Dietary Fiber: Fractionation, Characterization and Potential Sources from Defatted Oilseeds

Dietary fiber (DF) has wide applications, especially in the food and pharmaceutical industries due to its health-promoting effects and potential techno-functional properties in developing functional food products. There is a growing interest in studies related to DF; nevertheless, there is less focus on the fractionation and characterization of DF. The characteristics of DF fractions explain their functionality in food products and provide clues to their physiological effects in food and pharmaceutical industrial applications. The review focuses on a brief introduction to DF and methods for its fractionation. It discusses the characterization of DF in terms of structural, physicochemical and rheological properties. The potential sources of DF from selected defatted oilseeds for future studies are highlighted.

Model and optimal operational windows for hydrodynamic fiber fractionation

Based on fitted experimental data, an empirical fractionation model for mini-channel hydrodynamic fiber fractionation (miniFrac) is presented. This model, combined with an optimization procedure, is then used as a design tool to synergize competing fractionation performance characteristics, i. e., product quality, product yield and energy demand. Based on this model, miniFrac is compared to state-of-the-art fiber fractionation technology with respect to (i) long fiber-short fiber fractionation and (ii) fines-fiber fractionation. In terms of fines-fiber fractionation, miniFrac is outperformed by typical micro-hole pressure screening regarding the purity of fines fraction. However, a comparison with a slotted (slot width of 0.2 mm) and a smooth-holed pressure screen (hole diameter of 0.8 mm) shows, that miniFrac is capable of outperforming both systems regarding product quality and energy demand at a comparable product yield. If, in the case of fines-fiber fractionation, reject purity (i. e., fines exclusion) is more important than fines purity (i. e., long fiber remain in the reject), miniFrac is an interesting tool with some key advantages over pressure screens.

Multistage fiber fractionation of softwood chemical pulp through smooth-hole screen cylinders and its effects on paper properties

Pressure screens are used to fractionate fibers on the basis of aspect ratio to obtain high value longfiber rejects and less desirable fines-rich accepts. Fiber fractionation is more practical and of maximum economic and commercial benefits when a mill can make use of all obtained fractions. We have demonstrated the potential of upgrading the reject fraction through a multistage fractionation process of a northern bleached softwood kraft pulp while isolating the remaining low-value pulp to be used as a raw material for a novel fiber-based product. The optimum operating conditions such as volumetric reject ratio, Rv; aperture velocity, Vs; and screen aperture size to carry out efficient fractionation were determined for the screens with 0.5-mm, 0.8-mm, and 1.0-mm apertures. This work shows that a high fines percentage in the accept fraction and increased fiber length in the reject fraction can be obtained when operating the pressure screen at a higher Rv and lower Vs using the screen cylinder with the small aperture size (0.5 mm). Feed and fractionated streams of pulp were used to study the effects on the physical properties of paper. Handsheets were made for strength properties of the unfractionated and fractionated pulps for comparisons. Significant improvements in the physical properties were observed after the removal of fines.

An Evaluation Index of a Hydrocyclone for Softwood Pulp Fiber Fractionation

Fractionation of softwood BCTMP pulp fiber was carried out with a cylindrical hydrocyclone. Pulp fiber length characterization in different streams have been examined using FQA. The fiber length fraction density function f is calculated and the separation index H(L) is used to evaluate fiber fractionation performance for different streams, and its specific expression was formed, so the new index may be widely used in the study of the evaluation of the separation performance of the hydrocyclone.

Recycled Old Corrugated Container Fibers for Wood-Fiber Cement Sheets

Recycled pulp of old corrugated containers (OCCs) was studied as a possible fiber source for wood-fiber cement (WFC) sheets. This industry currently largely relies on kraft pulp, an expensive fiber source. Thus, WFC sheets were made using less costly OCC fibers utilizing various types of treatments including fiber fractionation (FF) and refining to 500 and 400 Canadian Standard Freeness (CSF) to determine the effect of these treatments on the sheets strength. Unprocessed virgin kraft fiber of radiata pine (Pinus radiata) was used as control for comparison purposes. The unprocessed OCC pulp furnish yielded an initial freeness of 635 CSF; after fractionating, however, it was increased to 754 CSF. OCC pulp presented a kappa number of 47, compared to 23.7 for P. radiata. Fractionating OCC pulp was effective in raising the range of long fibers in the stock from 68 percent to 85 percent, before and after fractionating, respectively. Results from WFC sheets made in laboratory showed that there was no significant difference in board strength among boards made with unprocessed OCC fibers, fractionated and refined OCC, and P. radiata fibers. However, sheet strength decreased when refined OCC fibers were used. The results suggest that OCC fibers can produce WFC sheets with desirable characteristics compared to those of unrefined virgin kraft fiber of P. radiata.

Holst Filtration Apparatus for Van Soest Detergent Fiber Analyses

New filtration equipment was developed to improve the acid-detergent method of fiber fractionation. This apparatus incorporates a vacuum manifold with an air metering device that provides the operator very precise control over the partial vacuum, permitting a very gradual change in vacuum level as needed for proper filtration. The partial pressure is provided by a water aspirator. A hot water jacket permits a continuous flow of hot water around the sample during the filtering process to keep the sample hot. This speeds filtering on practically all samples and is essential for reliable results on samples high in carbohydrates and salts. As a result of this new filtration equipment we do not need asbestos for a filter aid. This eliminates the need for duplicate acid-detergent fiber analyses when using 72% H2SO4 for the cellulose and lignin determinations. Six independent analyses were performed on each of 9 samples (3 feces, 3 orts, and 3 feeds) for the determination of acid-detergent fiber and its constituents. The average maximum differences for these analyses indicate that this filtration apparatus and the method are reproducible and have reduced the filtration time from several hours, on some samples, to 15 min.