| Interactions between food hydrocolloids,like polysaccharides and proteins,play an important role in emulsifying capacity,gelling and filming properties of products during the food processing.There are two main problems should be solved urgently.One is to build up the exact relationship between interactions among hydrocolloids and final qualities of products,such as stability,textural properties,and flavor controlled release.The other is to make use of nanotechnology to produce effective strategies for the formulation of a healthier diet with optimized bioavailability of the most desirable ingredients.Meanwhile,the exploitation of protein-polysaccharide interactions offers opportunities for the design of new ingredients and interfacial structures with applications in the food and pharmaceutical industries.In the present work,we aimed to understand the interaction among polysaccharides,proteins and polyphenols in the aqueous solution and to utilize in forming new food formulations.Konjac glucomannan(KGM),gelatin and tannic acid were chosen to be studied model.1.Effects of biopolymers' concentrations on phase transition and microstructure of KGM and gelatin mixturesPhase transition of compatibility to separation in gelatin and KGM mixtures was investigated with the increase of biopolymers' concentrations.This type of phase separation was totally depended on biopolymers' concentration.To fix the KGM concentration at 0.4wt% and to increase the gelatin concentration gradually,phase transition experienced two stages: miscibility(Cgelatin 0~2wt%)and protein-continuous separation status(Cgelatin >2wt%).Changes of micro-networks during phase transition were studied using small-angle X-ray scattering(SAXS)measurement,rheology,and fluorescence microscope.The results straightforwardly revealed that network architectures became tight in miscibility status due to strong interactions between proteins and polysaccharides.After phase separated,gelatin-labeled fluorescence images visualized the process of network transited from polysaccharide to protein.2.Effects of external conditions(ionic strength,pH and temperature)on phase transition of KGM and gelatin mixturesEffects of external conditions on phase diagram,phase boundary and microstructuresof KGM and gelatin mixtures were investigated.With the increase of ionic strength,phase separation was accelerated due to promoting of protein aggregations.In the alkaline condition,deacetylation of KGM would induce its self-aggregation because of strong hydrophobic interaction.Network formed by deacetylated KGM excluded gelatin molecular into another phase,which promoted phase separation.Higher temperature enhanced deacetylation of KGM and induced phase separation.However,lower temperature,especially below the gelling point of gelatin,phase separation would be inhibited due to gelation of gelatin.3.Effects of molecular parameters(molecular weight and charge density)on phase transition of KGM and gelatin mixturesMolecular parameters,such as molecular weight and charge density,also affected the phase behavior of KGM and gelatin mixtures.Three kinds of degraded KGM were obtained using ?-ray irradiation in ethanol solutions.The molecular weight measured by GPC of degraded KGM samples was 6.552×105Da,6.146×105Da and 4.365×105Da respectively.Results illustrated that the low molecular weight of KGM would increase region of phase compatibility.Carboxymethylated glucomannan(CM-KGM)was modified to get negative charged polysaccharide.The type of phase separation between CM-KGM and gelatin was associative phase separation resulting from electrostatic interaction.4.Coupling process of gelation and phase separation on KGM and gelatin mixturesDuring the cooling of mixtures below to the gelling point of gelatin,coupling process of phase transition and gelation was investigated.When kinetics of macro-phase separation was faster than gelation's,gelatin molecules were gathered in one phase due to depletion interaction and were promoted gelation.When the speed of gelation was faster,gelatin network would block self-aggregation of KGM molecules resulting in a kind of micro-phase separated gel structure.Multiple-particle tracking microrheology was performed to study the coupling process in the micro-scale.It demonstrated that gelation and micro-phase separation all could induce the imhomogenerous of molecular distribution in the microscale.5.Effects of phase status on binding behavior and structure of ternary complexesamong KGM,gelatin and polyphenolEffects of co-exist matrix and their phase status were also influneced structural properties and assembling behavior of polysaccharide-protein-polyphenol ternary complexes.When KGM and gelatin kept phase compatible,they all could bind with tannic acid and form ternary complexes resulting from hydrophobic interaction.Properties of shape,structure,and aggregated ways of soluble or insoluble complexes were investigated using particle size analysis and SAXS measurements.For CM-GM,ternary complexes were formed by encapsulation of tannic acid using CM-GM/gelatin coacervates.Due to benefits of Pickering emulsions,protein-based nanocomplexes have been widely developed to stabilize Pickering emulsions.KGM can regulate particle size and surface wettability of KGM/gelatin/tannic acid self-assembled ternary complexes.Fluorescence microscopy,Cryo-SEM and interfacial rheology were used to study the adsorption behavior at the medium chain tryglerides(MCT)-water interfaces.At the low ternary complexes concentrations(2.5-10 mg/mL),Pickering emulsions formed and stabilized against pH change(1.5-7.5)and 150 mM ionic strength.Except for MCT,the oil phase could change to soybean oil,corn oil and olive oil.In vitro digestion results showed that Pickering emulsions had capacity to control the speed of oil digestion.They are good formulations for encapsulation and controlled delivery of oil soluble nutrients. |
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