To investigate the morphological changes of insoluble fiber and their effects on microbiota modulation, particularly Bacteroides, rice bran insoluble fibers were extruded at different feed moisture levels (E20, E40, and E60). The physicochemical properties and SEM revealed that E20 exhibited the highest water holding capacity and displayed the most fragmented edges. E40 had the highest swelling holding capacity and displayed the most lamellar gaps. E60 showed minimal change in physicochemical properties but had a rough surface. After 48h fermentation, E40 showed the highest levels of Bacteroides and SCFAs. E20 and E60 resulted in a modest increase in Bacteroides abundance. SEM showed that bacteria were attached to fragmented edges, loosened lamellar gaps, and rough surfaces of the extruded insoluble fibers. The results suggested that Bacteroides gained a competitive advantage within the extrusion treatment created structural changes. Extrusion treatment can be used to generate specific niches favorable for Bacteroides.

Recent research has primarily focused on strategies for modifying insoluble dietary fiber (IDF) to enhance its performance and functionality. IDF is obtained from various inexpensive sources and can be manipulated to alter its biological effects, making it possible to revolutionize food processing and nutrition. In this review, multiple IDF modification techniques are thoroughly examined and discussed, with particular emphasis on the resulting changes in the physicochemical properties, biological activities, and microstructure of the fiber. An extensive overview of the practical applications of modified IDF in food processing is provided. Our study aims to raise awareness about the vast possibilities presented by modified IDF and encourage further exploration and utilization of this field in the realm of food production.

Phenolics in bound form extensively exist in cereal dietary fiber, especially insoluble fiber, while their release profile in gastrointestinal tract and contribution to the potential positive effects of dietary fiber in modulating gut microbiota still needs to be disclosed. In this work, the composition of bound phenolics (BPs) in triticale insoluble dietary fiber (TIDF) was studied, and in vitro gastrointestinal digestion as well as colonic fermentation were performed to investigate BPs liberation and their role in regulating intestinal flora of TIDF. It turned out that most BPs were unaccessible in digestion but partly released continuously during fermentation. 16 s rRNA sequencing demonstrated that TIDF possessed prebiotic effects by promoting anti-inflammatory while inhibiting proinflammatory bacteria alongside boosting SCFAs production and antioxidative BPs contributed a lot to these effects. Results indicated that TIDF held capabilities to regulate intestinal flora and BPs were important functional components to the health benefits of cereal dietary fiber.

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Legumes are widely appreciated for their abundant reserves of insoluble dietary fiber, which are characterized by their high fiber content and diverse bioactive compounds. Insoluble dietary fiber in leguminous crops is primarily localized in the structural cell walls and outer integument and exhibits strong hydrophilic properties that enable water absorption and volumetric expansion, resulting in increased food bulk and viscosity. This contributes to enhanced satiety and accelerated gastrointestinal transit. The benefits of legume insoluble dietary fiber extend to its notable antioxidant, anti-inflammatory, and anti-cancer properties, as well as its ability to modulate the composition of the intestinal microbiota, promoting the growth of beneficial bacteria while suppressing the proliferation of harmful pathogens, thereby promoting optimal intestinal health. It is highly valued as a valuable thickening agent, stabilizer, and emulsifier, contributing to the texture and stability of a wide range of food products.

Rice bran was modified by steam explosion (SE) treatment to investigate the impact of different steam pressure (0.4, 0.8, 1.2, 1.6, and 2.0 MPa) with rice bran through 60 mesh and rice bran pulverization (60, 80, and 100 mesh) with the steam pressure of 1.2 MPa on the structure, thermal stability, physicochemical and functional characteristics of insoluble dietary fiber (IDF) extracted from rice bran. IDF with SE treatment from scanning electron microscopy images showed a porous honeycomb structure, and lamellar shape in IDF became obvious with the increase of steam pressure. The relative crystallinity and polymerization degree of crystalline regions in IDF from rice bran with SE treatment from X-ray diffraction analysis were decreased. Differential scanning calorimetry results showed that thermal stability of IDF with SE treatment increased with the increase of crushing degree. The results of FT-IR also suggested that some glycosidic and hydrogen bonds in IDF could be broken, and some cellulose and hemicellulose were degraded during SE process. The physicochemical and functional characteristics of IDF, including water-holding capacity, oil-holding, glucose adsorption capacity, α-amylase and pancreatic lipase inhibition capacity were decreased with the increase of steam pressure and crushing degree. The swelling and nitrite adsorption capacities of IDF were increased first and then decreased with the increase of steam pressure. The physicochemical and functional characteristics of IDF from rice bran were improved after SE treatment, which might provide references for the utilization of IDF from rice bran with SE treatment.

Rosa roxburghii Tratt pomace is rich in insoluble dietary fiber (IDF). This study aimed to investigate the influence of three modification methods on Rosa roxburghii Tratt pomace insoluble dietary fiber (RIDF). The three modified RIDFs, named U-RIDF, C-RIDF, and UC-RIDF, were prepared using ultrasound, cellulase, and a combination of ultrasound and cellulase methods, respectively. The structure, physicochemical characteristics, and functional properties of the raw RIDF and modified RIDF were comparatively analyzed. The results showed that all three modification methods, especially the ultrasound-cellulase combination treatment, increased the soluble dietary fiber (SDF) content of RIDF, while also causing a transition in surface morphology from smooth and dense to wrinkled and loose structures. Compared with the raw RIDF, the modified RIDF, particularly UC-RIDF, displayed significantly improved water-holding capacity (WHC), oil-binding capacity (OHC), and swelling capacity (SC), with increases of 12.0%, 84.7%, and 91.3%, respectively. Additionally, UC-RIDF demonstrated the highest nitrite ion adsorption capacity (NIAC), cholesterol adsorption capacity (CAC), and bile salt adsorption capacity (BSAC). In summary, the combination of ultrasound and cellulase treatment proved to be an efficient approach for modifying IDF from RRTP, with the potential for developing a functional food ingredient.

Lycium barbarum seed dregs (LBSDs) were used for carboxymethyl modification, resulting in three degree of substitution samples (DS). Based on the substitution degree, samples were designated as low degree of substitution insoluble dietary fiber (L-IDF), medium degree of substitution insoluble dietary fiber (M-IDF) and high degree of substitution insoluble dietary fiber (H-IDF). Physicochemical and functional properties of IDFs were examined in relation to carboxymethylation degree. Infrared Fourier transform spectroscopy (FT-IR) confirmed the carboxymethyl group. According to the results, IDF, L-IDF, M-IDF, and H-IDF acquired higher enthalpy changes, and their thermal stability improved significantly. A higher DS resulted in an increase in hydration properties such as water retention capacity and water swelling capacity, as well as functional properties such as glucose adsorption capacity, nitrite ion adsorption capacity, and cholesterol adsorption capacity. As a result, carboxymethylation could effectively enhance the biological properties of L. barbarum seed dreg insoluble dietary fiber (LBSDIDF).

In this study, we developed a process combining dilute alkali (NaOH or NaHCO3) and physical (disk milling and/or ball milling) treatments to improve the functionality and fermentability of corn fiber. The results showed that combining chemical with physical processes greatly improved the functionality and fermentability of corn fiber. Corn fiber treated with NaOH followed by disk milling (NaOH-DM-CF) had the highest water retention (19.5 g/g), water swelling (38.8 mL/g), and oil holding (15.5 g/g) capacities. Moreover, NaOH-DM-CF produced the largest amount (42.9 mM) of short-chain fatty acid (SCFA) during the 24-hr in vitro fermentation using porcine fecal inoculum. In addition, in vitro fermentation of NaOH-DM-CF led to a targeted microbial shifting to Prevotella (genus level), aligning with a higher fraction of propionic acid. The outstanding functionality and fermentability of NaOH-DM-CF were attributed to its thin and loose structure, decreased ester linkages and acetyl groups, and enriched structural carbohydrate exposure.

Okara, as a by-product of soybean processing, is rich in insoluble dietary fiber (IDF), which is a carbohydrate polymer with various insoluble polysaccharides. Nowadays, the extraction of IDF with excellent functional properties has become a research hotspot. In this work, we further proposed an alternating alkali/ultrasound method for the efficient extraction of IDF. The sequential treatments of alkali (A-ISF), alkali-ultrasonic (AU-ISF), ultrasonic-alkali (UA-ISF), ultrasonic-alkali-ultrasonic (UAU-ISF) and alkali-ultrasonic-alkali (AUA-ISF) were applied to extract insoluble soybean fiber (ISF). FTIR and XRD results proved the typical structure of ISFs, and TGA results demonstrated the improved thermal stability of UAU-ISF and AUA-ISF. Chemical composition measurement showed that UAU-ISF and AUA-ISF exhibited higher cellulose content (>83 %). SEM results revealed that ultrasonic treatment led to a decomposition of okara matrix and significant porous structure in ISFs with an amplified collapse effect, resulting in an increase of the pore size of ISFs, and strengthening the properties of UAU-ISF and AUA-ISF in higher water (>15 g/g)/oil (>12 g/g) holding capacities, cholesterol binding capacity (>36 mg/g), and cation exchange capacity (>0.3 mmol/g), thus providing new insights for the preparation of ISF with high functional properties that are beneficial for human intestinal health.