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Proteins, polysaccharides and their blends, as examples of natural biopolymers, may be considered as amphiphilic macromolecules that play an essential role in stabilizing food formulations (foams, emulsions and dispersions). Under specific compositions and conditions (protein-to-polysaccharide ratio, pH, ionic strength, temperature, mixing, processing steps) proteins and polysaccharides form water-soluble hybrids (complexes or conjugates), but not coacervates, with enhanced functional properties in comparison to the proteins and polysaccharides alone. Aqueous mixtures of WPI (4–10 wt%) and xanthan gum (>0.5 wt%) form clear aqueous systems exhibiting new physicochemical properties such as rheological behavior, surface properties, surface density of charge (zeta potential), surface hydrophobicity and diffusion behavior. Electrostatic interactions and thermodynamic incompatibility in mixed biopolymer solutions were correlated to the functional properties (rheology, surface properties and surface hydrophobicity) of these adducts. Evidences for associative interactions between WPI and xanthan gum have been established by studying the rheological behavior, the surface hydrophobicity and the surface dynamic properties of the blends. The electrostatic and hydrophobic interactions form hybrids that can provide a synergistic effect on the emulsifying capabilities of the biopolymers and can increase the stability of emulsion droplets against coalescence and flocculation.

Protein/polysaccharide conjugates were used to stabilize oil-in-water (O/W) emulsions and oil-in-water-in-oil (O/W/O) double emulsions. By properly selecting the type of protein (WPI) and the polysaccharide (xanthan gum, fenugreek gum), and by using specific ratios of the two biopolymers and their solution concentrations, amphiphilic biopolymer adducts were formed. A synergism in the emulsification properties was observed in WPI/polysaccharide conjugates compared to each of the biopolymers alone. Submicron droplets of oil-in-water were obtained by applying a high-pressure homogenization process during the first step of the double emulsion preparation. It was also demonstrated that double-emulsion globules could be formed with a very high yield of addendum entrapment (above 95%) during the second step of the emulsification process. The differentiation between the two types of oils, O1 (the inner) and O2 (the outer), in the double emulsions enabled high entrapment capacity of the addendum in the inner oil phase. In addition, when the inner oil phase (O1) was a 1:1 (w/w) mixture of MCT/triacetin and the external oil phase (O2) was a silicone oil, it was possible to slow the release of the entrapped matter while the solubility of the inner phase in the external oil phase remained constant. The addendum solubility in the external oil phase was not a limiting factor in the release process. The presence of hydrophobic additives (i.e., 1 wt.% glycerol monooleate) in the inner oil phase helped to better control the transport to the external oil phase. In the best case, the addendum leakage to the external oil phase was only ca. 0.2 wt.% during a period of 28 days at 25 °C. WPI/xanthan gum adducts served as thick and efficient barriers against release of flumethrin® (a veterinary drug model) entrapped in the core of the O/W/O multiple globules.

A synergism in the emulsification properties was seen in WPI/polysaccharide complexes in comparison to each of the biopolymers alone and it was found also to depend on surface properties of the complexes that is strongly affected by the WPI/polysaccharide ratio. It was also demonstrated that the galactose/mannose ratio and the overall number of galactose residues available on the polysaccharide surface, increasing with the molecular weight of the molecule, strongly influence the surface properties of the blend. At pH below the isoelectric point of WPI/xanthan gum, an increase in the thermal stability of the complex was observed and was attributed to strong interactions existing between the biopolymer molecules. These adducts served also as thick and efficient barriers against release of Vitamin B1 entrapped in the core of the W/O/W multiple globules.

Water-in-oil-in-water (W/O/W) double emulsions with improved stability and less polydispersity in droplet size distribution were prepared using polyglycerol polyricinoleate (PGPR) as emulsifier in the inner aqueous phase and replacing the common nonionic hydrophilic monomeric emulsifiers by a “protein–polysaccharide hybrid” in the outer interface. Amphiphilic macromolecular hybrids with specific interfacial recognition capabilities to be termed “biomacro-molecular-recognition hybrids” have been prepared in aqueous solution by interacting whey protein isolate (WPI) with hydrocolloids (xanthan gum, galactomannans) at selected pH and weight ratios. The binary aqueous mixtures do not coacervate or precipitate but form stable molecular adducts. At pH lower than the isoelectric point of the protein (pH 4.6), the yield of encapsulation of glucose (a model marker) in the inner phase of the double emulsion is close to 95%. The emulsion droplets are stabilized by both steric and electrostatic contributions (zeta potential is close to +30 mV). Rheological measurements indicate that, at low pH, such systems behave as viscous ones with G″ (loss modulus) greater than G′ (storage modulus). When the pH is close or greater than the isoelectric point of the protein, the system exhibits a more pronounced elastic behavior (G′

Proteins, polysaccharides and their blends, as examples of natural biopolymers, are surface active materials. Biopolymers may be considered as amphiphilic macromolecules that play an essential role in stabilizing food formulations (foams, emulsions and dispersions). Under specific conditions (such as protein-to-polysaccharide ratio, pH, ionic strength, temperature, mixing processing), it has been stated that proteins and polysaccharides form hybrids (complexes) with enhanced functional properties in comparison to the proteins and polysaccharides alone. Different protein-polysaccharide pairs are reviewed with particular attention to the emulsification capability of their mixtures. In the case of uncomplexed blends of biopolymers, competitive adsorption onto hydrophobic surfaces is generally reported. Conversely, electrostatic complexation between oppositely charged proteins and polysaccharides allows better anchoring of the new-formed macro-molecular amphiphile onto oil-water interfaces. Moreover,...

Mixtures of polyols (glycerol, propylene glycol, glucose) and water were emulsified in oil (isopropyl myristate (IPM), medium chain triglycerides (MCT), long chain triglycerides (LCT), and d-limonene) under elevated pressures and homogenization, in the presence of polyglycerol polyricinoleate (PGPR), glycerol monooleate (GMO), and their mixture as emulsifiers to form water-in-oil emulsions. High pressures was applied to: a) the emulsion, b) the aqueous phase and c) the oil phase in the presence of the emulsifiers (PGPR and GMO). Under optimal pressure (2000 atms) applied to the ready-made emulsion or to the aqueous phase prior to its emulsification, and with optimal composition (30wt% polyol in the aqueous phase and MCT as the oil phase), the aqueous droplets were stable for months and submicron in size (0.1 μm). Moreover, due to equalization of the oil and the aqueous phases refractive indices, the emulsions were almost transparent. Pressure and polyols have synergistic effects on the emulsions stability...

The regioselective transfer hydrogenation of a carbon−carbon double bond of different chlorobenzylidene ketones is effectuated in ethylene glycol with a very high selectivity in the presence of hom...

Two techniques for extraction and purification were excersized in order to obtain a purified saponins extract from several sources (fenugreek, soybean, locust bean and sesame). The results indicate that fenugreek steroid saponins extract has the best surface properties and reduces the surface tension to 33.3 mN/m and the tetradecane-water interfacial tension from 44 mN/m to 7.5 mN/m. The HLB value was evaluated and found to be 18. Three different types of oil (n-tetradecane, soybean oil, tricaprylin) were emulsified with a 6 wt% aqueous solution of saponins to give an average droplet size of 0.7 μm (yet stable after month). An effective synergism is seen when these emulsions were prepared with sucrose fatty acid esters as co-surfactant. Furthermore, the foaming power was evaluated.