Physicochemical Characteristics,Emulsifying Performance,and Potential Application Of Insoluble Soybean Fiber(ISF) Extracted By Homogenization Associated With Alkaline Treatment

Defatted okara is rich in insoluble soybean fiber(ISF)with strong hydrophilicity,resulting in large potential in food industry.However,the components inside okara are tightly combined with each other,resulting in both huge difficulty during processing and low utilization at current situation.This dissertation have systematically explored the physicochemical and emulsifying properties of ISF extracted from defatted okara with different extracting methods(i.e.,alkaline treatment,AK;homogenization followed by alkaline treatment,HA;alkaline treatment followed by homogenization,AH),and comparatively analyzed the effects of special pretreatments(i.e.,acidification,salinization,heating)on the basic characteristics and freeze-thaw stability of ISF-based concentrated emulsions.Specific ISF was selected to prepare whipped cream so as to widen the application basis of fiber-based emulsions and to provide new opportunities and ideas for the high-value utilization of ISF.The processing methods of defatted okara have significantly affected the physicochemical and emulsifying properties of ISF.The residual protein inside the ISF was effectively removed(p<0.05),and the ISF structure was loosened through the alkaline treatment.Among them,the ISF extracted at a lower pH(7?9)contained more residual protein,and the prepared emulsions possessed smaller droplet size but poor stability.The emulsions prepared by ISF extracted at higher pH(11?12)displayed better stability due to stronger electrostatic repulsion,steric hindrance,and weak gel network structure.A smaller size,looser structure,and stronger interaction between ISF particles were identified in the ISF extracted via high-intensity homogenization(3 passes at 300 bar,and 1 or 3 passes at 400 bar),while a narrower droplet size distribution,higher apparent viscosity and elastic modulus,as well as better centrifugal stability and salt resistance,were observed in the ISF-emulsions prepared by above mentioned ISF.The homogenization treatment effectively inhibited the sedimentation of the ISF-emulsions during 120 d storage.Among them,the ISF extracted by"pH12 treatment followed by homogenization(labeled as AH-ISF)"demonstrated better capacities to form ISF-emulsions with higher stability.The interactions between ISF particles could be regulated by both the homogenization of defatted okara and the special pretreatment of ISF,thereby affecting the formation and stability of ISF-based concentrated emulsions.Higher-strength homogenization endowed the AH-ISF-based concentrated emulsions with the lower absolute value of ?-potential and d_4,3,higher apparent viscosity and elastic modulus,leading to better resistance to oil precipitation caused by high-speed centrifugation and creaming during long-term storage as well as stronger stability towards special environment of either acid,or salt,or heating.The concentrated emulsions prepared by the ISF subjected to salinization pretreatment by adding 100 mM NaCl presented the largest droplet size and the lowest apparent viscosity,which were extremely unstable.The concentrated emulsions prepared with the ISF subjected to heating pretreatment of 85? exhibited the smallest droplet size,the highest apparent viscosity,and the strongest viscoelastic characteristics with higher stability.Acidic pretreatment by adjusting pH to 5 slightly improved the characteristics of concentrated emulsions prepared by single alkaline-extracted ISF but partially weakened the stability of AH-ISF concentrated emulsions.Particularly,the secondary emulsification further reduced the droplet size of the freeze-thaw ISF concentrated emulsions and strengthened the rheological properties of these emulsions.The homogenization during the extraction of ISF effectively suppressed the negative impact of the weakening electrostatic repulsion on emulsion instability and strengthened the stabilizing effect of the gel network structure on ISF concentrated emulsions.ISF can be used to prepare whipped cream by partially replacing hydroxypropyl methylcellulose(HPMC)with self-made ISF in present research.As the proportion of AH-ISF increases,the absolute value of?-potential,and the foaming performance of the mixed dispersions increased.Both the absolute value of?-potential and the droplet size of the O/W emulsions increased,whereas the apparent viscosity decreased.The overrun,foam stability,cream stability,elastic modulus,and complex viscosity of whipped cream first increased and then decreased,while the loss angle first decreased and then increased,indicating that ISF partially improved the network structure of cream,thereby enhancing the stability performance of foam and whipped cream.