Diferulates as structural components in soluble and insoluble cereal dietary fibre

Cell wall cross‐linking can have a substantial effect on the properties of the wall. To estimate cross‐linking (between arabinoxylans) in cereal fibres, dehydrodiferulate levels were measured in soluble and insoluble dietary fibre (SDF and IDF) isolated from whole grains of maize (Zea mays L), wheat (Triticum aestivum L), spelt (Triticum spelta L), rice (Oryza sativa L), wild rice (Zizania aquatica L), barley (Hordeum vulgare L), rye (Secale cereale L), oat (Avena sativa L) and millet (Panicum miliaceum L). After saponification of the cereal fibres the extracts were investigated for dehydrodimers of ferulic acid using GLC–MS and GLC–FID. From most cereal IDF the whole spectrum of dehydrodiferulic acids (DFAs) (8‐5′‐, 8‐8′‐, 5‐5′‐, 8‐O‐4′‐ and 4‐O‐5′‐coupled) could be identified. The absolute contents of total DFAs ranged between 2.4 and 12.6 mg g^?1. With the exception of 4‐O‐5′‐coupled DFA, the whole range of DFAs was also detected from cereal SDF but only in amounts of 40–230 µg g^?1. It was estimated that arabinoxylans of cereal IDF contain 8–39 times more diferulates than arabinoxylans of cereal SDF (where measurement of DFA levels in SDF was possible). In cereal IDF, 8‐5′‐coupled dimers dominated, whereas in cereal SDF, 8‐8′‐coupled dimers were relatively enhanced and often became the major dimers. © 2001 Society of Chemical Industry     

酶解法改善不溶性大豆膳食纤维持水力的研究

采用酶解法对来源于大豆的不溶性膳食纤维（IDF）进行生物改性处理,以提高其持水力和膨胀力。探讨了改性过程中溶液pH、酶用量、温度以及时间对改性的影响。特别比较了木聚糖酶、β-葡聚糖酶、纤维素酶和半纤维素酶的改性效果,确定木聚糖酶对提高IDF持水力的效果最明显。通过正交实验得出木聚糖酶改性的最佳工艺条件为：pH5．0,酶用量0．1mL,于60℃水浴中酶解60min。在此条件下经过改性的IDF持水力可达13．95g／g,膨胀力为18．45mL/g,吸油力为7．15g／g,分别比原料提高了49．36％、28．66％和60．67％。     

Water‐holding capacity of insoluble fibre decreases free water and elevates digesta viscosity in the rat

BACKGROUND: The relationships between possible physiological properties of insoluble fibre and the viscosity of digesta are poorly understood. The aim of this study was to investigate the effect of insoluble fibres with different water‐holding capacity, swelling, oil‐holding capacity and cation exchange capacity on gastric, small intestinal and caecal contents in rats fed a semi‐purified diet containing either no fibre (control), 50 g kg^?1 tossa jute fibre or 50 g kg^?1 shiitake fibre. RESULTS: The water‐holding capacity, swelling, oil‐holding capacity and cation exchange capacity of insoluble fibres of tossa jute were higher than those of shiitake (P < 0.001). The order of the viscosities of digesta was control group < shiitake fibre group < tossa jute fibre group in gastric, small intestinal and caecal contents (P < 0.05). The digesta viscosity at a shear rate of 40 s^?1 was strongly correlated with the free water content of digesta (r = ? 0.89; P < 0.01). The free water content of digesta depended on the water‐holding capacity of insoluble fibres represented as a linear function with negative slope (P < 0.001). CONCLUSION: The viscosity of digesta depends on the free water content, and this is reduced by fibre that holds water and can swell. Copyright © 2008 Society of Chemical Industry     

Gravimetric method for the determination of insoluble and soluble dietary fibres

The present paper describes a simple method for the determination of the insoluble and soluble dietary fibres in food. In a first step, starch and proteins are removed by enzyme treatment. The insoluble dietary fibres are determined gravimetrically after centrifugation and washing of the residue with water, ethanol, acetone and diethyl ether. The water-soluble dietary fibres are recovered from the supernatant liquid of the centrifugation by dialysis, freeze-drying, and subsequent weighing. The method has been used for the determination of dietary fibres in by-products from the industry.     

Gravimetric method for the determination of insoluble and soluble dietary fibres

The present paper describes a simple method for the determination of the insoluble and soluble dietary fibres in food. In a first step, starch and proteins are removed by enzyme treatment. The insoluble dietary fibres are determined gravimetrically after centrifugation and washing of the residue with water, ethanol, acetone and diethyl ether. The water-soluble dietary fibres are recovered from the supernatant liquid of the centrifugation by dialysis, freeze-drying, and subsequent weighing. The method has been used for the determination of dietary fibres in by-products from the industry.

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Gravimetrische Bestimmung der unlöslichen und löslichen Nahrungsfasern

Zusammenfassung Die vorliegende Arbeit beschreibt eine einfache Methode zur Erfassung löslicher und unlöslicher Nahrungsfasern in Lebensmitteln. Zunächst werden Stärke und Proteine enzymatisch abgebaut. Die unlöslichen Nahrungsfasern werden nach Zentrifugation, Waschen des Rückstandes mit Wasser, Ethanol; Aceton und Diethylether und Trocknen zur Gewichtskonstanz gravimetrisch bestimmt. Die im Überstand der Zentrifugation sich befindenden löslichen Nahrungsfasern werden dialysiert, gefriergetrocknet und dann gewogen. Die Methode wurde an verschiedenen nahrungsfaserreichen Nebenprodukten der Lebensmittelindustrie angewendet.

     

Characterisation of alkaline and enzymatic modified insoluble dietary fibre from Undaria pinnatifida

Undaria pinnatifida insoluble dietary fibre (UIDF) was modified by alkali (NaOH solution) and complex enzyme (xylanase and cellulase) to improve the physicochemical properties. Scanning electron microscopy revealed that the surface structure after modification was rough and loose. The characteristic absorption peaks in Fourier transfer infrared spectrometry and X-ray diffraction patterns showed that enzymes can further hydrolyse the UIDF than alkali mainly in amorphous region, and increased the soluble dietary fibre content to 16.31%. The alkaline and complex enzymatic modification both resulted in higher water retention capacity, water swelling capacity, oil absorption capacity, glucose adsorption capacity and the inhibition ability towards α-amylase. The complex enzymatic modification exhibited better features in almost all properties, and the modification did not change the inhibiting mechanism on α-amylase (non-competitive type). Overall, both two modifications could effectively improve the properties of UIDF, which may promote its use in food applications.     

Dependence of the effective diffusion coefficient of moisture with thickness and temperature in convective drying of sliced materials. A study on slices of banana, cassava and pumpkin

Several studies have indicated that effective diffusion coefficients of slices apparently vary with the thickness of the samples. Even though the effective diffusion coefficients have been observed to be dependent on the square of the slice thickness, a theoretical explanation to this behavior is not available to date. A theoretical model is formulated herein, in order to correlate effective diffusion coefficient of moisture in the slices with the slice thickness. Experiments are carried out for drying of slices of different thicknesses of banana, cassava and pumpkin in order to evaluate the effective diffusion coefficients. The model is found to describe the variation of the effective diffusion coefficient with slice thickness very satisfactorily. A possibility of the estimation of the axial and radial diffusion coefficients of moisture in the slices is also outlined.     

Methods for determination of insoluble and soluble dietary fiber in food stuff

A comparative evaluation of two enzymatic methods (method after Asp and the Berlin Method) and a detergent method (modified NDF-Method) for the determination of dietary fiber in food was carried out. The procedure of the Berlin Method is described in detail. The methods were used to analyse the dietary fiber content of cereal-based samples. In comparison with the other methods, the NDF-Method consistently gave lower dietary fiber values. This was also the case when only the insoluble dietary fiber was determined. With the enzymatic methods, the method after Asp gives higher values for the insoluble and lower values for the soluble dietary fiber than the Berlin Method.     

The phenolic composition and antioxidant capacity of soluble and bound extracts in selected dietary spices and medicinal herbs

Phenolic compounds, commonly found in plant‐based foods, exist in free or bound form. Despite much research on the soluble phenolics in spices and herbs, their bound phenolics have not been intensively investigated. In this study, six common dietary spices and medicinal herbs (Padang cassia, oregano, clove, Chinese cassia, Japanese knotweed and peel of pomegranate) were selected to evaluate and compare their phenolic composition and antioxidant capacity in soluble extracts (SEs) and bound extracts (BEs). Generally, the samples had high total phenolic content and antioxidant capacity, with lower levels in the BEs. From the HPLC results, (+)‐catechin, (?)‐epicatechin, eugenol, cinnamaldehyde and carvacrol were the major phenolic compounds in the SEs, and gallic acid, p‐coumaric acid and ellagic acid in the BEs. Phenolic compounds are likely the major contributors to the antioxidant capacity of these plant samples. Overall, these dietary spices and medicinal herbs can be excellent sources of natural antioxidant phenolics.     

油橄榄果渣水不溶性膳食纤维结构表征及体外吸附性能研究

以油橄榄脱脂果渣为原料,采用碱法制备油橄榄果渣水不溶性膳食纤维（Insoluble dietary fiber,IDF）,并用红外光谱和X射线衍射等方法对其表征,并测定分析其体外吸附NO-2和重金属Pb²⁺、Cu²⁺、Cd²⁺的功能特性。结果表明:油橄榄果渣IDF中水不溶性膳食纤维含量为90.09%,其主要由纤维素、半纤维素和木质素组成;红外光谱图显示油橄榄果渣IDF具有糖类和木质素的特征吸收峰;X射线衍射图显示油橄榄果渣IDF呈纤维素I晶型,其结晶度为47.94%;在体外模拟胃环境（pH2）下,油橄榄果渣IDF对NO₂^-的吸附在240 min时达到平衡,平衡吸附量为826μg/g;在体外模拟肠道环境（pH7）下,油橄榄果渣IDF对Pb²⁺、Cu²⁺、Cd²⁺的平衡吸附量分别为418.7、686.6、849.5μg/g,IDF在肠道环境下对Pb²⁺、Cu²⁺、Cd²⁺的吸附能力均优于胃环境。IDF对Pb²⁺、Cu²⁺、Cd²⁺的吸附过程符合准二级动力学方程。      

添加油脂对重组肉干硬度和持水性的影响

采用重组成型的方法制作中式肉干产品,研究不同油脂添加量(0%、3%、6%、9%和12%)对重组肉干产品硬度的影响,并拟合不同样品的解析等温线,分析添加油脂对产品持水性的影响。结果表明,样品在55℃干燥24 h时,添加的油脂能够阻碍水分的扩散,从而提高产品的含水量,降低产品的硬度值;同时通过对六种常用模型的非线性拟合,得出GAB模型获得了重组肉干产品的解析等温线;该等温线表明,恒定某一aW,随着油脂添加量的增加,产品的干基含水量先降低后增加,说明油脂的增加有促进水分游离的作用,而高油脂的添加可能会通过油膜层的形成来减少水分的挥发。      

不同溶解性膳食纤维的功能特性差异浅析 及其在肉制品中应用

膳食纤维是一种植物成分,在消化过程中胃中的酶不能将其分解,是人类所需的第七大营养素。膳食纤维按其溶解性可分为可溶性和不溶性膳食纤维两大类,而且不同溶解性膳食纤维功能特性方面有很大差异,一般可溶性膳食纤维形成溶胶或凝胶,有很强的吸附性和清除能力,一般研究水溶性膳食纤维的对胆酸、胆固醇及有害物质的吸附性能,以及清除自由基的能力。不溶性膳食纤维主要研究粒径、温度等因素,对膳食纤维的膨胀力、持水力、吸油力和结合水力的影响。可溶性与不溶性膳食纤维的制备工艺方法存在差异,得率因品种不同有较大差异,持水力、溶胀率等理化特性也差异很大。本文还介绍了国内外将多种不同类型和来源的膳食纤维添加在肉制品(香肠、火腿、重组肉制品、凝胶肉制品、汉堡等)中的应用研究进展。目前对于不同溶解性膳食纤维的性质还没有确切科学的结论。如果能将不同膳食纤维本身的性质研究透彻,确定什么理化特性或结构特征赋予了膳食纤维在不同功能食品中的各种功能特性,将使商业与研究如何选择和制备合适品种的膳食纤维提供科学依据。     

Impact of cell wall‐degrading enzymes on water‐holding capacity and solubility of dietary fibre in rye and wheat bran

BACKGROUND: Rye and wheat bran were treated with several xylanases and endoglucanases, and the effects on physicochemical properties such as solubility, viscosity, water‐holding capacity and particle size as well as the chemical composition of the soluble and insoluble fractions of the bran were studied. A large number of enzymes with well‐defined activities were used. This enabled a comparison between enzymes of different origins and with different activities as well as a comparison between the effects of the enzymes on rye and wheat bran. RESULTS: The xylanases derived from Bacillus subtilis were the most effective in solubilising dietary fibre from wheat and rye bran. There was a tendency for a higher degree of degradation of the soluble or solubilised dietary fibre in rye bran than in wheat bran when treated with most of the enzymes. CONCLUSION: None of the enzymes increased the water‐holding capacity of the bran or the viscosity of the aqueous phase. The content of insoluble material decreased as the dietary fibre was solubilised by the enzymes. The amount of material that may form a network to retain water in the system was thereby decreased. © 2012 Society of Chemical Industry     

Effect of dietary fibre enrichment on selected properties of gluten-free bread

The enrichment of gluten-free baked products with dietary fibre seems to be necessary since it has been reported that coeliac patients have generally a low intake of fibre due to their gluten-free diet. In the present study different cereal fibres (wheat, maize, oat and barley) were added at 3, 6 and 9 g/100 g level into a gluten-free bread formulation based on corn starch, rice flour and hydroxypropyl methyl cellulose (HPMC). Doughs were evaluated based on consistency, viscosity and thermal properties. Results showed that maize and oat fibre can be added to gluten-free bread with positive impact on bread nutritional and sensory properties. All breads with 9 g/100 g fibre increased the fibre content of control by 218%, but they were rated lower than those with 3 and 6 g/100 g fibre due to their powdery taste. The formulation containing barley fibre produced loaves that had more intense color and volume comparable to the control. During storage of breads a reduction in crumb moisture content and an increase in firmness were observed. The micrographs of the crumb showed the continuous matrix between starch and maize and/or oat fibre obtaining a more aerated structure.     

超声波处理对水不溶性膳食纤维膨胀力及持水力的影响

采用超声波法对马铃薯渣中的水不溶性膳食纤维(PIDF)进行处理,研究超声功率、超声时间、超声温度及料液比对水不溶性膳食纤维基本性质的影响。通过单因素和正交实验,确定最佳处理条件:膨胀力的最佳工艺条件为料液比1∶10,超声时间50min,超声温度70℃,超声功率70W,膨胀力为20.50mL/g;持水力的最佳工艺条件为料液比1∶15,超声时间40min,超声温度80℃,超声功率70W,持水力为14.81g/g。      

Plasma lipid regulatory effect of compounded freshwater clam hydrolysate and Gracilaria insoluble dietary fibre

This study investigates the hypocholesterolemic effects of a diet containing freshwater clam hydrolysate (PX) and insoluble dietary fibre from whole Gracilaria (IDF). Freshwater clam meat and whole dried Gracilaria were separately extracted using hot water. The residual meat was hydrolysed at 50 °C by Protamex to obtain freshwater clam hydrolysate (PX). Levels of triacylglycerol and cholesterol in Sprague–Dawley (SD) rats were compared with those of rats fed diets containing casein and cellulose as a control. Plasma triacylglycerol levels decreased by 65.8%, 27.9%, and 44.3%, respectively, in PX10 (16.6% hydrolysate), IDF10 (13.0% IDF) and compounded PX10/IDF10 groups, while plasma total cholesterol levels decreased by 26.1%, 24.2%, and 17.1%, respectively. In the liver, triacylglycerol levels decreased by 27.6%, 21.0%, and 28.0%, respectively, while total cholesterol levels decreased by 50.0%, 38.5%, and 48.6%, respectively. The compound PX10/IDF10 diet group showed a higher excretion of faecal total cholesterol and bile acids levels than did the other groups.     

花生麸水溶性膳食纤维提取工艺的研究

采用正交实验探讨了花生麸水溶性膳食纤维的最佳提取工艺 ,得到最佳工艺条件为 :水浴温度 T=10 0℃ ,p H=7,时间 t=15 min,提取液用量为 5 m L· g- 1 ,在此条件下的提取率为 7.0 4 %。     

Investigation of the interaction between soluble antioxidants in green tea and insoluble dietary fiber bound antioxidants

This work investigates the possibility of interaction between insoluble dietary fiber bound antioxidants, specifically of wheat bran, and soluble antioxidants like those provide by aqueous infusions of green tea. Solutions of pure catechins were also assayed for comparison with those naturally found in tea. To accomplish this, the aqueous and alcohol soluble fractions as well as the lipid components of wheat bran were firstly removed and the freeze-dried insoluble residue was then treated with different concentrations of green tea infusions or aqueous solutions of epicatechin (EC) and epigallocatechin-3-gallate (EGCG) for certain time. Treatment with EC (0–200 μM) had no significant effect on the antioxidant capacity of insoluble bran fraction. However, treatment with EGCG significantly (p < 0.05) increased linearly the antioxidant capacity as a function of concentration (0–100 μM). Treatment with great tea infusions (1–3 g/100 ml) also increased the resulting antioxidant capacity of insoluble bran fraction, but the effect was lesser at higher infusion concentrations. Liquid chromatography couple to mass spectrometry (LC–MS) analyses of aqueous phases after treatment indicated comparable levels of decrease in the concentrations of catechins confirming their reaction with the radical forms of antioxidants bound to insoluble bran matrix.     

Influence of germination on the soluble carbohydrates and dietary fibre fractions in non-conventional legumes

Influence of light exposure during germination on structural and soluble carbohydrates including total dietary fibre (TDF), insoluble dietary fibre (IDF) and soluble (SDF) dietary fibre fractions and also raffinose family oligosaccharides (RFOs) was studied in non-conventional legumes Vigna unguiculata (cowpea), Canavalia ensiformis (jack bean), Stizolobium niveum (mucuna), and Lablab purpureus (dolichos), and compared to a well known and used Glycine max (soybean). Non-conventional legumes were rich in DF, mainly IDF, which represented 93–97% of TDF. It was relevant the proportion of protein that remained associated to the insoluble DF matrix. Non-conventional legumes exhibited important levels of RFOs but their profile was different depending on the tropical seed. The germination of seeds produced changes in the carbohydrate fraction, mainly an increase of TDF in most instances, except for soybean, and a drastic reduction of RFOs, from 98% to 63%, with the corresponding increase in the amounts of total soluble sugars.