Effect of extraction methods on structural, physiochemical and functional properties of dietary fiber from defatted walnut flour

Extraction and Characterization of Antioxidants and Cellulose from Green Walnut Husks

The ultrasound-assisted extraction process with microwave pretreatment was modeled and optimized to maximize the yield of antioxidants from green walnut husks using a response surface methodology with Box-Behnken design. In this design, the ultrasound-assisted extraction time (10-40 min), ultrasound-assisted extraction temperature (40-60 °C), and microwave pretreatment time (20-60 s) were selected as the factors, while the total antioxidant content was defined as the response. The solvent of choice for extracting antioxidants was 50% (v/v) ethanol. After optimization using the desirability function, an ultrasound-assisted extraction time of 23 min, ultrasound-assisted extraction temperature of 60 °C, and microwave pretreatment time of 60 s were proposed as the optimal conditions and their validity was verified. Under these conditions, the experimentally determined total antioxidant content was 3.69 g of gallic acid equivalent per 100 g of dry matter. In addition to phenolics, UHPLC-ESI-MS/MS analysis indicated the presence of lipids, quinones, terpenoids, and organic acids in the extract. After the antioxidant extraction, the solid residue was further processed to isolate cellulose in line with the concept of sustainable manufacturing. The structural characterization and hydration properties of cellulose were analyzed to identify its key features and assess its potential for value-added applications. The results demonstrate that green walnut husks are a valuable and cost-effective agro-industrial byproduct for extracting antioxidants and isolating cellulose. This aligns with the principles of a circular economy and the sustainable production of natural compounds.

Water-insoluble dietary fiber from walnut relieves constipation through Limosilactobacillus reuteri-mediated serotonergic synapse and neuroactive ligand-receptor pathways

Dietary fiber can alleviate functional constipation (FC) by modulating the gut microbiota. To clarify the prebiotic properties of walnut insoluble dietary fiber (WIDF), we explored its structural characteristics and laxative mechanism. A galacturonic acid and glucose-rich WIDF was isolated from walnuts by using a complex enzymatic method. Animal experiments results showed that WIDF could effectively alleviate the symptoms of loperamide-induced FC in mice, including shortening the defecation time, increasing the wet weight and water content of feces, and promoting intestinal motility. WIDF might alleviate FC through activating serotonergic synapse and inhibiting the delta-opioid receptor/inducible nitric oxide synthase (Oprd/iNOS) pathways. Importantly, WIDF treatment altered the structure and composition of the gut microbiota. Correlation analysis revealed that Bacillus and its dominant ASV17, which is considered to be the key microbe for constipation alleviation, were strongly associated with constipation phenotypes. Based on pure culture and 16S rRNA gene phylogenetic analysis, Limosilactobacillus reuteri (L. reuteri), which is 100 % similar to ASV17, was isolated and identified from the feces of WIDF-treated mice. L. reuteri relieved FC by modulating serotonergic synapse and the Oprd/iNOS pathways. These results suggested that WIDF and L. reuteri treatment is a prospective strategy for the prevention of constipation.

Modification, biological activity, applications, and future trends of citrus fiber as a functional component: A comprehensive review

Citrus fiber, a by-product of citrus processing that has significant nutritional and bioactive properties, has gained attention as a promising raw material with extensive developmental potential in the food, pharmaceutical, and feed industries. However, the lack of in-depth understanding regarding citrus fiber, including its structure, modification, mechanism of action, and potential applications is holding back its development and utilization in functional foods and drugs. This review explores the status of extraction methods and modifications applied to citrus fiber to augment its health benefits. With the aim of introducing readers to the potential health benefits of citrus fibers, we have placed special emphasis on their regulatory mechanisms in the context of various conditions, including type 2 diabetes mellitus, cardiovascular disease, obesity, and cancer. Furthermore, this review highlights the applications and prospects of citrus fiber, aiming to provide a theoretical basis for the utilization and exploration of this valuable resource.

Walnut Flour as an Ingredient for Producing Low-Carbohydrate Bread: Physicochemical, Sensory, and Spectroscopic Characteristics

Walnut flour (WF) is a nutrient-rich source that can be used as an alternative for individuals on a gluten-free diet. This study aimed to assess the physical, chemical, and sensory changes in low-carbohydrate bread when supplemented with WF. Molecular-level changes were also examined using ATR-FTIR spectra. The bread recipe, containing buckwheat and flaxseed, was enriched with WF at levels ranging from 5% to 20%. The addition of WF resulted in increased loaf volume and decreased baking loss. Enriched bread samples showed higher protein content, while fat and available carbohydrate content decreased. Additionally, WF incorporation led to a decrease in crumb brightness and an increase in redness (from 23.1 to 25.4) and yellowness (from 23.8 to 26.7). WF also increased crumb hardness and chewiness. Moreover, the tested additives primarily influenced the intensity of FTIR spectra, indicating changes in protein, carbohydrate, and fat content, with increased band intensity observed in the protein region. We particularly recommend bread with a WF content of 15%. This type of bread is characterized by high consumer acceptance. Furthermore, compared to bread without the addition of WF, it has a higher content of phenolic compounds, protein, and fat by approximately 40%, 8%, and 4%, respectively. The antioxidant activity of this bread, determined using the ABTS and DPPH methods, is also significantly higher compared to the control bread.

Valorization of Soybean Residue (Okara) by Supercritical Carbon Dioxide Extraction: Compositional, Physicochemical, and Functional Properties of Oil and Defatted Powder

In the context of food waste valorization, the purpose of this study is to demonstrate the complete valorization of soybean residue (okara) through supercritical carbon dioxide extraction (SCE). Okara oil (OKO) was separated from full-fat powder (FFP) using SCE with and without ethanol (EtOH) as a cosolvent. The kinetics of extraction, chemical composition, and physicochemical, functional, and health-promoting properties of OKO and defatted powder (DFP) were determined. The process yielded 18.5% oil after 450 min. The soluble dietary fiber and protein of the DFP increased significantly; its water and oil absorption capacities increased despite the decrease in swelling capacity corresponding to particle size reduction. The OKO was rich in linoleic and oleic acids, with a ratio of ω6-to-ω3 fatty acids = 9.53, and EtOH increased its phenolic content (0.45 mg GAE/g), aglycone content (239.6 μg/g), and antioxidant capacity (0.195 mg TE/g). The DFP paste showed gel-like consistency and shear-thinning flow behavior, whereas the OKO showed characteristic transition of the product and affected lubrication at contact zones. Both fractions showed potential as food ingredients based on their nutritional and functional properties, as well as the capability of modifying the microstructure of a model food system.

Effects of shear emulsifying/ball milling/autoclave modification on structure, physicochemical properties, phenolic compounds, and antioxidant capacity of lotus (Nelumbo) leaves dietary fiber

Lotus (Nelumbo) leaves are rich in polyphenols and dietary fiber, which have the potential as a high-quality fiber material in functional food. However, lotus leaves exhibit dense structure and poor taste, it is vital to develop appropriate modification methods to improve the properties of lotus leaves dietary fiber. In this study, the effects of three modification methods with shear emulsifying (SE), ball milling (BM), and autoclave treatment (AT) on structure, physicochemical properties, phenolic compounds, and antioxidant capacity of lotus leave dietary fiber (LDF) were evaluated. SEM indicated that there were significant differences in the microstructure of modified LDFs. FT-IR spectra and X-ray diffraction pattern of modified LDFs revealed similar shapes, while the peak intensity and crystalline region changed by modification. SE showed the greatest effect on crystallization index. SE-LDF had the highest water holding capacity, water swelling capacity, and bound phenolic content in LDFs, which increased by 15.69, 12.02, and 31.81%, respectively, compared with the unmodified LDF. BM exhibited the most dramatic effect on particle size. BM-LDF had the highest free phenolic and total phenolic contents in LDFs, which increased by 32.20 and 29.05% respectively, compared with the unmodified LDF. Phenolic compounds in LDFs were mainly free phenolic, and modifications altered the concents of flavonoids. The BM-LDF and SE-LDF exhibited higher antioxidant capacity than that of AT-LDF. Overall, SE-LDF showed better physical properties, and BM-LDF showed better bioactive components. SE and BM were considered to be appropriate modification methods to enhance the properties of LDF with their own advantages.

Comparison of physicochemical and in vitro hypoglycemic activity of bamboo shoot dietary fibers from different regions of Yunnan

In this study, the physicochemical properties, thermal characteristics, and in vitro hypoglycemic activity of dietary fibers extracted from four bamboo shoots were characterized and compared. The results showed that Dendrocalamus brandisii Munro (C-BSDF) had the highest dietary fiber content (6.1%) and the smallest particle size (222.21 μm). SEM observations found that C-BSDF exhibited a loose and porous microstructure, while FTIR and XRD confirmed that C-BSDF had a higher degree of decomposition of insoluble dietary fiber components and the highest crystallinity, resulting in a better microstructure. Furthermore, C-BSDF exhibited excellent physiochemical properties with the highest water hold capacity, water swelling capacity, and preferable oil holding capacity. Thermal analysis showed that C-BSDF had the lowest mass loss (64.25%) and the highest denaturation temperature (114.03°C). The hypoglycemic activity of dietary fibers from bamboo shoots were examined in vitro and followed this order of activity: C-BSDF>D-BSDF>A-BSDF>B-BSDF. The inhibition ratios of GAC, GDRI and α-amylase activity of C-BSDF were 21.57 mmol/g, 24.1, and 23.34%, respectively. In short, C-BSDF display excellent physicochemical and functional properties due to its high soluble dietary fiber content, small particle size with a high specific surface area, and loose microstructure. Thus, D. brandisii Munro can be considered a promising new source of dietary fiber for hypoglycemic health products.

Comparison of different extraction methods on the physicochemical, structural properties, and in vitro hypoglycemic activity of bamboo shoot dietary fibers

The effect of alkali extraction (AE), enzymatic extraction (EE), ultrasonic-assisted enzymatic extraction (UAEE), and shear homogeneous-assisted enzymatic extraction (SHAEE) on the physicochemical, structural properties, and in vitro hypoglycemic activity of bamboo shoot dietary fibers (BSDF) were investigated and compared. BSDF obtained by AE had the lowest protein content and crystallinity index. The lowest oil holding capacity (OHC) and highest protein content were observed in EE. BSDF generated highest OHC and glucose adsorption capacity by UAEE. SHAEE obtained the highest SDF content (17.89%), water-holding capacity (8.81 g/g), and α-amylase activity inhibition ratio (19.89%) and the smallest particle size (351.33 μm). BSDF extracted by SHAEE and UAEE presented a porous and loose structure. Furthermore, the in vitro hypoglycemic activity of the four BSDF samples generally followed the order of SHAEE > UAEE > EE > AE. Results show that SHAEE is an innovative and promising method to obtain BSDF with its excellent physicochemical and functional properties.

Ultrasound-Assisted Modification of Insoluble Dietary Fiber from Chia (Salvia hispanica L.) Seeds

Modification of insoluble dietary fiber (IDF) to soluble dietary fiber (SDF) improves not only the various health benefits but also the functional properties for improved product development. This research aimed to examine the effects of sonication treatment on the functional and physicochemical properties with possible structural changes in chia seeds dietary fiber. Central composite design was applied to optimize the sonication treatment process (amplitude 55%, time 20 min, and temperature 40°C) based on the oil holding capacity (OHC) and water holding capacity (WHC) as responses. Under these optimum conditions, ultrasound-treated IDF exhibited better functional and physicochemical properties such as OHC, WHC, glucose adsorption capacity (GAC), and water retention capacity (WRC) than untreated IDF. Fourier-transform infrared spectroscopy further confirmed the structural changes in treated and untreated IDF to explain the changes in the studied parameters.

Evaluation of the Structural, Physicochemical and Functional Properties of Dietary Fiber Extracted from Newhall Navel Orange By-Products

Ultrasound-assisted enzymatic treatment was used to treat Newhall navel orange peel and residue, and then the structural, physicochemical and functional properties of extracted soluble dietary fibers (SDF) and insoluble dietary fibers (IDF) were investigated. The structural properties were determined using scanning electron microscopy, X-ray diffraction, FT-IR and monosaccharide composition. Among these dietary fibers, residue-SDF showed a more complex structure, while peel-IDF exhibited a looser structure. Four samples showed representative infrared spectral features of polysaccharides, typical cellulose crystalline structure and diverse monosaccharide composition. Furthermore, residue-IDF exhibited higher oil-holding capacity (2.08 g/g), water-holding capacity (13.43 g/g) and nitrite ion adsorption capacity (NIAC) than other three samples, and residue-SDF showed the highest swelling capacity (23.33 mL/g), cation exchange capacity (0.89 mmol/g) and cholesterol adsorption capacity (CAC) among these dietary fibers. In summary, this study suggests that the residue-SDF and residue-IDF could be used as the ideal dietary fibers for application in the functional food industry.

Extraction, modification, and property characterization of dietary fiber from Agrocybe cylindracea

Dietary fiber (DF) has gained a great attention owing to its potential health benefits. Agrocybe cylindracea is an edible fungus with high protein and low fat contents, which is also an enriched source of DF. However, limited study has been conducted on optimizing the conditions of A. cylindracea-derived DF extraction and modification as well as characterizing its properties. In this study, ultrasound-assisted enzymatic method for DF extraction was optimized as the following conditions: liquid material ratio of 29 ml/g, α-amylase concentration of 1.50%, protamex concentration of 1.20%, and ultrasonic power of 150 W, which improved the DF extraction yield to 37.70%. Moreover, high temperature modification (HTM) and cellulase modification (CEM) were applied to modify A. cylindracea-derived DF. The results showed that HTM had more potential capacity in converting insoluble DF into soluble DF, and DF with HTM exhibited more advantages in its physicochemical properties than DF with CEM. The DF with both HTM and CEM showed antioxidant activities, reflected by the increased reducing power as well as DPPH radical, hydroxyl radical, and ABTS+ scavenging capabilities in vitro. These findings could offer a reference for the extraction, modification, and characterizing various properties of DF from A. cylindracea, which would establish the foundation for the comprehensive application of fungi-derived DF.

Effect of thermal stabilization on physico-chemical parameters and functional properties of wheat bran

The food industry also focuses on the use of by-products from food processing. Wheat bran is a valuable by-product of the wheat milling process, which is rich in dietary fiber. In addition to nutritional value, dietary fiber has a functional potential in the production of novel foods. Pre-treatment of the dietary fiber using different methods can change its functional properties. The objective of this study was to evaluate the effect of stabilization process on physico-chemical parameters and functional properties of wheat bran. Wheat bran from two wheat variety was treated using microwave and hot air heating. It was observed that wheat bran included more than 45% of total dietary fiber. Results suggested that treatment of bran using both method increased total dietary fiber content. Thermal treatment process decreased the anti-nutritional agent in bran samples. Phytic acid content diminishing of 44% and 49% was observed in microwave treated bran samples. Moreover, treatment of bran using a hot air heating improved the hydration properties (water holding, water retention and swelling capacity), while oil holding capacity was not significantly altered. Treatment decreased the antioxidant activity of treated bran samples. It was observed that thermal treatment modified the color parameters of bran (lightness, yellowness and hue angle decreased and redness and Chroma increased).