Excellent hydration properties and oil holding capacity of citrus fiber: Effects of component variation and microstructure

In this study, the effects of components and microstructure on the water holding capacity (WHC), water swelling capacity (WSC), and oil holding capacity (OHC) of citrus fiber were investigated. Nine citrus fiber samples with various component percentages were prepared by an efficient fiber component separation process. The chemical composition, FT-IR, XRD, TG, WHC, WSC, OHC, particle size distribution, and zeta potential of all samples were determined. It was revealed that citrus fiber samples decreased in particle size and zeta potential, increased in crystallinity, and gradually decreased or even disappeared in the characteristic absorption peaks of hydroxyl groups, lignin, hemicellulose, and pectin with increasing treatment steps, which was consistent with chemical composition. Thermal stability analysis showed that citrus fiber with cellulose as the main component had higher thermal stability. The cellulose and hemicellulose components increased WHC by up to 75.99%, and the cellulose component increased OHC by up to 20.61%. According to SEM and Pearson correlation analysis, WHC and WSC were determined by hemicellulose and cellulose, as well as the microstructure of citrus fiber, while OHC was mainly depended on cellulose and microstructure. It was concluded that the loose and large interstitial structure was the basis for the strong water or oil absorption properties, and the more complete primary wall structure was the prerequisite guarantee of the strong water or oil locking ability.