In vitro fermentation of beet fibre and barley bran,of their insoluble residues after digestion and of ileal effluents

The main objective of this study was to determine the form in which beet and barley bran fibres reach the colon, and to evaluate the influence of endogeneous compounds on their patterns of fermentation. Raw fibres (RF), corresponding ileal effluents (IE) from pigs, and insoluble fibre residues (IR) extracted from IE, were fermented with human faecal inoculum for 24 h in an in vitro batch system. For beet fibre, rate but not extent of cell wall sugars degradation was increased (+34% at 6 h, P<0·05) after oroileal transit, due to a more porous structure. For barley bran, oroileal conditions degraded endosperm compounds such as β-glucans, leading to a lower extent of cell wall glucose fermentation compared with RF (-22% at 24 h, P<0·05). In the presence of endogeneous substances, degradation of beet fibre polysaccharides was delayed (P<0·05) at each incubation time but that of barley bran fibre was unaltered. Compared to RF, IR and IE significantly exhibited lower acetate production for beet fibre, and higher propionate and lower butyrate production for barley bran after 24 h. It is concluded that in vivo digestion modified fermentation patterns of both fibres in a manner depending on botanical structure. ©1997 SCI     

Analysis of dietary fibre.

An analytical procedure for the determination of dietary fibre in food is described. The method consists of an enzymic in vitro digestion with pepsin, pancreatin arid glucoamylase. Insoluble fibres are recovered by centrifuging and soluble fibres by precipitation with ethanol. The method has been applied to 19 cereal fibres, vegetables and fruits and compared to the neutral and acid detergent methods. The soluble fibres accounted for 4–60% of the total dietary fibre. The component sugars and uronic acids of several fibre fractions have been quantitatively determined. The mild biochemical treatment of the samples makes it possible to study further physical properties of dietary fibres important for their physiological action.     

The degree of polymerization of inulin-like fructans affects cecal mucin and immunoglobulin A in rats

ABSTRACT:  Cecal amounts of mucin and immunoglobulin A (IgA) were examined through the cecal fermentation pattern in Wistar (WS) or Sprague–Dawley (SD) rats fed inulin-type fructans differing in their degree of polymerization (DP). The animals were fed a control diet or a diet containing one of the fructans with an average DP of 4, 8, 16, or 23, at 60 g/kg diet for 10 d. Cecal fermentation products substantially differed between WS and SD rats fed DP8 fructan, with short-chain fatty acids (SCFAs) as the major organic acids in the former but lactate predominating in the latter. Cecal fermentability of fructans in both strains generally decreased with increasing DP of fructans, and this was especially manifest in reduction of the amounts of lactate in DP16 and 23. In WS rats, cecal mucin and IgA were greater in all fructan groups than in the control group. In SD rats, cecal mucin was greater only in the DP8, 16, and 23 groups as compared to the control group, while IgA was greater in the DP4 and 8 groups. In both strains, cecal mucin correlated with the sum of cecal SCFAs, but not with lactate, succinate, or total organic acids. In contrast, only cecal lactate correlated with cecal IgA in both strains. The present study shows that the different fermentation patterns of fructans affect cecal mucin and IgA; mucin is likely to respond to cecal SCFA production, whereas IgA increases when fermentation occurs rapidly and lactate is a major fermentation product.     

pH and dose-dependent effects of quercetin on the fermentation capacity of Lactobacillus plantarum

This article reports a study of how quercetin affects the capacity of Lactobacillus plantarum RM71 to ferment different media, including a chemically defined medium (CDM) and media relevant for practical fermentation processes. It is shown for the first time that quercetin exerts pH- and dose-dependent effects on the fermentation performance of L. plantarum. At an initial pH of 5.5, quercetin promoted quicker growth upon inoculation at increased quercetin concentrations, while a detrimental dose-dependent lengthening of the lag phase was observed at an initial pH of 6.5. The time course of sugar consumption and lactic acid production data tracking in pH 5.5 CDM showed that quercetin promoted quicker sugar consumption as a result of earlier sugar uptake and lactic acid production than in the control. A model wine and a similar medium with modified sugar composition were fermented with L. plantarum RM71 on quercetin. Quercetin improved several key fermentation traits for the performance of L. plantarum in food production, including accelerated fermentation of various sugars, and accelerated malolactic fermentation and lactic acid production. Quercetin was not catabolized by L. plantarum in the fermentations, so the antioxidant properties of the flavonol were protected against degradation while the bacterium improved its growth performance.     

Chemical composition and dietary fibre of yellow and green commercial soybeans (Glycine max)

Proximate composition and dietary fibre (as non-starch polysaccharides) of yellow soybeans (from conventional, ecological, transgenic and non-transgenic crops) and green soybeans (from conventional and ecological crops) has been studied. Dietary fibre, fat and ash were significantly higher in yellow than in green samples, but moisture and available carbohydrates were significantly lower in yellow soybean than in green ones. Few statistical differences were found for protein between different samples. Soybean seeds were rich in dietary fibre (yellow: 13.7–16.5 g/100 g, green: 9.19–9.45 g/100 g). This component was evaluated as insoluble and soluble fibre, and subsequently, the neutral sugars and uronic acids were determined by gas liquid chromatography and spectrophotometry, respectively. Insoluble fibre became the predominant fibre fraction in yellow and green soybeans (74–78%), and was mainly composed of glucose, uronic acids, galactose, arabinose and xylose. Soluble fibre was between 22% and 26% in both kinds of samples and the principal monomers were uronic acids, galactose and arabinose. The major difference between total dietary fibres of yellow and green commercial samples was the proportion of galactose, which was an important constituent in yellow soybeans (21%) and a minor one in green soybeans (5%).     

Fruit‐based functional foods I: production of food‐grade apple fibre ingredients

With the increased consumer interest in fibre‐enriched functional foods, industrial‐scale methods for functional fibre production are demanded. The development of a food‐grade fibre preparation method at lab scale that is feasible for industrial scale‐up is a pre‐requisite. This paper describes two lab‐scale fibre preparation methods that have potential to be scaled up to industrial setting for the production of fruit fibres containing desired bioactives and functionality. The two methods, one aqueous and the other ethanolic, were used to isolate fibres from Granny Smith apples (Malus domestica Borkh cv. ‘Granny Smith’). In the aqueous method, ground apple tissues were suspended in HEPES buffer (20 mM, pH 6.5), and then mechanically ruptured using an Ultra‐Turrax and ring grinder. Between steps, the cell‐wall materials were washed with the HEPES buffer. In the ethanolic method, ground apple tissues were stirred in 72% ethanol at 4 °C, filtered, re‐suspended in 72% ethanol and then washed. Microscopic examination and chemical analysis were performed on the resultant fibres. The aqueous method produced natural and uniform dietary fibres in the form of plant cell walls containing 0.282 g uronic acid per g dried fibre. By comparisons, the ethanolic method produced crude fibres containing only 0.182 g uronic acid per g dried fibre, the lower uronic acid content indicating the presence of impurities. Thus, the aqueous method appeared to be advantageous in terms of the retained pectic polysaccharide content and cost‐effectness for industrial scale‐up. Further characterisation using Folin‐Ciocalteu assay and high performance liquid chromatography indicates that the fibres obtained by the aqueous method contained significant amounts of phenolic compounds (2.6 mg catechin equivalent per g dried fibre). These results suggest that fibres obtained by the aqueous method may be more suitable for functional food applications where fibres with high pectic polysaccharide and beneficial phenolic antioxidants are preferred.     

Hydrolysis of fructans from Agave tequilana Weber var. azul during the cooking step in a traditional tequila elaboration process

In traditional tequila production, the heads of Agave tequilana Weber var. azul are cooked in brick ovens to hydrolyze the fructan content and release fermentable sugars. The juice generated during cooking (known as “cooking honey”) was collected periodically in a tequila distillery and characterized to study the efficiency of fructan hydrolysis. The complex structure of fructans from A. tequilana was confirmed. The generation of 5-(hydroxymethyl)-furfural, an increase in absorbance and °Brix, and a decrease in pH and apparent average degree of polymerization of fructans during cooking were observed. The conversion of fructans in the flowing honey increased gradually from 20% at the onset of cooking to 98% after 25.5 h, where fructose represented more than 80% of the total carbohydrates. The proportion of non-hydrolyzed fructans in the cooking honey collected before this time resulted in a total ethanol loss of 6% in the tequila distillery investigated.     

Human Colonic Bacterial Degradability of Dietary Fibres from Sea-Lettuce (Ulva sp)

Sea-lettuce (Ulva sp) is one of the commonly consumed seaweeds which contains 16·5% of water-soluble and 13·3% insoluble dietary fibres. Since physiological effects of fibres are partly related to their colonic bacteria fermentability, Ulva sp and its constitutive soluble and insoluble fibres were incubated with faecal bacteria in an in vitro batch fermenter system. After 24 h of incubation, 32·0±0·4%, 25·9±0·4% and 50·9±7·4% of Ulva, soluble and insoluble fibres constitutive sugars, respectively, were degraded. Consequently, Ulva and its soluble fibre, ulvan, are poorly fermented by colonic bacteria. The constitutive sugars, rhamnose and glucuronate and the aldobiouronate β-D -glucuronosyluronate-(1,4)-L -rhamnose of the glucuronoxylorhamnan sulphate present in the soluble fibre are highly fermented. Chemical desulphation and/or carboxyl group reduction did not modify this fermentation behaviour. Thus, the particular chemical structure of ulvan is responsible for the resistance of this polysaccharide and of Ulva to colonic bacterial fermentation. As a physiological consequence of this particular behaviour, consumption of dietary fibres from sea-lettuce could be expected to act mainly as bulking agents with little effect on nutrient metabolism due to colonic bacterial fermentation products (short-chain fatty acids). © 1997 SCI.     

Neutral-sugar determination by HPAEC-PAD to characterise polysaccharide degradation by colonic bacteria

 In vitro methods are widely used to characterise dietary fibre fermentability in the human hind gut. The activity of faecal bacteria can be followed by measuring fermentation products and substrate degradation. This paper describes a method for establishing neutral-sugar profiles by HPAEC-PAD during in vitro fermentation studies. Freeze-dried fermentation residues are hydrolysed with H₂SO₄, and the monomers are separated on an anion-exchange column using a reverse NaOH gradient. Sulphate ions are removed from hydrolysates on-line with a special ion-exchange guard column. 2-D-deoxyribose is used as internal standard for quantification. A method for separating all neutral sugars that typically occur in dietary fibre is given. Possibilities for enhancing the resolution for other purposes are suggested. Compared to GC the described method is particularly attractive for routine analyses. Data relating to the decreasing levels of neutral sugars in fermentation residues of oat bran fractions that differ in their mixed-linked β-glucan content are given and degradation patterns of the polysaccharides present in these substrates are discussed. Received: 26 February 1997     

Effect of chemical treatments of sugar beet fibre on their physico-chemical properties and on their in-vitro fermentation

Chemically treated and dried sugar beet fibres were fermented in vitro in order to study the effects of chemical and physico-chemical parameters of dietary fibre on their colonic fermentation. Sugar beet fibre was treated with dilute alkali, removing mainly acetyl and methyl ester groups, and/or with dilute acids eliminating arabinose, galactose and certain uronic acid residues. The chemical treatments led to an increase in the hydration properties and fermentability by improvement of the accessibility of the remaining polysaccharides. However, if the chemically treated fibres were dried under harsh conditions (100°C), their hydration properties and their fermentability were limited, probably because of structural collapse of the fibre matrix. Whatever the conditions for chemical treatments and drying of the sugar beet fibres, it was possible to predict their fermentability from the water-binding capacity. Because of the relationship between the physiological effects of dietary fibres and the extent to which they are fermented, this result underlines the importance of the physico-chemical characterisation of the fibre in order to acquire a better knowledge of their physiological effects.     

Physicochemical Properties of Dietary Fibres Prepared from Ambarella (Spondias cytherea) and Mango (Mangifera indica) Peels

The preparation of fibres from mango and ambarella peels can offer a way to upgrade by-products. Comparatively to lime, ambarella and mango fibres were prepared from their corresponding peels using ethanolic treatment (85% at 70 °C/5 min). The peels were characterised for their dry matter content, pH and apparent viscosity. The soluble dietary fibre (SDF) and insoluble dietary fibre (IDF) contents of the samples were determined. Hydration capacity of these fibres was evaluated. Results showed that the ethanolic treatment of the peels (85% at 70 °C/5 min) had significant (p?<?0.05) effects on the contents of neutral sugars and uronic acid (from 105 to even 203 mg/g in case of mango fibre). For ambarella fibres, the proportion of IDF (51%) was highest and that of SDF (34%) was lowest. Mango and lime fibres exhibited similar values of IDF (40–43%) and SDF (50–57%). Mango peel fibres had higher hydration capacities than ambarella and lime fibres. The best dietary fibres content and the high hydration capacities of mango peel fibres favour their exploitation in dietary fibre-rich foods preparation.     

In vitro fermentation of polysaccharides of rye,wheat and oat brans and inulin by human faecal bacteria

The in vitro fermentabilities of rye, wheat and oat brans and of a commercial fibre preparation, inulin, were compared. The brans were first digested enzymatically to remove starch and protein. The digested brans and inulin were then fermented with human faecal inoculum. The progress of fermentation was studied by following the consumption of carbohydrates and the production of short‐chain fatty acids and gases. Inulin, a short fructose polymer, was consumed significantly faster than the more complex carbohydrates of cereal brans. Carbohydrates of oat bran (rich in β‐glucan) were consumed at a higher rate than those of rye and wheat brans (rich in arabinoxylan). In all brans, glucose was consumed faster than the other main sugars, arabinose and xylose, and arabinose was degraded only slightly. The total production of short‐chain fatty acids was slightly higher with oat bran than with rye and wheat brans and inulin. In the fermentation of inulin, relatively more butyric acid and less propionic acid were produced than in the fermentation of brans. The decrease in pH was also greater in the case of inulin. Wheat bran led to a slightly slower gas formation than rye and oat brans. Formation of gases was fastest and greatest in the case of inulin. In conclusion, rye, wheat and oat brans were fermented in a rather similar way. Fermentation of the brans was different from that of inulin. Cereal brans might serve as a more balanced source of dietary fibre supplement than gas‐producing, readily fermentable polysaccharides such as inulin. © 2000 Society of Chemical Industry     

Evaluation of Brazilian ethanol production yeasts for maltose fermentation in media containing structurally complex nitrogen sources

Maltose and glucose fermentations are strongly affected by the structural complexity of the nitrogen source and by the presence of oxygen. In this study five industrial Saccharomyces cerevisiae strains were grown in synthetic medium, containing maltose or glucose, supplemented with different nitrogen sources, with or without agitation. All strains were able to grow and efficiently ferment glucose, but not all strains were able to grow and ferment maltose well. Peptone and ammonium sulfate induced improved fermentation for all strains and conditions. Under agitation, as expected, higher biomass accumulation was detected. Casamino acids supplementation induced efficient maltose fermentation for all of the strains under aerated conditions, but differing maltose utilization patterns were observed for the static cultures. Copyright © 2012 The Institute of Brewing & Distilling     

A Consistent Inoculum System to Study the Fermentation of Non-starch Polysaccharides

A variable in batch culture fermentation systems for studying the fermentation of polysaccharides is the faecal inoculum. A commercial bacterial bead preservation system (Microbank^TM) has been used for the long-term storage of faecal inoculum. The inoculated beads are stored at -70°C for up to 3 months and retain their ability to ferment pectin, as measured by production of short-chain fatty acids. A recovery medium is used for 27 h followed by culture in a standard medium for 48 h. Such a system offers a significant advantage over the present method of using fresh faeces on each occasion both in terms of ease of use and consistency of the inoculum. This allows for repeatable fermentation experiments over prolonged periods of time. © 1997 SCI.     

Influence of chemical and physical modification on the bile acid binding capacity of dietary fibre from lupins (Lupinus angustifolius L.)

Bile acid adsorption by dietary fibre in the human intestine is widely considered to be a mechanism for lowering the blood cholesterol level and reducing the risk of colon cancer. In this study, the influence of physical and chemical treatment on the bile acid binding capacity of lupin dietary fibres was determined in vitro. Various methods for modifying dietary fibres were investigated (enzymatic, acid, and alkaline hydrolysis, as well as acetylation). The bile acid binding capacity was measured using an enhanced in vitro digestion model. The native lupin fibre product showed a bile acid binding capacity of 19%, whilst the medication cholestyramine exhibited a binding capacity of almost 100%. Enzymatic and acid hydrolysis caused a significantly increased binding capacity of up to 38%, corroborating the importance of dietary fibre structure, composition, and degree of degradation as determining factors for the bile acid binding capacity. The results of the acetylation experiments support the hypothesis of a hydrophobic linkage between bile acids and dietary fibre. Furthermore, the binding capacity depends on the particle size distribution, and consequently on the particle specific surface area.     

A rapid method for determining the carbohydrate component of dietary fibre

A simplified procedure for the determination of the non-starch polysaccharides in foods is described. Starch is removed by treatment with heat-stable α-amylase and resistant starch by treating with dimethyl sulphoxide (DMSO) and amyloglucosidase. Total neutral sugars and uronic acids are then measured colorimetrically in the acid hydrolysates of the starch-free material.The method is more rapid than the complex fractionation procedures (Southgate, 1969; Selvendran et al., 1979; Englyst, 1981) but does not provide a detailed composition. The time per sample compares favourably with the gravimetric assay of Asp et al. (1983) and a direct measure of the carbohydrate content of the dietary fibre fraction is obtained. The results compare favourably with those obtained by the complex method of Englyst et al. (1982). The method is applicable to a range of foods, both raw and cooked, and should have application in the routine analysis of dietary fibre since it is comparatively rapid and does not require complex or expensive equipment.     

Chemical composition and functional properties of Ulva lactuca seaweed collected in Tunisia

The chemical composition and some functional properties of the dried “Ulva lactuca” algae, collected from the littoral between the Taboulba and Sayada area, were determined. The dried “U. lactuca” algae were investigated for their soluble, insoluble and total dietary fibre content, mineral amount, amino acid and fatty acid profiles, swelling capacity (SWC), water holding capacity (WHC) and oil holding capacity (OHC). Results showed that “U. lactuca” alga powder was characterised by a high content of fibres (54.0%), minerals (19.6%), proteins (8.5%) and lipids (7.9%). The neutral fibres contain hemicellulose (20.6%), cellulose (9.0%) and lignin (1.7%). The proteinic fraction analysis indicated the presence of essential amino acids, which represent 42.0% of the total amino acids. The fatty acids profile was dominated by the palmitic acid, which represents about 60.0% of the total fatty acids, followed by oleic acid (16.0%). The study of the functional properties proved that SWC, WHC and OHC of this alga varied with temperatures and that were comparable to those of some commercial fibre rich products.     

Fructans,water‐soluble fibre and fermentable sugars in bread and pasta made with ancient and modern wheat

The aim of this study was to determine wheat constituents in bread and pasta that might result in intestinal gas production. Fructans, water‐soluble arabinoxylans, arabinogalactan proteins and fermentable sugars were followed in bread and pasta made with ancient (Khorasan wheat; emmer) and modern wheats (common wheat; durum). After fermentation for 180 min, 80% of fructans were eliminated and higher levels of fructose than glucose accumulated in bread dough supplemented with sucrose. Whole‐grain Khorasan wheat and emmer flours inhibited yeast fermentative activity. Half of fructans, arabinogalactan proteins and sugars were washed out in cooking water for pasta. Water‐soluble wheat arabinoxylans increased in bread and cooked pasta. With very low levels (0.3–0.8%, dry basis), fructans in cooked pasta and, in particular, long‐fermentation bread prepared with modern or ancient wheat would unlikely act as major gas‐forming triggers of gastrointestinal discomfort associated with noncoeliac gluten sensitivity.     

Improve the functional properties of dietary fibre isolated from broccoli by-products by using different technologies

The aim of this study was to analyze the chemical composition of leaves, stems and inflorescences obtained from broccoli by-products in order to develop the improvement of the composition and functional properties of DF from broccoli by-products through treatment with different degradation methods, such as modifications with supercritical fluids, enzymatic, autoclave and ultrasound treatment. The results showed that the chemical composition of the different parts of the broccoli by-products, leaves, stems and inflorescences was significantly different, highlighting that the content of insoluble and soluble dietary fibre was higher in the stem. The enzymatic treatments decreased the content of neutral sugars and increased the content of uronic acids, which was related to the increase of specific functional activities. Cellulase and the multi-enzymatic visconzyme complex improved the solubility and glucose adsorption capacity, whereas supercritical fluids treatment improved the swelling, water retention and lipid absorption capacities. The value of non-extractable phenolic compounds was higher in the inflorescences and increased with enzyme and supercritical fluid treatments, as well as the antioxidant capacity. Enzyme treatment also had a greater effect on the stimulation of the growth of the lactic acid bacteria studied and, therefore, reached the highest values in the production of all short-chain fatty acids analysed. Therefore, the use of enzyme treatments of dietary fibre obtained from broccoli by-products improves the functional properties of broccoli fibre.     

Soluble dietary fibres from sugarcane bagasse

Soluble dietary fibres from sugarcane bagasse were extracted under alkaline conditions and characterised. Precipitated fibres were dialysed, and the fibre composition was evaluated before and after the dialysis step. Compositional analysis indicated that the fibres both before and after dialysis consisted of 39% w/w total sugars, 16% w/w protein, 10% w/w Klason lignin and 30% w/w ash. Xylose was the main neutral sugar followed by arabinose with glucose, galactose and uronic acids also present in all samples. The structural properties were also spectroscopically examined, which confirmed the presence of arabinoxylans. Macromolecular characterisation revealed that molecular weight is reduced after dialysis, indicating that a range of dietary fibres with different macromolecular characteristics may be obtained depending on the specific processing steps. The present work shows that soluble arabinoxylans may be obtained from sugarcane agricultural wastes that may be used as a source of novel dietary fibres.