Study Of Physicochemical,Rheological And Microstructural Properties Of Citrus Fiber Based On High-pressure Homogenization Treatment

Citrus fiber is a kind of natural functional dietary fiber which extracted from citrus peels waste.It not only can be added into food as dietary fiber,but also can be used as oil carrier,emulsifier,thickener.The particle size,microstructure,and molecular structure of citrus fiber changed after high-pressure homogenization treatment which resulted the change of rheological properties,microstructural propreties,and absorbtion properties.Therefore,it was meaningful to study the rheological properties,microstructural propreties and absorbtion properties before and after high-pressure homogenization treatment.The citrus fiber with different particle size(10 ?m,40 ?m and 100 ?m)was treated with high-pressure homogenization under different concentration(0.5%-2.5%).The rheological properties(dynamic rheological properties,nonlinear rheological properties),physicochemisty properties(water holding capacity,oil holding capacity,water binding capacity,and powder flowability),thermal properties,particle size distribution,crystal state,molecular structure before and after high-pressure homogenization treatment were studied.It was found that the high-pressure homogenization treatment could significantly improve the oil holding capacity of citrus fiber(improved by 2.8?6.5 times).Based on this property,the dynamic rheological properties,microstructural properties,and fractal dimension of citrus fiber-oil mixed system were studied.Through the analysis of basical physicochemisty properties of citrus fiber,it was found that the high-pressure homogenization treatment could significantly improve the water holding capacity,water binding capacity and oil holding capacity.But the bulk density decreased after high-pressure homogenization treatment.The ring shear cell tester was used to measure the flowability of citrus fiber,and it was found that the high-pressure homogenization treatment could significantly decrease the flowability and improve the powder cohesion of citrus fiber.At last,the different scanning calorimetry was used to measure the glass-transition temperature of citrus which was reduced dramatically.Through the study of dynamic rheological properties,it was found that the high-pressure homogenization treatment could improve the apparent viscocity and reduce the avtive energy of the system of citrus fiber.Also,it could improve the storage modulus and loss modulus of citrus fiber.The large amplitude oscillation test was applied to measure the viscoelasticity of citrus fiber in nonlinerar viscoelasticity region.It was found that the citrus fiber suspension structure was changed from type I to type ?.The fourier transform rheology method and Chebyshev stress decomposition mehod were applied and it was found than the citrus fiber presented strain-softening behavior.Also,the shear-shinning was changed to shear-thickening behavior after high-pressure homogenization treatment.Through the measurement of pariticle size distribution,it was found that the particle size of citrus fiber was significantly reduced after high-pressure homogenization treatmen.It could be concluded from scanning electronical microscopy measurement that there were two major changes after high-pressure homogenization treatment.Firstly,the globular citrur fiber particle changed to flake like particle which has some branches.Secondly,some pores were formed after the high-pressure homogenization treatment.Through the X-ray diffraction and Fourier Transform Infraed Spectroscopy measurement,we could conclude that a large amount of covalent bond was broken during the high-pressure homogenization treatment.the structure of cellulose,ligin and other composition were broken and the crystal type was changed from type I to type III.Through the rheological propertie measurement of citur fiber-oil mixed system,it was found that the high-pressure homogenization treatment could significantly improve the apparent viscosicty,storage modulus,loss modulus and reduce the active energy of mixed system.It was observed that the microstructure of citrus fiber after high-pressure homogenization treatment was damaged through the result of scanning electronical microscopy measurement,and the oil could improve the number and area of pores on the surface of citrus fiber.The fractal demision was caculated from the image of confocal microscopy,and we can concluded that high-pressure homogenization could improve the degree of chaos of the suspension system and make it more homogeneous.