Construction Of Pickering Emulsion Systems With Bamboo Fungus Protein And Application

High Internal Phase Pickering Emulsion(HIPPE)is a highly concentrated emulsion stabilized by solid particles with a volume fraction of dispersed phase >74%.Due to the diverse sources of raw materials,stable structure and adjustable structural properties,HIPPE provides a wider application field and advantages compared with traditional emulsions.HIPPE exhibits great potentials in the fields of foods,pharmaceuticals,materials and cosmetics.Significant progress has been made in the development of high quality HIPPE stabilizers with biocompatible proteins as raw materials,and the variety and range of available proteins are expanding.Currently,plant and animal proteins are mainly chosen as raw materials for studies,however,fungus,as another type of protein source in nature,has never been discovered for its potential application as HIPPE stabilizer.Therefore,in this paper,an edible fungus,bamboo fungus,was selected as the research object,the proteins extracted was used to prepare HIPPE stabilizer.Subsequently,the structural properties and the stabilization mechanism were investigated,and the feasibility of fungi proteins as HIPPE stabilizers was confirmed.Furthermore,the HIPPE system was used to deliver Antarctic krill oil(KO),the aim was to modify KO solubility,texture,digestibility,and stability features so as to increase the application form of KO products.Finally,the safety and functional activities of HIPPE delivered KO products were studied through cellular and animal experiments,and the feasibility and prospect of their application in the field of food and medicine are proved.The main research contents and conclusions of this paper were as follows.(1)Bamboo fungus proteins were obtained by alkaline extraction and acid precipitation combined with dialysis treatment with a purity of 78.74%,and bamboo fungus protein gel particles(BGPs)were successfully prepared by TG enzyme cross-linking method.As p H increased,the particle size of BGPs decreased and the absolute ζ-potential value increased.p H 3,9 and 11,the contact angles of BGPs were76.6°,75.8° and 77.6°,respectively,which had the potential to be used as O/W HIPPE stabilizers.The α-helix content in BGPs was negatively correlated with hydrophobicity,and the β-sheet and random coil content was positively correlated with hydrophobicity.Under the above p H conditions,BGPs exposed more free sulfhydryl groups and internal hydrophobic groups,leading to their increased hydrophobicity and larger contact angles.At p H 3,hydrogen bonding and hydrophobic interactions were the main forces for the formation and stabilization of BGPs,while at p H 11,electrostatic interactions played a dominant role.(2)HIPPE was prepared by a one-step homogenization method using BGPs as stabilizer and isooctane as oil phase.Because of the effect of p H on the hydrophobicity of BGPs,semisolid gel-like HIPPE(φ = 80%)was prepared at p H 3,9and 11.The HIPPE droplets were regular spherical shape,with multiple layers of droplets in contact with each other and closely packed.The interfacial films and three-dimensional network structure composed of BGPs contribute to HIPPE stability.The increase of p H led to increase the electrostatic repulsion of emulsions,and the HIPPE droplet diameter decreased from 25.56 μm to 15.85 μm,making the particle size distribution homogeneous.The above semisolid gell-like HIPPE can storage at4℃ for 5 months with excellent stability.(3)After mixing KO with soybean oil as the oil phase,KO-HIPPE(φ = 80%)was prepared with BGPs as the stabilizer.In the same conditions,the electrostatic effect was stronger at p H 11,and it was easier to form stable KO-HIPPE with a particle size of about 1 μm.Excessive stabilizer(2%)promoted flocculation and aggregation of droplets.KO-HIPPE exhibited good storage stability.The particle size of KO-HIPPE increased slightly after simulated oral digestion,flocculation and coalescence occurred after simulated gastric digestion,and finally turned into small droplets by the action of enzymes and other substances.Compared to the oil phase,KO-HIPPE displayed more rapid and complete FFA digestion and release properties.(4)RAW 264.7 cells were used to assess KO-HIPPE toxicity,at 0.25 mg/m L,the cell survival rate of the oil phase was 58.25% whereas KO-HIPPE was 90.69%.At higher concentrations(0.5-1 mg/m L),cell survival rate for oil phase treatment was only 9.70%,while KO-HIPPE was higher than 70%.The LPS stimulated RAW 264.7cells were used to establish an inflammation model,and the inhibition of inflammatory mediator NO by 0.25 mg/m L KO-HIPPE was 32.84%,which demonstrated that KO-HIPPE was safety and has anti-inflammatory activity.(5)Ulcerative colitis model of C57BL/6 mice was established by DSS induction,after gavage of KO-HIPPE on the mice,the treatment alleviated the weight loss and elevated DAI score,improving the disease symptoms.Further studies indicated that KO-HIPPE enabled to reduce oxidative stress,decrease MDA levels and increase SOD and GSH in colon tissue,while reducing the levels of pro-inflammatory factors TNF-α and IL-6 in blood.