Fabrication Of Fatty Acid Glyceride-Based Oleogels And Its Modulation On Formation And Properties Of Water-in-Oil High Internal Phase Emulsions

Oleogels,are often used as alternatives to traditional plastic fats,as well as carriers for flavor,drugs and liposoluble functional active ingredients due to their semi-solid viscoelasticity and low saturated fatty acids.Fatty acid glycerides,such as monoglyceride(MAG)and diacylglycerol(DAG),are typical crystalline granular gelators,with their efficient gelling capacity,excellent emulsification and high safety,making them one of the most promising gelators.The screen of the concentration and type of fatty acid glycerides can modulate the crystallization behavior and physical properties of oleogels,thereby regulating the performance of oleogel-derived systems.However,there is currently a lack of systematic comparison and research on the gelling behavior of different fatty acid glycerides.On this basis,five common fatty acid glycerides with different chain lengths and saturation degrees were selected to prepare oleogels with soybean oil.The effects of the type and concentration of fatty acid glycerides on the crystallization behavior and physical properties of oleogels were investigated.At the same time,solid oleogels were used as oil phases and polyglycerol polyricinoleate(PGPR)was selected as an emulsifier to prepare water in oil(W/O)high internal phase emulsions(HIPEs)by low-energy emulsification method.The stability mechanism of the emulsions was clarified,and the effects of different types of fatty acid glycerides on the formation of the emulsions were systematically compared.The effects of internal phase composition and whipping on the texture of emulsions were also investigated.Finally,the characteristics of emulsions in oral processing and the feasibility of replacing commercial creams were discussed.The main research contents and results are as follows:1.The effects of fatty acid glycerides on the crystallization behavior and physical properties of oleogels.Five fatty acid glycerides,including glyceryl monostearate(GMS),glyceryl monolaurate(GML),glycerol monocaprylate(GMC),monoolein(GMO)and diolein(GDO)were selected to prepare oleogels by direct dispersion method.The type of fatty acid glycerides that could be used to form oleogels and their onset gelling concentrations were determined.The crystallization behavior and physical properties of oleogels were analyzed.The results indicated that all oleogels formed by saturated fatty acid glycerides(GMS,GML and GMC)exhibited thermally reversible solid-like behavior,while unsaturated fatty acid glycerides(GMO,GDO)could not form solid oleogels even at high concentrations(15 wt%).The onset gelling concentration of GMS and GMC was determined to be 2 wt% while GML was determined to be 4 wt% by the inverted tube method.The analysis of the crystallization behavior of the oleogels manifested that GMS and GMC exhibited β and β’ polymorphism with uniformly distributed needle-like crystals,while GML exhibited α crystals with large fibrous sheet cluster,and the faster cooling rates led to finer crystals.At the same concentration,GMS and GMC oleogels possessed higher crystallinity,oil binding capacity,hardness,thermal stability,and deformation resistance.With the increase of MAG concentration,the crystal network became denser,resulting in higher mechanical properties of oleogels.2.Construction and characterization of MAG oleogels stabilized W/O HIPEs.W/O HIPEs were prepared by low-energy emulsification method with MAG oleogels and PGPR.The effects of MAG type and water phase proportion on the physical properties of W/O HIPEs were investigated.The results illustrated that three MAGs and PGPR could reduce the oil-water interfacial tension,and the order of emulsification ability was PGPR > GMS≈ GMC > GML.W/O HIPEs with 85% aqueous phase content could be stabilized by the synergistic effect of 6 wt% MAG oleogels and 1 wt% PGPR.The emulsifier adsorbed at the interface and the lipid crystals of MAG in the interface and network jointly maintained the stability of the emulsions.The W/O HIPEs prepared with 1 wt% PGPR concentration presented a milky white gel-like structure with uniform particles,contained little bound water and mass free water and possessed certain heat resistance and thixotropic recovery capability.The droplet size decreased while the viscoelasticity increased when the water content increased from 75% to 85%,indicating the water droplets exhibited active filler effects.Compared with GML,GMS and GMC oleogel-based W/O HIPEs exhibited smaller droplet sizes and more interfacial crystallization,resulting in higher heat resistance and anti-deformation.The interfacial crystallization of GMS and GMC increased with the increase of freeze-thaw cycles while the crystallization behavior of GML did not change.After freeze-thaw cycle,the elastic modulus,apparent viscosity and the gel strength of the emulsions decreased slightly,but still possessed similar heat resistance,thixotropy recovery and water distribution as the initial emulsions.3.Study on texture regulation and oral digestion behavior of W/O HIPEs stabilized by MAG oleogels.Sodium chloride(Na Cl),sucrose and guar gum were added to the aqueous phase to study the effects of internal phase composition on the gel properties and physical stability of MAG oleogels-based W/O HIPEs.The effects of whipping and oral processing on the properties of emulsions and the feasibility of replacing commercial creams were also investigated.The results showed that the presence of Na Cl and sucrose in the aqueous phase reduced the droplet size and improved the water holding capacity,viscoelasticity and texture properties of the emulsions,thereby endowing emulsions excellent spreadability,ductility and plasticity.In addition,the emulsions exhibited high storage stability and presented no phase separation within 100 days.Although the addition of guar gum had little effect on the macroscopic and microscopic structure of the emulsions,the mechanical properties of the emulsions could be improved to a certain extent.The application of whipping improved the texture and rheological properties of the emulsions,resulting in better plasticity and rigidity.The emulsions with 5 wt% sucrose and 0.5 wt% Na Cl in the internal phase had the best mechanical properties,and their macroscopic performance was similar to that of commercial creams.The droplet aggregation and non-uniformity of the emulsions occurred during the oral processing,and the size of the droplets increased with the extension of the oral processing time.The apparent viscosity of the emulsions also showed a trend of gradually decreasing with the extension of processing time.