Effects of simulated digestion in vitro on cell wall polysaccharides from kiwifruit (Actinidia spp.)

Cell wall polysaccharides are resistant to digestion and absorption in the human small intestine and are considered to be delivered to the colon in a chemically unaltered state. In this paper, pulp from green and gold kiwifruit was subjected to in vitro upper-intestinal tract digestion and the chemical and physical changes to cell wall polysaccharides (dietary fibre) were investigated. Yields of insoluble fibre decreased slightly with simulated digestion while soluble fibre yields increased. Constituent sugar and glycosyl linkage analysis of the soluble and insoluble fibre fractions revealed that the chemical composition and structure of the non-starch polysaccharides remained largely unchanged. However, the degree of methylesterification of galacturonic acid residues present in the pectin-rich soluble fibre fractions of both fruit decreased with treatment; size-exclusion chromatography detected changes in the molecular weight profiles of these fractions. These changes may affect the physicochemical properties and fermentability of kiwifruit dietary fibre in the large intestine.     

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     

Studies on dietary fibre. A method for the analysis and chemical characterisation of total dietary fibre

A procedure for the analysis of total dietary fibre (including non-starchy polysaccharides and Klason lignin) is described. The method consists of extraction of homogenised and/or milled foodstuffs with 80% ethanol and chloroform, and analysis of acidic and neutral polysaccharide constituents, starch and Klason lignin in the residue. Uronic acid constituents were determined by a decarboxylation method, neutral sugar constituents as alditol acetates by a gas-liquid chromatographic method, starch by an enzymic method, and Klason lignin gravimetrically. The sum of anhydrosugars, anhydrouronic acids and Klason lignin from which the starch content is subtracted provides a measure of the total dietary fibre. The method described is reproducible, fairly rapid and gives informative quantitative characterisation of the fibre constituents.     

Breakdown of plant carbohydrates in the digestive tract of pigs fed on wheat‐ or oat‐based rolls

Cell wall materials from various cellular tissues of cereals may potentially influence the digestion and absorption processes in different ways. The objective of the present investigation was to study the breakdown of plant carbohydrates in the gastrointestinal tract of pigs fed a low‐fibre (LF; 65 g kg⁻¹ dry matter) wheat flour‐based diet and two high‐fibre diets with added insoluble fibre from wheat bran (HFWB; 112 g kg⁻¹ dry matter) or soluble fibre from oat bran (HFOB; 108 g kg⁻¹ dry matter). The diets were formulated to provide ∼0.31 energy from fat, ∼0.18 energy from protein and ∼0.51 energy from carbohydrates and were offered as baked rolls to eight ileum‐cannulated hypercholesterolemic pigs in a crossover design. Carbohydrates were the predominant ileal constituent, with most of the carbohydrates present as non‐starch polysaccharides (NSP). Starch in all diets was almost completely digested at this site of the gastrointestinal tract, with digestibility values above 0.99. The ingested amount of NSP was quantitatively recovered in ileal materials with the wheat‐based diets, while there was a significant loss of 0.27 of NSP primarily as mixed linked (1→3)(1→4)‐‐D ‐glucan with diet HFOB. The concentration and flow of lactic acid were also highest in the ileum after feeding diet HFOB, indicating that ‐glucan stimulated lactic acid formation. Any soluble components that reached the large intestine were almost completely broken down, while the digestibility of insoluble NSP constituents was significantly lower for diets LF and HFWB than for diet HFOB. The high degradation of oat bran resulted in a lower effect on faecal dry and wet bulking than was found with wheat bran. In conclusion, cereal starch was practically completely degraded in the small intestine, while the site and extent of NSP degradation, lactic acid formation and bulking properties were influenced by the fibre source. © 2000 Society of Chemical Industry     

Effect of Callosobruchus chinensis (L.) (Coleoptera: Bruchidae) on carbohydrate content of chickpea,green gram and pigeon pea

Effect of Callosobruchus chinensis (L.) infestation was seen on the carbohydrate and dietary fibre content of chickpea, green gram and pigeon pea at 10, 20, 30, 40, 50 and 60 per cent levels of infestation. With increase in level of infestation energy, starch, total sugars and non-reducing sugars decreased, whereas significant increase in the reducing sugars, crude fibre, neutral detergent fibre, acid detergent fibre, hemicellulose, cellulose and lignin was observed.     

The analysis of dietary fibre—the choices for the analyst

The analysis of dietary fibre (which is defined as the sum of lignin and the polysaccharides not digested by the endogenous secretions of the human digestive tract) presents several problems to the analyst. Dietary fibre is a mixture of substances derived from the structural materials of the plant cell wall and a range of polysaccharides of a non-structural nature either present naturally in foods or derived from food additives. The complete analysis of such a complex mixture would be difficult and time consuming and a number of practical alternatives have been used. These include methods based on the enzymatic removal of protein and starch to give an ?indigestible residue’? and procedures based on extraction with neutral detergent solutions. These procedures in their present form do not measure water-soluble components and therefore underestimate dietary fibre. More detailed methods in which the water-soluble and water-insoluble non-cellulosic polysaccharides, cellulose and lignin were measured separately are described. In these the non-cellulosic fraction was characterised in terms of its component sugars. It is suggested that methods of this type are necessary to characterise dietary fibre analytically in order to account for the properties of dietary fibre.     

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     

Determination of Neutral Detergent Fiber in Breakfast Cereals: Pentose, Hemicellulose, Cellulose and Lignin Content

Cereals are often promoted as important sources of dietary fiber. Ninety one breakfast cereals available in Canada and four unprocessed wheat brans were therefore analyzed for neutral detergent fiber (NDF) after rapid digestion with α-amylase from porcine pancreas. Many breakfast cereals contained less than 5% NDF. Wheat cereals contained 5–30% NDF, oat cereals contained 5% NDF, and corn and rice contained little NDF. Cereal NDF was predominantly hemicellulose (pentosans); pentose sugars liberated under hydrolysis represented up to 15% of processed bran cereals and 20–25% of unprocessed bran.     

Analysis of carbohydrates in seven edible fruits of Bangladesh

Dry matter, ash, lignin, starch and soluble and insoluble dietary fibre contents of the edible parts of seven fruits of Bangladesh were determined. Analysis of the low molecular weight carbohydrates showed that all the fiuits, except lukluki and hogplum, contained substantial amounts of these materials of which glucose and fiuctose were the main components. The main constituent of the polysaccharides in all the fruits was glucose. The dietary fibre contents of the dry fruits ranged from 29% to 79%. Lukluki has by far the best combination of low fiee sugars and high dietary fibre, and pineapple the worst.     

Analysis of carbohydrates in the jute plant (Corchorus capsularis)

Jute plants (Corchorus capsularis) were fractionated into bark and stick. Jute fibre was produced from the bark by retting in water. Polysaccharides and lignin (estimated as Klason lignin) were the major constituents of the three jute fractions. Glucose, fructose, sucrose, six low-molecular weight sugar alcohols (glycerol, erythritol, threitol, rhamnitol, arabinitol, and mannitol), and two inositols (myo-inositol and scyllitol) were identified and quantified in the bark; all these compounds, except rhamnitol were also measured in the stick. Cellulose, xylans and pectins were major polysaccharide constituents in the three jute fractions. During fibre production by retting, extractives and pectic polysaccharides were solubilised or degraded, producing a fibre material enriched in cellulose and xylans.     

Production and characterisation of two wheat-bran fractions: an aleurone-rich and a pericarp-rich fraction

Wheat bran is a good source of dietary fibre in the form of cell walls, but contains a number of different cell types. We describe a large-scale procedure for the production of an aleurone-rich and a pericarp-rich fraction from hard, Australian wheat. The fractions were characterised by field-emission scanning electron microscopy, by using a range of bright-field stains, colour reagents, and fluorochromes, and by chemical analysis of the walls. The aleurone fraction included the seed coat with its cuticle. Only the pericarp walls showed a histochemical reaction for lignin. The concentrations of ester-linked ferulic acid and (1-->3),(1-->4)-beta-glucans were greater in the aleurone-rich fraction than in the pericarp-rich fraction. The results are consistent with the arabinoxylans in the walls of the pericarp-rich fraction being more highly substituted with arabinose than those in the walls of the aleurone-rich fraction. When the fractions were fed as a dietary supplement to rats and walls were isolated from the faeces, it was found that the pericarp walls were not degraded, but the aleurone walls were partially degraded.     

Polyphenol and nutrient release from skin of almonds during simulated human digestion

The bioaccessibility of nutrients and phytochemicals from almond skin has not been previously evaluated. We quantified the release of lipid, protein and polyphenols during simulated human digestion from natural (NS) and blanched (BS) skins, the latter being a by-product of the almond industry. Higher percentages of polyphenols were released from NS compared to BS during in vitro digestion. Most of the limited release of lipid and protein occurred during gastric digestion, with no significant differences between NS and BS. The total dietary fibre content was 45% for NS and 46% for BS, glucose and galacturonic acid being the major sugars present. No changes in dietary fibre composition and distribution of autofluorescent phenolics were observed in the cell walls of almond skin after simulated digestion. In the GI tract, the cell walls may therefore function as a useful source of fermentable fibre with beneficial implications for gut health.     

Comparative studies between the optimum dietary fibre sources of some substituted cookies

To realize the line of balance between utilization of dietary fibre sources level of substitution and maximum improvement or minimum reduction of in vitro protein digestibility in high dietary fibre cookies, the optimum level of substitution by corn bran, rice bran and barley husk were studied. Analysis for amino acids composition, infrared absorption spectroscopy and X-ray diffraction were carried out. Rice bran was the best fibre source for improving lysine content. Barley husk fulfilled two criteria viz. improvement in lysine content and minimum decrease in amino acids content.     

蒸汽爆破处理苦荞麸皮膳食纤维改性分析

目的：为了提高苦荞麸皮膳食纤维的综合利用率,采用蒸汽爆破技术对苦荞麸皮进行预处理,探究不同蒸汽爆破压力及保压时间对苦荞麸皮膳食纤维改性的影响。方法：以可溶性膳食纤维含量为主要指标得到最优蒸汽爆破改性条件,并对改性前后苦荞麸皮可溶性和不溶性膳食纤维的单糖组成、可溶性膳食纤维的理化性质及结构特性进行分析。结果：蒸汽爆破处理后,苦荞麸皮不溶性膳食纤维、纤维素、半纤维素、木质素及果胶含量显著降低（P＜0.05）,可溶性膳食纤维、可溶性糖、还原糖含量及总糖含量显著提高（P＜0.05）;最佳蒸汽爆破改性条件为1.2 MPa、90 s,在该条件下可溶性膳食纤维含量（12.36 g/100 g）较未蒸汽爆破处理（8.02 g/100 g）提高了54.11%;经最佳条件蒸汽爆破处理后,苦荞麸皮膳食纤维单糖组成发生改变,可溶性膳食纤维的持水力、持油力、膨胀力、α-淀粉酶活性抑制能力、葡萄糖吸收能力及热稳定性增强;可溶性膳食纤维羟基基团暴露增加,并呈现疏松多层蜂窝式网状结构。结论：蒸汽爆破预处理有助于提高苦荞麸皮可溶性膳食纤维含量,改善其理化结构特性,可为苦荞麸皮可溶性膳食纤维的利用及保健食品开发提供理论参考。     

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     

Degradation of cell wall material of apple and wheat bran by human faecal bacteria in vitro

The effect of the structures of plant cell walls and their component polymers on the degradability of dietary fibre by bacteria of the human colon was investigated by inoculating culture media containing cell wall materials of apple and wheat bran with slurries of human faeces which were then incubated for periods of up to 72 h. In the apple substrates the amounts of pectic polysaccharides were extensively depleted after 12 h, and after 24 h over 90% of the initial carbohydrate had been degraded. Material which remained after incubation was probably comprised of highly branched fragments of rhamnogalacturonans, cross-linked by phenolics and proteins, highly branched fragments of cross-linked xyloglucans, and degraded cellulose. In wheat bran the aleurone layer was preferentially degraded, but the glucuronoarabinoxylans, which were cross-linked by phenolic groups, and the lignified outer layers of the bran were very resistant to attack. Bacteria adhered mainly to the broken or damaged surfaces of the plant cell walls, and in the more resistant tissues only penetrated the intercellular regions.     

高活性玉米膳食纤维的制备、性质与应用

以玉米种皮为原料,采用酶法制得高活性玉米膳食纤维（ＨＡＦＣ）,含有１２．６９％水溶性纤维,４４．８１％半纤维素,１３．０５纤维素与７．０４％木质素,膨胀力与持水力分别为６．５ｍｌ／ｇ和６２０％。详细论述了玉米膳食纤维的制备方法,化学成分、物化性质及在食品中的应用。     

固态发酵麦麸对面团及面条品质的影响

本文使用乳酸菌和酵母菌发酵麦麸,通过糊化特性、动态流变学、面条质构特性和体外消化等指标来探究固态发酵麦麸对面团以及面条品质的影响。结果表明,发酵麦麸的不溶性膳食纤维含量显著降低（P<0.05）,可溶性膳食纤维、可溶性阿拉伯木聚糖（WEAX）和多酚含量显著提高（P<0.05）。与未发酵麦麸组相比,发酵麦麸组面团的峰值粘度和谷值粘度增加;弹性模量（G’）和粘性模量（G"）增大,tanδ和蠕变柔量（J）减小,面团的粘弹性和结构强度增加;水分分布得到改善,弱结合水的流动性提高,强结合水的含量增加;二级结构中的β-折叠和无规则卷曲的相对含量显著降低（P<0.05）,而β-转角则显著增加（P<0.05）,减弱了麦麸对面筋蛋白的解聚作用。与此同时,发酵麦麸显著降低（P<0.05）全麦面条的蒸煮损失率。发酵麦麸组全麦面条的硬度和咀嚼度减小,弹性和粘聚性有所增加。消化实验表明发酵麦麸面条的葡萄糖释放量均低于普通小麦粉面条以及未发酵麦麸面条,强化了全麦面条淀粉的抗消化性。     

The effects of cereal additives in low-fat sausages and meatballs. Part 1: Untreated and enzyme-treated rye bran

Rye bran was added to frankfurter-type sausages and meatballs with the aim of producing low-fat products with increased dietary fibre content. The addition of untreated rye bran to sausages was detrimental, causing a substantial increase in frying loss (20% compared to 13.2%). The addition of rye bran treated with hydrolytic enzymes reduced the frying loss to 15.2–16.4%. The firmness was also improved by the treatments (12.8–14.2 N compared to 8.8 N). Enzymatic treatment of rye bran did not however improve the water-holding capacity or the texture of sausages compared to the rye bran that had only been soaked in water. The reason could be that enzymes degraded the solubilized fraction of the dietary fibre, leaving small fragments that cannot contribute to the water-holding capacity and the texture of the sausages. The benefits of treating rye bran in water were not seen in meatballs, probably due to the more particulate structure of meatballs, which is not as sensitive to additives.     

Effects of alkaline,hydrogen peroxide-treated fibres on nutrient digestibility,blood sugar and lipid profile in rats

Three diets containing different sources of dietary fibre, wheat bran, faba bean testas and rice hulls, were tested to determine the effects of alkaline, hydrogen peroxide (AHP)-treated fibre at 10% substitution level of dextrose corn flour on apparent digestibility, faecal characteristics, and levels of plasma glucose and lipid profile in rats. A fourth non-fibrous diet was used as a control. The results showed that, although AHP treatment of fibres resulted in reduction of their weight after washing, it caused an increase in their water absorption and in their swollen volume when mixed with an excess of water (up to three fold) as in the case of wheat bran. Rats consuming diets containing dietary fibres showed a significant loss of body weight but no significant effects on heart weight or liver weight were found. Faeces of rats fed on dietary fibre diets showed an increase in weight and volume, which resulted in reduction of faecal density. The consumption of the treated fibre significantly reduced total cholesterol, plasma triglycerides and blood sugar; wheat bran was the most effective followed by rice hulls and faba bean testas. On the other hand, it effected an increase in the plasma content of high-density lipoprotein HDL-C but this increase was only significant in rats fed with wheat bran. Alkaline hydrogen peroxide-treated fibres showed a great improvement in their absorbency, making them equal to or even better than untreated fibre in lowering blood lipids and sugar levels, in addition to their excellent effect on the physiological function of the intestinal tract.