among the various food industry sectors, the margarine manufacturers have also responded to these guidelines and now offer improved formulations with a desirable balance of fat contents and fat types. The main aim of this article is to provide an overview on how these modern margarines can contribute towards reaching the dietary guidelines relating to fat intake. In particular, the dietary recommendations with respect to the specific fatty acid types are comprehensively detailed along with an emphasis on the role of modern margarines in providing balanced fat types (more polyunsaturated fats, less saturated fats and a near-complete absence of trans fats) in the daily diet.

Rheological profiling of organogels prepared at critical gelling concentrations of natural waxes in a triacylglycerol solvent.

The aim of this study was to use a detailed rheological characterization to gain new insights into the gelation behavior of natural waxes. To make a comprehensive case, six natural waxes (differing in the relative proportion of chemical components: hydrocarbons, fatty alcohols, fatty acids, and wax esters) were selected as organogelators to gel high-oleic sunflower oil. Flow and dynamic rheological properties of organogels prepared at critical gelling concentrations (Cg) of waxes were studied and compared using drag (stress ramp and steady flow) and oscillatory shear (stress and frequency sweeps) tests. Although, none of the organogels satisfied the rheological definition of a "strong gel" (G″/G' (ω) ≤ 0.1), on comparing the samples, the strongest gel (highest critical stress and dynamic, apparent, and static yield stresses) was obtained not with wax containing the highest proportion of wax esters alone (sunflower wax, SFW) but with wax containing wax esters along with a higher proportion of fatty alcohols (carnauba wax, CRW) although at a comparatively higher Cg (4%wt for latter compared to 0.5%wt for former). As expected, gel formation by waxes containing a high proportion of lower melting fatty acids (berry, BW, and fruit wax, FW) required a comparatively higher Cg (6 and 7%wt, respectively), and in addition, these gels showed the lowest values for plateau elastic modulus (G'LVR) and a prominent crossover point at higher frequency. The gelation temperatures (TG'=G″) for all the studied gels were lower than room temperature, except for SFW and CRW. The yielding-type behavior of gels was evident, with most gels showing strong shear sensitivity and a weak thixotropic recovery. The rheological behavior was combined with the results of thermal analysis and microstructure studies (optical, polarized, and cryo-scanning electron microscopy) to explain the gelation properties of these waxes.

Comparative evaluation of structured oil systems: Shellac oleogel, HPMC oleogel, and HIPE gel.

In lipid-based food products, fat crystals are used as building blocks for creating a crystalline network that can trap liquid oil into a 3D gel-like structure which in turn is responsible for the desirable mouth feel and texture properties of the food products. However, the recent ban on the use of trans-fat in the US, coupled with the increasing concerns about the negative health effects of saturated fat consumption, has resulted in an increased interest in the area of identifying alternative ways of structuring edible oils using non-fat-based building blocks. In this paper, we give a brief account of three alternative approaches where oil structuring was carried out using wax crystals (shellac), polymer strands (hydrophilic cellulose derivative), and emulsion droplets as structurants. These building blocks resulted in three different types of oleogels that showed distinct rheological properties and temperature functionalities. The three approaches are compared in terms of the preparation process (ease of processing), properties of the formed systems (microstructure, rheological gel strength, temperature response, effect of water incorporation, and thixotropic recovery), functionality, and associated limitations of the structured systems. The comparative evaluation is made such that the new researchers starting their work in the area of oil structuring can use this discussion as a general guideline. PRACTICAL APPLICATIONS: Various aspects of oil binding for three different building blocks were studied in this work. The practical significance of this study includes (i) information on the preparation process and the concentrations of structuring agents required for efficient gelation and (ii) information on the behavior of oleogels to temperature, applied shear, and presence of water. This information can be very useful for selecting the type of structuring agents keeping the final applications in mind. For detailed information on the actual edible applications (bakery, chocolate, and spreads) which are based on the oleogel systems described in this manuscript, the readers are advised to refer our recent papers published elsewhere. (Food & Function 2014, 5, 645-652 and Food & Function 2014, 5, 2833-2841).

Biopolymer-based structuring of liquid oil into soft solids and oleogels using water-continuous emulsions as templates.

Physical trapping of a hydrophobic liquid oil in a matrix of water-soluble biopolymers was achieved using a facile two-step process by first formulating a surfactant-free oil-in-water emulsion stabilized by biopolymers (a protein and a polysaccharide) followed by complete removal of the water phase (by either high- or low-temperature drying of the emulsion) resulting in structured solid systems containing a high concentration of liquid oil (above 97 wt %). The microstructure of these systems was revealed by confocal and cryo-scanning electron microscopy, and the effect of biopolymer concentrations on the consistency of emulsions as well as the dried product was evaluated using a combination of small-amplitude oscillatory shear rheometry and large deformation fracture studies. The oleogel prepared by shearing the dried product showed a high gel strength as well as a certain degree of thixotropic recovery even at high temperatures. Moreover, the reversibility of the process was demonstrated by shearing the dried product in the presence of water to obtain reconstituted emulsions with rheological properties comparable to those of the fresh emulsion.

Edible oleogels based on water soluble food polymers: preparation, characterization and potential application.

Oil structuring using food-approved polymers is an emerging strategy and holds significant promise in the area of food and nutrition. In the current study, edible oleogels (containing >97 wt% of sunflower oil) were prepared using a combination of water soluble food polymers (methylcellulose and xanthan gum) and further evaluated for potential application as a shortening alternative. Microstructure studies (including cryo-SEM) and rheology measurements were conducted to gain more insights into the properties of these new types of oleogels. In addition, the functionality of oleogel as a shortening alternative was studied in terms of batter properties and the texture analysis of cakes and compared to the reference batches made using either oil, commercial shortening or cake margarine. Interestingly, while the batter properties (air incorporation, rheology and microstructure) of the oleogel batch were more close to the oil batch, the textural properties of cakes were significantly better than oil and resembled more to the cakes prepared using shortening and margarine.

Polysaccharide-based oleogels prepared with an emulsion-templated approach.

The preparation and characterization of oleogels structured by using a combination of a surface-active and a non-surface-active polysaccharide through an emulsion-templated approach is reported. Specifically, the oleogels were prepared by first formulating a concentrated oil-in-water emulsion, stabilized with a combination of cellulose derivatives and xanthan gum, followed by the selective evaporation of the continuous water phase to drive the network formation, resulting in an oleogel with a unique microstructure and interesting rheological properties, including a high gel strength, G'>4000 Pa, shear sensitivity, good thixotropic recovery, and good thermostability.

Edible applications of shellac oleogels: spreads, chocolate paste and cakes.

We demonstrate three potential edible applications of shellac oleogels as (i) a continuous oil phase for preparation of emulsifier-free, structured w/o emulsions (spreads), (ii) a replacer for oil-binders in chocolate paste formulations and (iii) a shortening alternative for cake preparation. Water-in-oil emulsions with up to 60 wt% water were prepared without the need for an emulsifier by simply using shellac oleogels as the continuous oil phase. The water droplets in these emulsions (size < 40 µm) were stabilized via interfacial and bulk crystallization of shellac. Chocolate paste prepared by complete replacement of an oil-binder and a partial replacement of palm oil (∼27%) with a shellac oleogel, showed no sign of 'oiling-out' when stored at elevated temperature (30 °C) for several weeks. Further, cakes prepared using oleogel-based w/o emulsions (20 wt% water) as a shortening alternative showed comparable functionalities (texture and sensory attributes) to the standard cake.