Effect of high-pressure homogenization on the flow properties of citrus peel fibers

In this study, high-pressure homogenization process with two different pressures (90 MPa/13,000 psi and 160 Mpa/23,000 psi) was used to pretreat the citrus peels fiber. Soybean oil was added to the citrus peels fiber before high-pressure homogenization process, and the effect of four different percentages (0, 50%, 150%, and 300%) of oil to fiber on behaviors and physical properties were measured. Shear cell technique was used to measure the flowability index and powder cohesion of these powder samples. The physical properties, including particle size in suspension liquid, bulk density and scanning electron microscopy images of powder were also measured to ascertain the relationship between the structural changes and the flow property variation. The results show that the high-pressure homogenization process can change the granular structures and produce large quantities of tiny pores on the surface of the citrus fiber. Meanwhile, the particle size in suspension liquid and bulk density of powder decreased after this treatment. With the increase of the ratios of oil to fiber, the flowability index decreased and the powder cohesion increased. For the physical properties, the bulk density improved and the particle size in suspension liquid decreased; simultaneously, the number of pores on the surface of the fiber increased. Altering pressure for the high-pressure homogenization process also change the microstructure and flow properties which presented lower particle size in suspension liquid and higher bulk density. Practical applications: This simple and low cost process can efficiently and effectively improve the physical, chemical, and functional properties of various fibrous materials, including surface area, water holding capacity, texture, viscosity, etc. Therefore, this process can be used to develop new value-added products and ingredients from various agricultural fibrous byproducts, such as fruit peers or pulps, seed coats, straws and leaves, etc. In addition, these new value-added ingredients can still be classified into the clean label category that is highly significant to the quality and healthy food market.