Understanding the functional properties of citrus fibers as function of biopolymer composition and fruit characteristics
Recent work has demonstrated that the functional properties of citrus fibers can be improved upon application of high pressure homogenization and careful drying. However, the functionalization depends on the various biopolymers and the ratio between them. For instance, a certain amount of pectin needs to be extracted in order to enable the de-fibrillation of the cellulose microfibrils in lemon peels. The resulting suspension shows a yield stress and a strong shear-thinning behavior similar to cellulose-based gels. However, the exact threshold and type of pectin that needs to be removed is still unclear. Moreover, depending on the ratio of pectin to other biopolymers (cellulose, hemicellulose and protein), different functionalities may be achieved. The functionality of the citrus fibers depends on which network dominates the mechanical response. In the absence of a pectin extraction step, the mechanical response is dominated by the pectin network rather than by the cellulose network. The threshold between a pectin-driven behavior and a cellulose-driven behavior is not yet defined. Finally, it is anticipated that the properties of the citrus fiber will vary depending on the degree of maturity, variety and parts of the fruit. It is therefore hypothesized that the quality of the ingredients derived from citrus fibers will also be impacted by the properties of the citrus fruits.