Soluble Fiber Fractions Research Articles

Molecular Structure and Properties of Resistant Dextrins from Potato Starch Prepared by Microwave Heating.

The dextrinization of potato starch was performed using a sophisticated single-mode microwave reactor with temperature and pressure control using 10 cycles of heating with stirring between cycles. Microwave power from 150 to 250 W, a cycle time from 15 to 25 s, and two types of vessels with different internal diameters (12 and 24 mm) and therefore different thicknesses of the heated starch layer were used in order to estimate the impact of vessel size used for microwave dextrinization. The characteristics of resistant dextrins (RD) including solubility in water, total dietary fiber (TDF) content, color parameters, the share of various glycosidic bonds, and pasting and rheological properties were carried out. The applied conditions allowed us to obtain RDs with water solubility up to 74% at 20 °C, as well as TDF content up to 47%, with a predominance of low-molecular-weight soluble fiber fraction, with increased content of non-starch glycosidic bonds, negligible viscosity, and a slightly beige color. The geometry of the reaction vessel influenced the properties of dextrins obtained under the same heating power, time, and repetition amounts. Among the conditions used, the most favorable conditions were heating 10 times for 20 s at 200 W in a 10 mL vessel and the least favorable were 15 s cycles.

Physical and Functional Properties of Powders Obtained during Spray Drying of Cyani flos Extracts.

Edible flowers are a potential source of bioactive ingredients and are also an area of scientific research. Particularly noteworthy are Cyani flos, which have a wide range of uses in herbal medicine. The below study aimed to investigate the influence of selected soluble fiber fractions on the selected properties of physical and biochemical powders obtained during spray drying a water extract of Cyani flos. The drying efficiency for the obtained powders was over 60%. The obtained powders were characterized by low moisture content (≤4.99%) and water activity (≤0.22). The increase in the addition of pectin by the amount of 2-8% in the wall material resulted in a decrease in hygroscopicity, water solubility, and protection of flavonoids and anthocyanins both before and after digestion in the tested powders in comparison to the sample with only inulin as a carrier. Additionally, it was noted that all samples were characterized by high bioaccessibility when determining antioxidant properties and xanthine oxidase inhibition.

Effect of dietary supplementation of two fiber sources differing on fermentability and hydration capacity on performance, nutrient digestibility and cecal fermentation in broilers from 1 to 42 d of age

A total of 378 Cobb-500 male broilers were used to evaluate the effects of 2 fiber sources, differing in hydration capacity and fermentability, on gastrointestinal tract development, apparent ileal digestibility and performance from 1 to 42d of age. There were 9 replicates per each of the 3 dietary treatments, all in mash form: a wheat-soybean control (CON) diet, CON diet diluted with 1.5% of wood lignocellulose (LC diet) as a non-fermentable insoluble fiber with high hydration capacity; and CON diluted with 1.5% of a mixture of fibers (ISFC diet) containing both lignified insoluble fiber and a prebiotic soluble fiber fraction from fructooligosaccharides. Additionally, the fermentability of both fiber sources (LC and ISFC) was determined by in vitro using cecal inoculum from broilers fed the experimental diets. Both LC and ISFC treatments impaired by 4% feed conversion ratio only during the first 7d (P = 0.003) compared with CON group. In the grower period (21-42d), the ISFC group showed the best growth (P = 0.039), and at 42d tended to show the highest body weight (P = 0.095). This agrees well with the highest ileal dry matter (P = 0.033) and organic matter (P = 0.043) digestibility observed in ISFC group and the similar trend observed for ileal protein digestibility (P = 0.099) at 42d. Also, at 42 d, absolute and relative (% body weight) digestive tract weights (P ≤ 0.041) and empty gizzard weights (P ≤ 0.034) were greater for LC and ISFC groups compared to CON. The cecal molar proportion of valeratewas greatest in ISFC group (P = 0.039). In vitro gas production was higher for ISFC than for LC substrate when using either a diet-adapted or non-adapted cecal inoculum (P < 0.05). These results show the interest in combining IF with prebiotic highly fermentable fiber, such as fructooligosaccharides, in broilers to improve nutrient digestibility and finishing performance.

Supplementation with soluble or insoluble rice-bran fibers increases short-chain fatty acid producing bacteria in the gut microbiota in vitro.

Studies have shown that a diet high in fiber and prebiotics has a positive impact on human health due largely to the fermentation of these compounds by the gut microbiota. One underutilized source of fiber may be rice bran, a waste product of rice processing that is used most frequently as an additive to livestock feed but may be a good source of fibers and other phenolic compounds as a human diet supplement. Previous studies focused on specific compounds extracted from rice bran showed that soluble fibers extracted from rice bran can improve glucose response and reduce weight gain in mouse models. However, less is known about changes in the human gut microbiota in response to regular rice bran consumption. In this study, we used a Simulator of the Human Intestinal Microbial Ecology (SHIME®) to cultivate the human gut microbiota of 3 different donors in conditions containing either soluble or insoluble fiber fractions from rice bran. Using 16S rRNA amplicon sequencing and targeted metabolomics via Gas Chromatography-Mass Spectrometry, we explored how gut microbial communities developed provided different supplemental fiber sources. We found that insoluble and soluble fiber fractions increased short-chain fatty acid production, indicating that both fractions were fermented. However, there were differences in response between donors, for example the gut microbiota from donor 1 increased acetic acid production with both fiber types compared with control; whereas for donors 2 and 3, butanoic acid production increased with ISF and SF supplementation. Both soluble and insoluble rice bran fractions increased the abundance of Bifidobacterium and Lachnospiraceae taxa. Overall, analysis of the effect of soluble and insoluble rice bran fractions on the human in vitro gut microbiota and the metabolites produced revealed individually variant responses to these prebiotics.

Influence of Dietary Fibre and Protein Fractions on the Trace Element Bioaccessibility of Turnip Tops (Brassica rapa) Growing under Mediterranean Conditions

The objective of this work was to study the influence of three dietary fibre fractions (pectin, gum arabic and cellulose) and three protein fractions (casein, lactalbumin and soy) on the trace element bioaccessibility (Fe, Mn, Ni, Se and Zn) of turnip tops (B. rapa subsp. Rapa) growing under Mediterranean conditions. Then, it aimed to promote the use of this vegetable not only for direct fresh consumption but also as a main ingredient in the development of food mixtures. The results showed that soluble fibre fractions, such as pectin and gum arabic, can enhance the bioaccessibility of trace elements, such as Fe, Mn, Se and Zn. This effect was not proved for cellulose (an insoluble fibre fraction), in which, at best, no bioaccessibility effect was observed. Regarding the protein fractions, with the exception of Se, caseins and lactalbumin had a neutral effect on improving the trace element bioaccessibility. This did not hold true for soy protein, in which a considerable improvement in the bioaccessibility of Fe, Mn, Se and Zn was determined.

Ultrasound and Steam Explosion Treatments on the Quantity and Molecular Size of Soluble Fibre Obtained from Un-purified and Purified Rice Bran

Rice bran (RB) is a major by-product of the rice industry, and the high proportion (~90%) of insoluble fibre (IF) is the main reason limiting its applications in foods. Thus, the objective of this research is to enhance the solubility of rice bran fibre and decrease the molecular weight (MW) of the soluble fibre (SF) fraction through ultrasound (US) and steam explosion (SE) treatments. The main sugars in the RB fibre were xylose and arabinose, with glucose, galactose, and mannose present in the side chains. The ratio of Ara/Xyl was 0.92 for the un-purified and 1.02 for the purified RB, reflecting the high degree of substitution of the xylan backbone. The highest amount of SF was obtained from RB treated at 60% US amplitude, 20 min treatment, where 7.8% (un-purified) and 35.2% (purified), respectively. For SE treatments, the amount of SF in un-purified RB increased as the pressure increased from 0.3 and 0.6 MPa, which were 6.10±0.34 and 8.83±0.56%, respectively. Meanwhile, the highest SF fraction (35.2%) of purified RB was obtained from the SE treatment at 0.6 MPa. The SF produced from both treatments mainly contained oligosaccharides with MW &lt;1 kDa, with those produced by the SE treatment generally smaller than those by the US treatment. Purification of RB significantly enhanced the efficiency of the US and SE treatments in breaking down the IF into the SF.

Fractionation and physicochemical characterization of dietary fiber of kenaf (Hibiscus cannabinus L.) seed.

Kenaf seeds are underutilized kenaf plant by-products, containing essential nutrients including dietary fiber (DF), which can be potentially utilized as food ingredients. The present study aimed to evaluate the physicochemical characteristics of kenaf seed fiber fractions extracted from kenaf seed. Defatted kenaf seed powder yielded four DF fractions: alkali-soluble hemicellulose (146.4 g kg-1 ), calcium-bound pectin (10.3 g kg-1 ) and acid-soluble pectin (25.4 g kg-1 ) made up the soluble fibre fraction, whereas cellulose (202.2 g kg-1 ) comprised the insoluble fraction. All fractions were evaluated for their physicochemical properties. The DF fractions contained glucose, mannose, xylose and arabinose, and a small amount of uronic acid (1.2-2.7 g kg-1 ). The isolated pectin fractions had a low degree of esterification (14-30%). All the isolated DF fractions had high average molecular weights ranging from 0.3 to 4.3 × 106 g mol-1 . X-ray diffractogram analysis revealed that the fractions consisted mainly of an amorphous structure with a relative crystallinity ranging from 31.6% to 44.1%. The Fourier-transform infrared spectroscopy spectrum of kenaf seed and its DF fractions showed typical absorption of polysaccharides, with the presence of hydroxyl, carboxyl, acetyl and methyl groups. Scanning electron microscopy analysis demonstrated that the raw material with the rigid structure resulted in soluble and insoluble DF fractions with more fragile and fibrous appearances, respectively. The soluble DF demonstrated greater flowability and compressibility than the insoluble fractions. These findings provide novel information on the DF fractions of kenaf seeds, which could be used as a potential new DF for the food industry. © 2023 Society of Chemical Industry.

Effects of Barley- and Oat-Based Diets on Some Gut Parameters and Microbiota Composition of the Small Intestine and Ceca of Broiler Chicken

Barley and oats can be alternatives of corn and wheat in poultry nutrition and used at higher inclusion rates. Both cereals contain hulls, a structural fiber source, that can be beneficial for the gizzard function of birds. They also contain high amounts of β-glucans, of which about 60–70% is water soluble. Soluble β-glucans increase gut viscosity, impair digestion, and modify gut microbiota. The aim of this trial was to evaluate the effects of feeding oats and barley at high inclusion rates and with exogenous glucanase on some relevant gut parameters and the microbiota composition of jejunum content (JC), jejunum mucosa (JM), and cecal content (CC). A total of 360 male, Ross 308 broiler chickens were allocated randomly into three treatment groups of 5 replicate pens with 24 chickens. Beside a corn and soybean meal-based control diet (C), a barley (B)- and oat (O)-based treatment was used. In all feeding phases, barley was fed at 40, while oats at 20% inclusion rate. At day 40, 10 birds per treatment were slaughtered and gut viscosity, the cecal short chain fatty acid (SCFA) concentration, and the microbiota composition of the different gut parts determined. In spite of the glucanase enzyme addition, the barley-based diet significantly increased the viscosity of the ileal content and this was also the diversity of the bacteriota in the small intestine. On the other hand, this treatment decreased the microbial diversity in the ceca and resulted in lower SCFA contents. Barley increased the abundance of the phyla Bacteroidetes and decreased that of Firmicutes and some of them genera in the JC and CC. Oats had only a slight effect on the measured parameters. The results highlight the importance of also taking into account the soluble fiber fractions of the feedstuffs in diet formulation and to adapt the exogenous enzyme supplementation of to the actual soluble fiber contents.

Changes in the cocoa shell dietary fiber and phenolic compounds after extrusion determine its functional and physiological properties

The influence of different extrusion conditions on the cocoa shell (CS) dietary fiber, phenolic compounds, and antioxidant and functional properties was evaluated. Extrusion produced losses in the CS dietary fiber (3–26%), especially in the insoluble fraction, being more accentuated at higher temperatures (160 °C) and lower moisture feed (15–20%). The soluble fiber fraction significantly increased at 135 °C because of the solubilization of galactose- and glucose-containing insoluble polysaccharides. The extruded CS treated at 160 °C–25% of feed moisture showed the highest increase of total (27%) and free (58%) phenolic compounds, accompanied by an increase of indirect (10%) and direct (77%) antioxidant capacity. However, more promising results relative to the phenolic compounds’ bioaccessibility after in vitro simulated digestion were observed for 135°C–15% of feed moisture extrusion conditions. The CS’ physicochemical and techno-functional properties were affected by extrusion, producing extrudates with higher bulk density, a diminished capacity to hold oil (22–28%) and water (18–65%), and improved swelling properties (14–35%). The extruded CS exhibited increased glucose adsorption capacity (up to 2.1-fold, at 135 °C–15% of feed moisture) and α-amylase in vitro inhibitory capacity (29–54%), accompanied by an increase in their glucose diffusion delaying ability (73–91%) and their starch digestion retardation capacity (up to 2.8-fold, at 135 °C–15% of feed moisture). Moreover, the extruded CS preserved its cholesterol and bile salts binding capacity and pancreatic lipase inhibitory properties. These findings generated knowledge of the CS valorization through extrusion to produce foods rich in dietary fiber with improved health-promoting properties due to the extrusion-triggered fiber solubilization.

Multi-Glycomic Characterization of Fiber from AOAC Methods Defines the Carbohydrate Structures.

Dietary fiber has long been known to be an essential component of a healthy diet, and recent investigations into the gut microbiome-health paradigm have identified fiber as a prime determinant in this interaction. Further, fiber is now known to impact the gut microbiome in a structure-specific manner, conferring differential bioactivities to these specific structures. However, current analytical methods for food carbohydrate analysis do not capture this important structural information. To address this need, we utilized rapid-throughput LC-MS methods to develop a novel analytical pipeline to determine the structural composition of soluble and insoluble fiber fractions from two AOAC methods (991.43 and 2017.16) at the total monosaccharide, glycosidic linkage, and free saccharide level. Two foods were chosen for this proof-of-concept study: oats and potato starch. For oats, both AOAC methods gave similar results. Insoluble fiber was found to be comprised of linkages corresponding to β-glucan, arabinoxylan, xyloglucan, and mannan, while soluble fiber was found to be mostly β-glucan, with small amounts of arabinogalactan. For raw potato starch, each AOAC method gave markedly different results in the soluble fiber fractions. These observed differences are attributable to the resistant starch content of potato starch and the different starch digestion conditions used in each method. Together, these tools are a means to obtain the complex structures present within dietary fiber while retaining "classical" determinations such as soluble and insoluble fiber. These efforts will provide an analytical framework to connect gravimetric fiber determinations with their constituent structures to better inform gut microbiome and clinical nutrition studies.

Effects of Probiotics and Wheat Bran Supplementation of Broiler Diets on the Ammonia Emission from Excreta.

Simple SummaryAnimal production is the main source of ammonia emission worldwide and all member countries of the European Union must reduce their national emissions. Among nutritional strategies, feeding low protein diets, using more nutritional phases, or using different feed additives can decrease the nitrogen excretion of animals and, in this way, lower the ammonia volatilisation from the manure. Pro- and prebiotics are widely used to improve gut health and to decrease the incidence of diseases. Numerous research findings have been published on the practical effects of pro- and prebiotics, but their impact on the urinary and faecal N excretion in chickens has not been completely clarified yet. In this research, the effects of using lactic acid and butyric acid producing bacterial strains, and wheat bran as a potential prebiotic, was tested with broiler chickens. Both probiotics increased the dry matter content and decreased the urinary N ratio of the excreta, which is positive from an ammonia emission point of view. Wheat bran and its xylan-oligosaccharides decreased both the ammonium -N content and the urinary N ratio. The results proved that beside the well-known nutritional techniques, the feed additives, which modify the gut microbiota and the fermentation in the caeca, can decrease the urinary-N excretion, and in this way lower the ammonia emission of broiler chickens.Ammonia emission is a concern for the poultry industry from both environmental and animal welfare points of view. The objective of this research was to determine whether probiotics or wheat bran supplementation of broiler diets can modify the N composition of the excreta and the dynamics of ammonia volatilisation emission from the manure. A total of 120-day-old Ross 308 broiler chickens were fed six different diets. The treatments included a corn and soybean meal-based control diet (C) and diets containing wheat bran (WB). Both diets were fed alone and with supplementation of a lactic acid (Lactobacillus farciminis, LAB) and a butyric acid (Clostridium butyricum, BAB) producing bacterial strain. Treatment BAB had a significant effect on the dry matter content of the excreta and both probiotics decreased the amount of excreted uric acid. Treatment WB resulted in a significantly lower NH+4-N concentration of excreta and a tendency toward reduced uric acid content. Treatment LAB reduced the urinary N ratio of excreta. Among dietary treatments, WB resulted in the highest urease producing cell numbers in the excreta, but this difference was not significant. Based on our results, similar to pigs, the soluble fibre fraction of poultry diets can also modify the urinary to faecal N ratio of the excreta.

Extrusion Processing of Rapeseed Press Cake-Starch Blends: Effect of Starch Type and Treatment Temperature on Protein, Fiber and Starch Solubility.

For the valorization of oilseed press cakes into food products, extrusion can be used. A common way of applying the protein- and fiber-rich press cakes in directly expanded products is the combination thereof with starch, since starch gives a favourable texture, which correlates directly to expansion. To control product properties like expansion of protein and fiber-rich extruded products, the underlying physicochemical changes of proteins, fibers and starch due to thermomechanical input need to be comprehensively described. In this study, rapeseed press cake (RPC) was extruded and treated under defined thermomechanical conditions in a closed-cavity rheometer, pure and in combination with four starches. The impact of starch type (potato PS, waxy potato WPS, maize MS, high-amylose maize HAMS) and temperature (20/25, 80, 100, 120, 140 °C) on protein solubility, starch gelatinization (Dgel), starch hydrolysis (SH) and fiber solubility of the blends was evaluated. The extrusion process conditions were significantly affected by the starch type. In the extruded blends, the starch type had a significant impact on the protein solubility which decreased with increasing barrel temperature. Increasing barrel temperatures significantly increased the amount of soluble fiber fractions in the blends. At defined thermomechanical conditions, the starch type showed no significant impact on the protein solubility of the blends. Therefore, the observed effects of starch type on the protein solubility of extruded blends could be attributed to the indistinct process conditions due to differences in the rheological properties of the starches rather than to molecular interactions of the starches with the rapeseed proteins in the blends.

Dried fruit pomace inclusion in poultry diet: growth performance, intestinal morphology and physiology

BackgroundFruit pomaces are by-products rich in polyphenol compounds and dietary fiber. They seem to play an important role in regulating the gut microbiota, morphology and physiology. The aim of this study was to assess whether apple (A), blackurrant (B) or strawberry (S) pomaces could be suitable ingredients in broiler diets and their effect on gut health. A total of 480 male broilers were randomly allotted to 8 dietary treatments with lower (3%-L) or higher (6%-H) dietary fiber content: two control groups (CL/CH), two A diets (AL/AH), two B diets (BL/BH), two S diets (SL/SH). Diet and fruit pomaces were chemically analyzed to assess polyphenol concentration and fibre fraction content. After the evaluation of growth performance, 6 birds/group were slaughtered at 35 days of age. Morphometric and histopathological investigations were performed on duodenum, jejunum and ileum. Excreta were collected to perform microbiota evaluation by 16S DNA sequencing. Weight, viscosity, enzymatic activity, short chain fatty acid (SCFAs) and ammonia concentration were determined in ileum and/or ceca content.ResultsA pomace and A diets showed the lowest polyphenol content and the highest content of soluble fibre fraction. No significant differences were observed for growth performance, gut morphometry and histopathology (P > 0.05). Dietary fruit pomace inclusion increased the weight of ileum and ceca and the ileum digesta viscosity (P < 0.05). In the ileum, A and S groups showed lower bacterial α-glucosidase activity than C groups. Moreover, small intestine SCFAs concentration was higher in fruit pomaces diets (P < 0.05). In ceca, B and S groups showed lower ammonia concentration and higher SCFAs than C. Dietary treatments also influenced the activity of α-glucosidase, α-galactosidase, β-galactosidase β-glucuronidase and xylase. Regarding microbiota, at phylum level, Firmicutes were differentially abundant across treatment (maximum for C and minimum in S, FDR > 0.05). At genus level, an increase of Weissella in AH and Erwinia in S/B diets, as well as a decrease of Lactobacillus in all fruit pomace groups were recorded (P < 0.05).ConclusionsFruit pomaces could be suitable ingredients in poultry nutrition even if further studies are needed to better understand which doses is more recommended to avoid negative effects on gut microbiota.

Time-Dependent Indirect Antioxidative Effects of Oat Beta-Glucans on Peripheral Blood Parameters in the Animal Model of Colon Inflammation.

Background: Oat beta-glucans are polysaccharides, belonging to soluble fiber fraction, that show a wide spectrum of biological activity. The aim of this study was to evaluate the time-dependent antioxidative effect of chemically pure oat beta-glucan fractions, characterized by different molar mass, which were fed to animals with early stage of 2,4,6-trinitrobenzene sulfonic acid (TNBS) - induced colitis. Methods: The study was conducted on 150 adult male Sprague Dawley rats assigned to two groups—healthy control (H) and colitis (C) with colon inflammation induced by per rectum administration of TNBS. The animals from both groups were divided into 3 nutritional subgroups, receiving for 3, 7 or 21 days AIN-93M feed without beta-glucan (βG−) or with 1% (w/w) low molar mass oat beta-glucan (βGl+) or 1% (w/w) high molar mass oat beta-glucan (βGh+). After 3, 7 and 21 days, the animals were euthanized, peripheral blood was collected from the heart for further analysis. Results: The results of analyses performed on blood samples showed small changes in lymphocytes count and red blood cell parameters such as the number of red blood cell, mean corpuscular hemoglobin concentration and mean corpuscular volume (RBC, MCHC, MCV respectively) as well as normalization of antioxidant potential accompanying moderate inflammatory state of colon mucosa and submucosa. Conclusion: Oat beta-glucans exert an indirect antioxidant effect in animals with TNBS-induced colitis, with greater effectiveness in removing systemic effects of colon inflammation found for low molar mass oat beta-glucan.

Colonic fermentation of water soluble fiber fraction extracted from sugarcane (Sacchurum officinarum L.) bagasse in murine models

Biochemical effects of the water soluble fiber fraction of sugarcane bagasse (BSF) fermented in the colon was examined to evaluate its potential health promoting effects. A feeding experiment involving Fischer 344 rats, was conducted with 3 experimental diets containing, cellulose (CON), a commercial xylo-oligosaccharide (XYO) and BSF (BGS). Cumulative feed intake was significantly lower in XYO group while cecal weight was significantly higher. Acetic and propionic acid contents in the cecal content were significantly higher in the BGS and XYO, respectively. Total short chain fatty acid content was significantly higher in BGS and XYO resulting significantly lower cecal pH. Beneficial bacteria such as Bifidobacterium, Blautia, Akkermansia and Roseburia abundance was significantly higher in the XYO and BGS groups. Further, mucin and immunoglobulin-A contents were significantly higher in BGS group compared to CON group. Thus, BSF exhibited its ability to enhance the intestinal and systemic health upon fermentation in the colon.

In vitro fermentation gas kinetics and end-products of soluble and insoluble cereal flour dietary fibres are similar.

Insoluble dietary fibre is often considered to be fermented slower and to a lesser extent in (models for) the colon than soluble dietary fibre. However these comparisons are typically made for fibre components of different composition. In the case of fibre from refined cereal flours, there is little difference in fibre composition between soluble and insoluble forms, so effects of solubility on fermentation can be tested without this confounding factor. For each of wheat, rye, and hull-less barley, soluble and insoluble fibre fractions from refined flour and models for baking and extrusion had comparable in vitro fermentation rates and extents, with similar levels of short chain fatty acid metabolites. This study suggests that there should be little difference in the large intestinal nutritional functionality of the soluble and insoluble fibre fractions from cereal grain flours, either unprocessed or after baking or extrusion processing.

Lentil flour formulations to develop new snack-type products by extrusion processing: Phytochemicals and antioxidant capacity

The effects of extrusion processing on fibre (soluble and insoluble), total available carbohydrates, tocopherols, organic acids, total phenolics, flavonols, hydroxycinnamic and hydroxybenzoic acids, as well as on the antioxidant capacity of different fibre-enriched lentil flours, were evaluated before and after extrusion process. Total dietary fibre was partially decreased after extrusion, which correlated with a significant increase in the soluble fibre fraction. γ-tocopherol was the major isoform, before and after extrusion. Additionally, a marked decrease of 83–94% in total tocopherols content after extrusion was observed. Conversely, an increase in most polyphenolic fractions was found, probably due to the effect of extrusion in the hydrolysis of polyphenols bound to fibre and proteins, with an increase in antioxidant activity. Only flavonols presented an extensive decrease (62–82%) after treatment. The novel pulse-based flours, enriched with gluten-free soluble and insoluble fibres, provide snack-type products with a balanced nutritional and antioxidants composition.

Impact of cooking and germination on phenolic composition and dietary fibre fractions in dark beans (Phaseolus vulgaris L.) and lentils (Lens culinaris L.)

The impact of cooking and germination on dietary fibre and phenolic compound composition was studied in beans (Phaseolus vulgaris L.) and lentils (Lens culinaris L.). An investigation on phenolic compounds in dietary fibre fractions was carried out due to the scarce literature on the behaviour of these compounds during legume processing. A general decrease in the concentration of insoluble and soluble fibre fractions were observed in processed bean and lentil flours, although an increase in the content of insoluble and soluble fibre fractions in sprouts and cooked beans, respectively, was found. Hydroxybenzoic and hydroxycinnamic compounds, flavan-3-ols, procyanidins, flavonols and flavones were identified in dietary fibre fractions in cooked and germinated beans and lentils. Phenolic compound constituents of the different dietary fibre fractions accounted from 73% to 97% in insoluble dietary fibre fraction (IDF) flours and from 3% to 25% in soluble dietary fibre fraction (SDF) in raw and processed bean and lentil flours. These processing techniques may produce positive changes in the dietary fibre and phenolic compound composition and its association could improve phytochemical and nutritional quality and maximize the health-promoting properties of legumes.

Effects of diverse food processing conditions on the structure and solubility of wheat, barley and rye endosperm dietary fibre

The effects of archetypal food processing conditions (dough formation, baking, extrusion, and cooking/boiling) on dietary fibre structure and extractability from the endosperm flours of rye, hull less barley and wheat are reported. For all flours and processes, the distributions of soluble/insoluble cell wall dietary fibre as well as the chemical composition (arabinoxylan (AX) branching patterns, β-glucan DP3/DP4 (DP = degree of polymerisation) ratios) of solubilised fractions were characterised. The results show that overall the total amounts of AX and β-glucan (BG) were not significantly affected by processing but that there were similar increases in the soluble fibre fraction (20–29%) for baked, extruded, and boiled/cooked processes for each flour, with lower (10–15%) increases for all flours processed into dough. In all cases, solubilised fractions of AX and BG had very similar chemical structures to the starting flour, suggesting that increased solubilisation was not due to specific chemical fractions. Confocal images illustrate loosely-held associations of β-glucan with the cell walls of processed foods in contrast to some of the arabinoxylans which appear more tightly held within the residual cell walls. The similarities in behaviour across the three grains are consistent with mechanical treatments during food preparation resulting in similar extents of disentanglement of physically-constrained AX and BG leading to their partial solubilisation.

Structural and functional characteristics of dietary fibre in beans, lentils, peas and chickpeas

To better understand the role that dietary fibre plays in the health benefits of pulses, the cell wall polysaccharides of pulses were characterized. To allow comparison between this data and nutritional studies, cooked chickpeas, lentils, beans and peas were used rather than raw seeds. Insoluble fibre, soluble fibre, resistant starch and oligosaccharide fractions were isolated using digestive enzymes at 37°C. Prebiotic galacto-oligosaccharides, including raffinose, stachyose and verbascose made up between 3.5 and 6.9% of the cooked pulses (dry weight basis). Pulse fibre is pectin rich, with most being found in the soluble fibre fraction. The soluble fibre fraction is a diverse mixture of polysaccharides of varying sizes and solutions of soluble fibre exhibit a range of viscosities depending on the pulse type. The sugars which make up the insoluble fibre fraction suggest a large cellulose component. Microscopic examination of cooked whole pulses showed that a large fraction of the starch was partially gelatinized and contained within intact cell walls whereas boiled flour pastes had few ungelatinized granules. After simulated upper-gut digestion, some starch remained inaccessible to digestive enzymes. Cell walls of pulses modulate starch gelatinization and reduce enzymatic hydrolysis, which may account for the low glycemic response attributed to pulses.