Study On Properties And Morphological Structure Of Citrus Fiber

In this paper,the differences of basic components,physical and chemical properties and structures among AQ-Plus-AQ?Fiber-Star-FS and Normal Fiber-NF three different citrus fibers were systematically studied,and the effects of different treatments,especially high pressure homogenization,on the performance and structure of citrus fibers were discussed.The emulsifying properties of citrus fibers were studied by using the better AQ of the three kinds of citrus fibers,and the concentration of citrus fibers and the quality of oil phase were further discussed.The influence of fraction,pH value,NaCl concentration,storage temperature and high pressure homogenization on the stability of emulsion were studied.The results of the study are as follows:(1)There are some differences in the basic components and physicochemical properties of the AQ?FS and NF.Citrus fiber AQ has higher content of insoluble dietary fiber(IDF),cellulose and hemicellulose;citrus fiber FS has the highest content of soluble dietary fiber(SDF);among the three citrus fibers,AQ has the best physical properties,good water holding capacity,oil holding capacity and expansibility;and the three citrus fibers have similar chemical properties.However,there are some differences in structure,especially in-OH content in some groups.FS-OH content is the highest and the crystallinity is the lowest,while AQ and NH with higher crystallinity have better thermal stability.Scanning electron microscopy(SEM)observation shows that AQ and FS citrus fiber particles are smaller,their structure is looser and their surface area is higher.(2)With the increase of ultrasonic treatment time,the size of the three kinds of citrus fibers decreased gradually,and the apparent viscosity showed an increasing trend.In the 0-5 min treatment process,the absolute Zeta potential of the three kinds of citrus fibers suspension increased significantly with the increase of ultrasonic treatment time.With the further extension of ultrasonic treatment time,the absolute Zeta potential of the three kinds of citrus fibers did not change significantly.(3)The structure and properties of citrus fiber before and after high pressure homogenization treatment were studied.The results showed that compared with the initial citrus fiber(ICF),the high-pressure homogenized citrus fiber(HPH-CF)has similar chemical groups,and its hydration performance is improved significantly;the crystallinity and degradation temperature of HPH-CF are lower than ICF;HPH-CF exhibits a scattered long rod or full granular structure under the microscope,while ICF exhibits a flat sheet;HPH treatment changed the morphology of AQ,FS and NF.Among them,AQ showed a full long rod shape due to its strong water holding capacity,and FS and NF showed finer granularity as a whole.HPH treatment can reduce the size of ICF and increase the Zeta potential absolute value of ICF at HPH;physical energy can destroy the hydrogen bond of ICF,expose more hydrophilic hydroxyl groups,and increase the apparent viscosity of HPH-CF significantly.(4)The effects of citrus fiber concentration,oil phase mass fraction,pH value,NaCl concentration,storage temperature and high pressure homogenization(HPH)on the stability of emulsion were systematically studied.The emulsion showed good stability when the fiber concentration was 2% and the oil phase mass fraction was 25%.Confocal laser scanning showed that citrus fiber emulsion stabilized the emulsion by forming a gelatinous three-dimensional network structure.Citrus fiber emulsion was shear thinning,and the apparent viscosity was less affected by pH value,NaCl concentration and storage temperature.The gel properties were higher at pH4.0 and 6.0,higher NaCl concentration and lower temperature.After high pressure homogenization,the particle size,Zeta potential absolute value,apparent viscosity and viscoelasticity were improved significantly.