Preparation and characterisation of dietary fibre from sugar beet pulp

Dried sugar beet pulp was ground and washed with 95% ethanol in order to obtain a colourless and odourless product which could be used as dietary fibre after drying and sieving. Sugar beet fibre had the same chemical composition as the initial pulp: 26–32% of hemicelluloses, 22–24% cellulose, 21.5–23% uronic acids, ～1–2% lignin, ～7–8% protein, 7.5–12% ash and ～0.5% residual sucrose. The main physicochemical properties such as density, cation exchange capacity (～0.6 meq g^?1) and water holding capacity (24–32 g g^?1) were determined. The water holding capacity of sugar beet fibre was only slightly affected by pH and ionic strength (adjusted by NaCl or CaCl₂) but it held less water in the H⁺ form than in the salt form, Na⁺ or Ca²⁺.     

Biochemical parameters of rats fed dietary fibre preparation from sugar beet

Groups of 15 male rats were fed ad libitum for 4 weeks with a standard diet containing 0, 2.5, 5.0 or 10.0% dietary fibre (DF) prepared from sugar beet. The highest food consumption was found in the group with 10% DF in the diet. Food efficiency was highest in the control group. Average body weight increased continuously in all groups without significant differences. Enrichment of the diet with the DF preparation did not substantially influence urinary parameters [pH, specific gravity, protein or activities of aspartate aminotransferase (ASAT), alanine aminopeptidase and alkaline phosphatase (AP)]. Haemoglobin concentration and haematocrit, mean corpuscular haemoglobin concentration and mean corpuscular volume as well as total numbers of erythrocytes, thrombocytes and leukocytes counts did not significantly differ between the groups. Lower counts of eosinophils and neutrophils were measured in rats fed DF-enriched diets. Serum parameters (urea-N, protein, glucose, triglycerides and activities of ASAT, alanine aminotransferase, AP and leucine aminopeptidase) did not differ between groups. As the amount of DF preparation in the diet increased, serum cholesterol was reduced in trend. Furthermore, no significant differences were found between the groups with respect to the organ weights of rats. In conclusion, important or critical dose-related differences in the determined parameters were not found. This sub-acute feeding study showed that no toxic effects were related to used doses of DF which was prepared from sugar beet.     

Simplified methods for the preparation and analysis of dietary fibre

A critical study was made of the various factors which affect the quantitative removal of starch, by enzymic methods, from starch-rich products; the products examined include potatoes, potato powder, oats and rye biscuit. Disruption of product by ball-milling in aqueous ethanol, followed by gelatinisation, are essential to give maximum enzyme accessibility as shown by light microscopy and analytical studies. The enzyme preparations were checked for the presence of contaminating β-glucanase activity using suitable substrates. The recommended method for the removal of starch involves treatment with either a mixture of human salivary α-amylase and pullulanase or amyloglucosidase; the first method was found to be slightly better. Based on these studies simplified methods for the preparation of dietary fibre (DF) have been formulated. The neutral sugars released from the DF on 1m H₂SO₄- or Saeman-hydrolysis were estimated by the alditol acetate procedure, and a modified carbazole method has been used for the estimation of total uronic acid in the fibre. A set of determinations which gives an estimate of the main types of DF polymers, including the enzymically non-degradable starch of processed products, is given. Although the method is not suitable for preparing gram-quantities of relatively pure DF, it can be used for screening a range of products. Some of the problems associated with the use of Van Soest neutral detergent fibre for estimating DF content of food products are also described.     

Date flesh: Chemical composition and characteristics of the dietary fibre

The date by-products of two date palm (Phoenix dactylifera L.) cultivars, Deglet-Nour and Allig, from the Degach region (Tunisia), were analysed for their main chemical composition. Studies were also conducted on the physicochemical properties (colour, water and oil-holding capacity and rheological behaviour) of dietary fibre (DF) extracted from date flesh. The following values (on a dry matter basis: DM) were obtained for fleshes of Deglet-Nour and Allig cultivars, respectively: sucrose 52.7% and 13.9%, glucose 13.7% and 29.9%, fructose 12.6% and 29.0%, total dietary fibre 14.4% and 18.4%, protein 2.1% and 3%, ash 2.5% and 2.52%. Insoluble DF, the major fraction of total DF, constituted 9.19–11.7% DM for Deglet-Nour and Allig, respectively. The elaboration of DF concentrates from date fleshes was characterised by an extraction yield of 67%. The chemical composition of these DF concentrates showed high total DF contents (between 88% and 92.4% DM) and low protein and ash contents (8.98–9.12% and 2.0–2.1% DM, respectively). The DF concentrates showed a high water-holding capacity (∼15.5 g water/g sample) and oil-holding capacity (∼9.7 g oil/g sample) and pseudoplasticity behaviour of their suspensions. Thus, date DF concentrates may not only be an excellent source of DF but an ingredient for the food industry.     

Chemical composition and physical properties of modified dietary fibre sources

The influence of thermal treatments on the chemical composition and the physical properties of yellow pea hulls, apple pomace and depectinised apple pomace were determined. The chemical composition of yellow pea hulls and apple pomace was altered only slightly. With depectinised apple pomace, however, the heat treatments led to a significant loss of the total dietary fibre (TDF) content. Water uptake, water binding capacity, rheological behaviour in the farinograph and oil absorption were determined before and after boiling, autoclaving and extrusion cooking. The physical properties of all samples were considerably affected by the thermal modifications. Whilst in cooked dietary fibre samples the water uptake, the water binding capacity and the oil absorption was always enhanced, the influence of autoclaving and extrusion cooking on the physical properties depended very much on the dietary fibre source. Yellow pea hulls showed unchanged or slightly increased values, while the results for the two apple pomace preparations were lower compared with the untreated samples. The differences in the farinogramsiwere less obvious since the dietary fibre content in the dough mixtures was only in the range of 10–20%.     

Effect of processing on the composition of dietary fibre and starch in some legumes

The effect of processing on the total dietary fibre (TDF) insoluble (IDF) and water-soluble (SDF) fractions as well as total (TS), available (AS) and resistant (RS) starch were studied in three legumes, viz. bengalgram (Cicer arietinum L.), Cowpea (Vigna unguiculata) and greengram (Vigna radiata). The processes studied were fermentation, germination, pressure-cooking and roasting. The dietary fibre (DF) content and its components were determined using the enzymatic-gravimetric method. The TS content was determined by the enzymatic method after solubilization with KOH. The DF content ranged from 23.2 to 25.6 g/100 g in the raw and 16.0 to 31.5 g/100 g in the processed legumes. All the processing treatments significantly decreased the SDF content and increased the IDF content of all the three legumes. The mean TS, AS and RS content of the raw legumes were similar, 46.9, 36.7 and 10.2 g/100 g respectively. AS content of all the legumes was reduced by the processing treatments, except pressure cooking. Correspondingly, higher amounts of RS were observed in the processed legumes, except pressure cooked, resulting in an increase in the TDF content.     

Laminarin in the dietary fibre concept

Dietary fibres consist of edible plant polysaccharides that are resistant to digestion and absorption in the human small intestine but undergo complete or partial fermentation in the colon. Seaweeds, notably Laminaria spp, are particularly rich in polysaccharides resistant to hydrolysis in the upper gastrointestinal tract and are, in consequence, considered as dietary fibres. Most of the carbohydrates from Laminaria spp are thought to be indigestible by humans. The main storage polysaccharide of these algae is laminarin, a β‐polymer of glucose. The aims of this work were, on the one hand, to compare various methods of extraction of laminarin by partial characterisation of the product obtained and, on the other hand, to study the fate of this polysaccharide and its effects in the gastrointestinal tract in order to determine its potential as a dietary fibre in human nutrition. Among four methods tested to extract laminarin, the best appeared to be a hot HCl‐based method. Human digestive enzymes did not hydrolyse laminarin, so this polysaccharide can be considered as a dietary fibre. After ingestion by rats, this polysaccharide was not found in faeces of these animals. It did not increase the intestinal transit and stool output in vivo, but it increased the contractile response of the stomach to acetylcholine in vitro. Copyright © 2004 Society of Chemical Industry     

Possible effects of dietary polyphenols on sugar absorption and digestion

Excessive post‐prandial glucose excursions are a risk factor for developing diabetes, associated with impaired glucose tolerance. One way to limit the excursion is to inhibit the activity of digestive enzymes for glucose production and of the transporters responsible for glucose absorption. Flavonols, theaflavins, gallate esters, 5‐caffeoylqunic acid and proanthocyanidins inhibit α‐amylase activity. Anthocyanidins and catechin oxidation products, such as theaflavins and theasinsensins, inhibit maltase; sucrase is less strongly inhibited but anthocyanidins seem somewhat effective. Lactase is inhibited by green tea catechins. Once produced in the gut by digestion, glucose is absorbed by SGLT1 and GLUT2 transporters, inhibited by flavonols and flavonol glycosides, phlorizin and green tea catechins. These in vitro data are supported by oral glucose tolerance tests on animals, and by a limited number of human intervention studies on polyphenol‐rich foods. Acarbose is a drug whose mechanism of action is only through inhibition of α‐amylases and α‐glucosidases, and in intervention studies gives a 6% reduction in diabetes risk over 3 years. A lifetime intake of dietary polyphenols, assuming the same mechanism, has therefore a comparable potential to reduce diabetes risk, but more in vivo studies are required to fully test the effect of modulating post‐prandial blood glucose in humans.     

功能性强化大豆膳食纤维的生理功效及其在食品上的应用

叙述了功能性强化大豆膳食纤维的物化特性、生理功效及其在食品上的应用。大豆膳食纤维不能为人体提供任何营养物质,但对人体具有多种重要的生理活性作用。改性纤维在保留膳食纤维的全部性质和生理作用的基础上,增加了更多的功能,应用范围进一步拓展,在食品、医药等行业有着更为重要的应用价值。      

利用蔗渣制备膳食纤维的研究

<正> 膳食纤维因其重要的生理特性而迅速成为国内外新兴的功能性食品,在膳食中增加纤维摄入量成了西方国家为防治“文明病”的一种方法。我同人民由于膳食不平衡或营养吸收过剩,文明病早已出现,这种情况在经济比较发达的沿海地区尤显严重。因此,升展膳食纤维的研究对提高我国人民健康状况极具意义。自然界中富含纤维的原料很多,国外研究过的包括谷物纤维、果蔬纤维、豆类纤维、微生物纤维、其它天然纤维和合成半合成纤维共6大类30余种,其中应用在实际生产的不超过10种。目前国内的研究重点集中在小麦纤维、大豆纤维与     

Development of a method to measure dietary fibre in oranges

A method to measure dietary fibre in oranges has been developed. Pectin was extracted from the food sample using heat, acid and a cation-exchange resin. This was followed by enzymic digestions, using pepsin and pancreatin, of the remaining residue. Optimal levels of resin, pH, time and temperature for maximum pectin extraction were found. Optimal levels of enzymes and pH for maximal enzyme digestion was also found. Other food products tested for dietary fibre content were: cauliflower, oranges, pole beans, carrots and whole wheat flour. Values found were greater than those for other fibre analyses; however, most other methods fail to measure the water-soluble indigestible components, such as pectin.     

Body composition, dietary carbohydrates and fatty acids determine post-fertilisation development of bovine oocytes in vitro

This study assessed the interactive effects of carbohydrate type (fibre vs starch) and fatty acid (FA) supplementation (0% vs 6% calcium soaps of palm oil FA) on the post-fertilisation development of oocytes recovered from low and moderate body condition score (BCS) heifers. A secondary objective was to compare the FA composition of plasma to that of granulosa cells (GCs) and cumulus-oocyte complexes (COCs) from these animals, and to relate these findings to the developmental potential of oocytes. Plasma, GCs and COCs were recovered from 32 heifers on day 5 of a synchronised oestrous cycle for FA analyses. Oocytes were also recovered on days 10 and 15 of the same cycle after short-term ovarian stimulation (FSH + GnRH), and matured, fertilised and cultured to the blastocyst stage in vitro. High levels of dietary starch increased (P < 0.01) plasma insulin but, together with dietary FA, reduced (P < 0.05) blastocyst yields in low, but not in moderate, BCS heifers. Diet-induced alterations to the FA content of plasma were less apparent in GCs and COCs. In summary, although dietary lipids increased the FA content of COCs, the selective uptake of saturated FAs at the expense of mainly polyunsaturated FAs within the follicular compartment ensured that the FA composition of COCs was largely unaffected by diet. However, the concentration of saturated FAs within COCs was inherently high, and so further increases in FA content may have impaired post-fertilisation development. The data establish a robust nutritional framework for more detailed studies into the mechanistic effects of dietary composition on the post-fertilisation developmental potential of oocytes.     

Evaluation of methods of analysis for dietary fibre using real foods and model foods

Rationale and objectives

There are several rational and empirical methods for the measurement of dietary fibre and its components. A selection of these methods were evaluated by investigation of a range of real foods and model foods with added resistant starch (RS), non-starch polysaccharides (NSP) and resistant oligosaccharide (RO) ingredients.

Methods

A range of rational methods were applied in determining specific carbohydrate constituents: RS, NSP and RO, including fructans. For comparison, empirical methods AOAC 991.43 (2001.03) and AOAC 2009.01 were applied, based on determination of gravimetric residues for high molecular weight and size-exclusion HPLC analysis of the ethanol filtrate for low molecular weight components.

Results

In general there was agreement between different rational methods for the analysis of RS and fructans, though there were notable exceptions for some product types. Comparison of methods for total RS and those that only measure the RS3 fraction, from retrograded starch, indicated that RS3 was the only type present for most processed products. This also explains the similar results obtained by AOAC 991.43 (2001.03) and AOAC 2009.01, though the latter is intended to recover other RS types as well. For many products there was agreement between results obtained by rational and empirical methods, though there were exceptions and the reasons for these are discussed.

Conclusion

Rational and empirical methods can both be used to determine dietary fibre in most situations. The information provided by rational methods is useful in identifying the specific carbohydrate constituents present in foods and can assist in determining whether added extracted and synthesised ingredients are ones that conform to the Codex and EU dietary fibre definition.     

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.     

Composition of dietary fibre in cocoa husk

 This paper describes the total non-starch polysaccharide (NSP), soluble and insoluble dietary fibre (SDF and IDF) content of processed cocoa husk (cocoa butter <3 g/100 g) determined according to Englyst's enzymatic-chemical procedure. In addition, fibre values were determined by measuring the levels of the composite sugars by spectrophotometry and gas chromatography methods, and the fractions acid-detergent fibre, neutral-detergent fibre, crude fibre, Klason lignin, starch, crude protein, ash, fat, water content, and water-holding capacity (WHC). The NSP content was 43.8±2.32 g/100 g (28.34 g/100 g IDF plus 15.60 g/100 g SDF), the mean soluble fibre concentration was 35.5% of total fibre. Klason lignin content, estimated gravimetrically, was 13.7±1.8 g/100 g. Cellulose (19.7±1.48 g/100 g) and uronic acids (12.4±1.35 g/100 g) were the main type of IDF and SDF substances, respectively. The analysis of neutral sugar constituents showed the presence of glucose, the predominant sugar, followed by arabinose, galactose and xylose. The WHC was 3.62±0.47 g water/g cocoa husk. Received: 19 December 1997 / Revised version: 27 February 1998     

Sources of error in dietary fibre analysis

The following error sources in the present dietary fibre (DF) analytical methods were investigated: (1) the omission of the protease treatment of samples may modify the results by increasing the Klason lignin fraction and altering the content and/or distribution of polysaccharides; (2) some soluble dietary fibre (SDF) constituents can be retained in the insoluble dietary fibre (IDF) matrix affecting the insoluble and soluble fraction distribution; (3) protein, ash and blank corrections in gravimetric analysis involve a lack of precision, over- or undervaluing the actual DF contents; (4) the Klason lignin fractions obtained by acid hydrolysis of DF residues are made up of different components and artifacts besides lignin.

These studies included both new observations and additional quantitative evidence on error sources previously mentioned in the literature. In some cases the published methods were modified to emphasize the methodological errors.     

Composition of dietary fibre in cocoa husk

 This paper describes the total non-starch polysaccharide (NSP), soluble and insoluble dietary fibre (SDF and IDF) content of processed cocoa husk (cocoa butter <3 g/100 g) determined according to Englyst's enzymatic-chemical procedure. In addition, fibre values were determined by measuring the levels of the composite sugars by spectrophotometry and gas chromatography methods, and the fractions acid-detergent fibre, neutral-detergent fibre, crude fibre, Klason lignin, starch, crude protein, ash, fat, water content, and water-holding capacity (WHC). The NSP content was 43.8±2.32 g/100 g (28.34 g/100 g IDF plus 15.60 g/100 g SDF), the mean soluble fibre concentration was 35.5% of total fibre. Klason lignin content, estimated gravimetrically, was 13.7±1.8 g/100 g. Cellulose (19.7±1.48 g/100 g) and uronic acids (12.4±1.35 g/100 g) were the main type of IDF and SDF substances, respectively. The analysis of neutral sugar constituents showed the presence of glucose, the predominant sugar, followed by arabinose, galactose and xylose. The WHC was 3.62±0.47 g water/g cocoa husk. Received: 19 December 1997 / Revised version: 27 February 1998