Effect of sterilisation on dietary fibre and physicochemical properties of onion by-products

Effects of food processing on in vitro glucose release of high methylester pectin-enriched doughs

The incidence of type 2 diabetes is linked to consuming processed, high-glycemic foods low in dietary fiber. Soluble dietary fibers are known to improve blood glucose tolerance. This study examined the impact of processing on the in vitro glucose release of fiber-rich, high-glycemic foods. The impact of composition and microstructure on in vitro glucose release and starch digestibility was evaluated in doughs - untreated, baked at 180 °C, and extruded at 150 °C and 180 °C - with partial enrichment of high-methylester pectin. Pectin enrichment decreased starch digestibility, altered the food matrix, and doubled in vitro chyme-viscosity resulting in reduced glucose release in baked (180 °C), and extruded (150 °C) products. Baking or extrusion cooking increased starch digestibility - converting slowly into rapidly available starch and free glucose. Additionally, resistant starch levels were enhanced by up to fivefold. The variations in glucose release originated from a complex interplay between starch digestibility, viscosity, and the food matrix.

Effects of high-pressure microfluidization treatment on the structural, physiochemical properties of insoluble dietary fiber in highland barley bran

High-pressure microfluidization treatment (HPMT) was performed on the insoluble dietary fiber (IDF) of highland barley bran (HBB), with conditions set at 60 MPa (IDF-60), 120 MPa (IDF-120), and two consecutive high-pressure treatments at 120 MPa (IDF-120-2), respectively. Then the particle size, structural, physicochemical and adsorption properties of different IDF samples were analyzed. After HPMT, the particle size of IDF samples gradiently decreased (p < 0.05), and part of IDF was transferred into soluble dietary fiber (SDF), accompanied by the decrease of hemicellulose and lignin content. In addition, the morphology of the IDF samples became more fragmented and wrinkled, and the two consecutive treatments at 120 MPa significantly damaged the crystalline structure of the IDF. Moreover, the adsorption capacities to water, oil, cholesterol, and NO2- were basically enhanced with the increase of treatment pressure and treatment number. The IDF-120-2 sample had the strongest water/oil-holding, swelling, and cholesterol trapping capacities, and the IDF-120 showed strongest NO2- trapping capacity (pH = 2). Through the correlation analysis, the adsorption capacities were positively to the particle size and SDF content, and negatively correlated with the specific surface area (SSA) and IDF content. The adsorption capacities of IDF for the four substances were positively correlated with each other.

Upcycling Rocha do Oeste Pear Pomace as a Sustainable Food Ingredient: Composition, Rheological Behavior and Microstructure Alone and Combined with Yeast Protein Extract

This work explores the potential of Rocha do Oeste pear pomace to be used as a sustainable and healthy food ingredient. Moreover, the enrichment with yeast protein extract (YPE) may be useful to design innovative food products. The main goals of this study were to assess pear pomace concerning: (i) chemical composition and antioxidant capacity; (ii) rheology, texture, and microstructure characterization (alone or enriched with YPE), before and after heating. The results showed that pear pomace was a rich source of dietary fibers (74.5% DW), with phenolic compounds (3.9 mg chlorogenic acid equivalents/g dry weight), also presenting antiradical activity (3.90 μmol Trolox equivalents/g DW). Pear pomace showed a shear thinning behavior and a typical soft-gel behavior, which was not affected by YPE enrichment, thus suggesting that YPE did not affect pear pomace technological properties. Thermal treatment also did not alter pear pomace rheological properties. YPE addition induced a decrease in the apparent viscosity and a destabilizing effect, compared to the samples that were subjected to thermal processing. These results highlight the importance of pear pomace and the use of YPE for protein enrichment, opening new opportunities for their exploitation.

Modification of Dietary Fibers to Valorize the By-Products of Cereal, Fruit and Vegetable Industry-A Review on Treatment Methods

Many by-products originating from cereal, fruit and vegetable industries contain quite high amounts of dietary fiber (DF), which play an important role in maintaining the healthy state of the human body. Nevertheless, huge proportions of these by-products are still underutilized as feed ingredients, to generate energy within an anaerobic digestion plant or even landfilled. One of the biggest hindrances in the valorization of such by-products is their very low soluble dietary fiber (SDF) to insoluble dietary fiber (IDF) ratios, impairing their nutritional functionality, palatability and technological applicability. Therefore, it is of interest to develop methods that can enhance the SDF to IDF ratio and that can be applied to the by-product streams of the food industry, enabling better valorization perspectives for human nutrition purposes. In this regard, the review paper provides an overview of existing technologies to modify the SDF to IDF ratio in by-products of the food industry by means of physical, chemical and biological treatments. For each type of treatment, available data on application examples including achieved increases in SDF contents are given. Additionally, a comparative discussion regarding the advantages and disadvantages of these methods is provided.

Dietary Fiber in Plant Cell Walls—The Healthy Carbohydrates

Dietary fiber (DF) is one of the major classes of nutrients for humans. It is widely distributed in the edible parts of natural plants, with the cell wall being the main DF-containing structure. The DF content varies significantly in different plant species and organs, and the processing procedure can have a dramatic effect on the DF composition of plant-based foods. Given the considerable nutritional value of DF, a deeper understanding of DF in food plants, including its composition and biosynthesis, is fundamental to the establishment of a daily intake reference of DF and is also critical to molecular breeding programs for modifying DF content. In the past decades, plant cell wall biology has seen dramatic progress, and such knowledge is of great potential to be translated into DF-related food science research and may provide future research directions for improving the health benefits of food crops. In this review, to spark interdisciplinary discussions between food science researchers and plant cell wall biologists, we focus on a specific category of DF—cell wall carbohydrates. We first summarize the content and composition of carbohydrate DF in various plant-based foods, and then discuss the structure and biosynthesis mechanism of each carbohydrate DF category, in particular the respective biosynthetic enzymes. Health impacts of DF are highlighted, and finally, future directions of DF research are also briefly outlined.

Physicochemical, functional, and microstructural properties of modified insoluble dietary fiber extracted from rose pomace

Rose pomace, a by-product of the essential oil extraction process, is rich in dietary fiber. Insoluble dietary fiber (IDF) extracted from rose pomace was modified by enzymatic hydrolysis (EH) and ultrasound-assisted enzymatic hydrolysis (UEH) methods, and their physicochemical, functional, and microstructural properties were studied. The results showed that EH treatment performed better in the yield of soluble dietary fiber and the glucose adsorption capacity than UEH which contributed to better oil-holding, swelling, cation-exchange, and cholesterol adsorption capacities. Moreover, cellulose, hemicellulose, and lignin were detected based on Fourier transform infrared spectra and X-ray diffraction patterns. Scanning electron microscopy revealed that IDF had a shaly surface with a loose block structure after modification. In conclusion, different modification degrees have respective advantages, and modified IDF from rose pomace could be utilized in the food industry as a new source of functional ingredients, as well as to increase the economic value of rose products.

Structural, antioxidant and adsorption properties of dietary fiber from foxtail millet (Setaria italica) bran

BACKGROUND

Foxtail millet (Setaria italica) bran is a by-product of millet processing, rich in dietary fiber (DF) and has great application value. A comparative study was conducted to explore the differences in structural and functional properties among millet bran DF, soluble dietary fiber (SDF) and insoluble dietary fiber (IDF).

RESULTS

There was a significant difference in the content of monosaccharides between SDF and IDF, in which xylose, arabinose and glucose were the main compositions. The results of scanning electron microscopy showed that DF and IDF had different forms of network structure, and SDF presented a sign of mutual adhesion. The total phenolic and flavonoid contents were 0.54 and 0.08 g kg^-1 in SDF. Antioxidant activity of SDF was higher than that of IDF based on the evaluation of free radical scavenging and iron reducing capacity in vitro. Meanwhile, the glucose dialysis retardation index of IDF and SDF was 12.59% and 9.26% at 30 min, respectively. And, there was no significant difference in the adsorption capacity of glucose among different samples (P > 0.05). Furthermore, SDF had strong α-amylase inhibition (17.92% inhibition rate) and sodium cholate adsorption capacities; the adsorption amount was 16.76 g kg^-1 in 2.00 g L^-1 sodium cholate solution.

CONCLUSION

Foxtail millet bran DF, especially SDF, has good functional properties and would be a suitable ingredient for health-beneficial food production. However, the relevant verification trials in vivo need to be carried out in the next steps. © 2019 Society of Chemical Industry.

Physicochemical Properties and Intestinal Health Promoting Water-Insoluble Fiber Enriched Fraction Prepared from Blanched Vegetable Soybean Pod Hulls

Different methods can be used to change the fiber compositions of food, and they consequently affect the physicochemical properties and physiological activities. The present study compared the effects of a blanching treatment on the physicochemical properties of water-insoluble fiber enriched fraction (WIFF) from three varieties of vegetable soybean pod hulls (tea vegetable soybean pod hull, TVSPH; black vegetable soybean pod hull, BVSPH; 305 vegetable soybean pod hulls, 305VSPH) and evaluated their effects on intestinal health in hamsters. Blanching may increase the soluble dietary fiber (SDF) content of WIFF in the 305VSPH variety by solubilizing cell wall components and releasing water-soluble sugars. Thus, the WIFF in the 305VSPH variety after blanching may be composed of cellulose and pectic substances. The WIFF of the blanched 305VSPH (B-305VSPH) variety exhibited the highest physicochemical properties, such as a water-retention capacity (11.7 g/g), oil-holding capacity (9.34 g/g), swelling property (10.8 mL/g), solubility (12.2%), and cation-exchange capacity (221 meq/kg), of the three varieties examined. The supplementation of B-305VSPH WIFF in the diet resulted in significantly (p < 0.05) lower cecal and fecal ammonia; activities of fecal β-d-glucosidase, β-d-glucuronidase, mucinase, and urease; as well as higher cecal total short-chain fatty acids relative to other diets. In addition, microbial analysis suggested that fecal bifidobacteria growth was enhanced by the consumption of B-305VSPH WIFF. Therefore, B-305VSPH WIFF may be applicable as a potential functional ingredient in the food industry for the improvement of intestinal health.

Onion (Allium cepa L.) is potentially a good source of important antioxidants

Six different cultivars of onions available in the Kuwaiti market were analyzed for various physic-chemical properties, such as, moisture content, sugar composition, TBARS as malondialdehyde, total phenolic content, as well as trolox equivalent antioxidant capacity, these cultivars comprised of US onions white, US onions yellow, Indian onions red, Egyptian onions red, New Zealand onions golden and Saudi onions white. Layers from each onion bulb were manually cut and separated into three nearly equal portions, i.e., outer layers, middle layers and the inner layers. The outermost layers of the bulb showed the highest concentration of antioxidant compounds and a distinct decreasing trend was observed towards the innermost layers in all types of onion samples. The onion samples studied showed variations in carbohydrate contents (glucose, fructose and sucrose), which would have important implications in affecting the flavor (sweetness and pungency) and the suitability of these onions for processing. An important observation is about the distribution of antioxidant compounds with the highest contents in the outmost layers of the onions than in their middle and inner layers. Unfortunately, these outer layers are generally discarded by the consumers thus depriving them of the important health-promoting phytochemicals.

Changes of Complex Carbohydrates of White Jack Bean (Canavalia Ensiformis) During Autoclaving-Cooling Cycles

The extraction of white jack bean (Canavalia ensiformis) protein isolate frequently leaves a lot of precipitates containing complex carbohydrates such as starch, dietary fiber, and resistant starch. Repeated autoclaving – cooling cycles can increase the content of soluble fiber and resistant starch. The aim of this study was to determine changes of dietary fiber and resistant starch content of complex carbohydrates of white jack bean during autoclaving-cooling cycles and characterization of its chemical composition and functional properties. The experiment was conducted by applying the autoclaving process at 121oC for 15 minutes followed by cooling at 4oC for 24 hours up to 5 times. Sample was taken from each cycle of autoclaving – cooling. The best treatment was the sample with the highest total soluble fiber and resistant starch content. The best sample will be determined its chemical composition and functional properties. This study used a one-way analysis of variance to subject the data according to Completely Randomized Design. Duncan’s Multiple Range Test was applied to determine significant differences among 5 treatment means at the 5% significance level. The highest value of total soluble fiber and resistant starch content was obtained from autoclaving-cooling cycles of 3 times. The treatment increased the soluble fiber and resistant starch by 14.37% and 18.34%, respectively, but decreased 14.41% insoluble fiber. The complex carbohydrates of white jack bean treated with autoclaving-cooling cycles of 3 times had chemical composition: 10.68% moisture content, 0.92% ash content, 0.02% fat content, 1.85% protein content, 97.20% carbohydrate content (by difference), 68.42% starch content, and 14.90 ppm HCN. It also had functional properties: 351.67% WHC, 115.67% OHC, 775.33% SC, 84.63 meq/kg CEC. The conclusion was the white jack bean carbohydrate complex treated with 3 times autoclaving-cooling cycles was the best treatment to produce the highest value of total soluble fiber and resistant starch content. We suggest to examine another autoclaving temperature and cooling time to compare the result.

The dietary fiber profile of fruit peels and functionality modifications induced by high hydrostatic pressure treatments

The effect of high hydrostatic pressure (HHP) and temperature on composition of non-conventional dietary fiber (DF) sources and functional properties were evaluated. Mango, orange, or prickly pear peels were processed at 600 MPa during 10 min at 22 ℃ and 55 ℃. Total (TDF), soluble (SDF), and insoluble (IDF) dietary fiber, water/oil holding, and retention capacity, solubility, swelling capacity, and bulk density were assayed. An increment in the SDF content was observed due to the effect of pressure with the greatest changes noticed in mango peel, increasing from 37.4% (control) to 45.7% (SDF/TDF) in the HHP-treated (55 ℃) sample. Constant values of TDF after the treatments suggest a conversion of IDF to SDF in mango (38.9%–40.5% dw) and orange (49.0%–50.8% dw) peels. The highest fiber solubility values were observed for mango peel ranging between 80.3% and 83.9%, but the highest increase, from 55.1% to 62.3%, due to treatment was displayed in orange peel processed at 22 ℃. A relationship between DF modifications induced by HHP treatment and changes in the functional properties of the materials was established. Application of HHP opens up the opportunity to modify non-conventional sources of DF and to obtain novel functional properties for different food applications.

Physicochemical and functional properties of micronized jincheng orange by-products (Citrus sinensis Osbeck) dietary fiber and its application as a fat replacer in yogurt

Orange by-products from juice extraction are generally discarded or used in animal feed due to their low market value. However, orange by-products show potential as dietary fiber (DF) and fat replacers in products such as yogurt. This study assessed the benefits of using orange by-products in DF-enriched materials such as DF powders (OP) and micronized DF with ball-milling (MDF). The study also investigated the effects of adding different levels of OP and MDF on the quality of low-fat yogurt. Results show that MDF showed better physicochemical and functional properties than OP, and that 2% MDF as a fat replacer in yogurt retained most of the textural and sensory properties of full-fat yogurt. Therefore, this study showed that MDF is a promising alternative as a fat replacer in low-fat yogurt, without sacrificing good taste and other qualities of full-fat yogurt.

Sequential extraction of polysaccharides from enzymatically hydrolyzed okara byproduct: physicochemical properties and in vitro fermentability

Okara, a byproduct of soymilk production, has been upgraded through the use of an enzymatic treatment with Ultraflo L® to give a product (okara(ET)) which has a higher content of soluble dietary fibre and an enhanced ratio of soluble: insoluble fibre than is found in okara without treatment. Polysaccharides were isolated from okara(ET) by sequential extraction to yield soluble fractions in water (22%), CDTA (8.7%), alkali (37.7%) without and NaClO2 (9.1%) and the cellulosic residue represents a (22.5%). The physicochemical properties of okara(ET) were improved due to the enzymatic treatment: oil retention capacity (6.94g/g), water retention capacity (10.76g/g) and swelling capacity (13.85g/g) were higher than in okara that had not undergone enzymatic treatment. The gelation capacity (8%) and the cation exchange capacity (8.96mEq/kg) of okara(ET) were lower than that of other byproducts. Short chain fatty acid production during in vitro fermentation of okara(ET) by a pure culture of Bifidobacterium bifidus was mainly represented by acetic acid, followed by propionic and butyric acids. In addition, the decreases in pH and substrate consumption demonstrated the bifidogenic capacity of okara(ET).