Construction And Mechanism Of Thermally Promoting Stable Pickering Emulsion And Its Application In The Isomerization Of Encapsulated Lycopene

Pickering emulsions are biocompatible and highly stable and are often used in food bioactive component encapsulation systems.However,emulsions are thermodynamically unstable systems and can become unstable and even break under high-temperature conditions.The poor thermal stability of emulsion systems limits their application in many areas,such as heat sterilization and preservation of protein emulsions,heat treatment sessions in processing,and the need for thermal induction of some active substances.Lycopene has activities such as antioxidant,cardiovascular disease risk reduction,reduction of genetic damage,and inhibition of tumorigenesis and development.However,its poor water solubility and susceptibility to oxidative decomposition have limited its use in the food industry.At the same time,there are numerous isomers of lycopene,and cis-isomers induced by heat are required to improve its bioavailability in humans.To address these issues,this study constructs an emulsion thermogenic stabilization strategy based on the heat-induced gelation properties of myofibrillar protein.Firstly,we designed and constructed a stable myofibrillar protein microgel Pickering emulsion system by investigating the effects of particle properties,ionic strength,and oil phase-type on the Pickering emulsion.On this basis,the effect and mechanism of heat-promoted stabilization of the emulsions were investigated and used in the isomerization of the lycopene encapsulation system to enhance the protection rate and bioavailability of lycopene.The main findings of the study are as follows.1.Stable Pickering emulsion systems for myofibrillar protein microgels were designed and constructedFirstly,microgel nanoparticles with different particle characteristics were prepared by controlling the cycle of high-pressure microfluidic,and the effect of particle characteristics on emulsification and emulsion stability was investigated.The results showed that the particles treated with 20 cycles of high-pressure microfluidic(MMP-20)had the best emulsification and emulsion stability.Specifically,MMP-20 has a particle size of approximately 130 nm,a three-phase contact angle of 88.5°,good amphiphilicity,and can quickly diffuse into the oilwater interface to complete the permeation rearrangement;the prepared emulsion has a small droplet size,low flocculation,and good emulsion stability,and is a typical Pickering emulsion stabilizer.Based on the salt solubility properties of myofibrillar protein,the effects and mechanisms of different ionic strengths(0-1000 m M)on the emulsification and emulsion stability of MMP were investigated.The results showed that as the ionic strength increased,MMP underwent electrostatic screening,and emulsification and emulsion stability were significantly enhanced.Specifically,the droplet size of the emulsion decreased significantly from 42.4 μm to 23.8 μm with increasing ionic strength(P < 0.05),and the interfacial pressure increased,indicating that the emulsification of MMP improved and the emulsion stability increased.At the same time,MMP rearrangement at the emulsion interface was significantly enhanced at high ionic strength,and rheological and electron microscopic results showed that the interface formed a more dense network structure than the salt-free system.It resulted in a significant increase in the freeze-thaw stability of the emulsion.The effect of different oil phase types on the stability of MMP emulsions was investigated.The results showed that oil phases with low saturation and high content of short-chain fatty acids were more suitable for MMP emulsions.Specifically,the sequence of emulsion suitability among the selected oil phases was: sunflower oil > soybean oil = rapeseed oil =corn oil = olive oil > coconut oil > palm oil > peanut oil.The sunflower oil emulsion had the smallest droplet size,the highest energy storage modulus in the frequency scan mode,and could stabilize the emulsion at low particle concentrations(0.05%).The peanut and palm oil emulsions had large droplet sizes,low energy storage modulus,and poor emulsion stability.The influence of the macroscopic properties of the oil phase(interfacial tension,viscosity,and density)on the emulsification properties were further investigated and it was found that the viscosity of the oil phase had the most significant influence on the emulsification properties and the lower the viscosity of the oil phase the better the stability of the MMP emulsions.Fatty acid analysis of the oil phase showed that oil phases with low saturation and high short-chain fatty acid content had low viscosity and the MMP emulsions were better adapted for processing.2.To clarify the law of the effect of heating on the properties of MMP emulsions and its heatpromoted stabilization mechanismBased on a stable myofibrillar protein microgel Pickering emulsion system(MMP-20 as the emulsion stabilizer,salt ion strength of 1000 m M in the aqueous phase,sunflower oil as the oil phase,the proportion of oil phase is 75%),the changing pattern of emulsion properties under different heating intensities was investigated.The results showed that the energy storage modulus of the emulsions all remained elevated during the heating up and then cooling down processes;the droplet size of the emulsions remained stable after the heating treatment above 100℃,and the freeze-thaw and centrifugal stability were both improved,indicating that the heat treatment had a significant contribution to the emulsion stability.To further investigate the stabilization mechanism,heating led to the enhancement of MMP hydrophobic interactions at the emulsion interface and the gradual formation of a laminar network structure,resulting in a gradual increase in the interfacial expansion modulus(from4.6 to 8.1 m N/m)and the formation of a high strength elastic film,which in turn led to an increase in emulsion stability.3.The construction of a thermally stable lycopene emulsion embedding system can enhance the bioavailability of lycopene by thermally inducing lycopene isomerization.Based on the exclusive thermal stability of MMP emulsions,lycopene was embedded in emulsion systems,and the effects of emulsion embedding systems on lycopene stability and bioavailability were investigated.The results showed that the retention of lycopene(from 40%to 86%)was significantly improved by encapsulating lycopene in the emulsion system.The emulsion remained stable after heating,and the cis-conformation ratio of lycopene was increased by more than triple;the bioavailability of lycopene in the in vitro gastrointestinal tract was increased from 7.9 to 18.7,indicating that the heat-stabilized Pickering emulsion significantly improved the stability,cis-conformation ratio,and bioavailability of lycopene.