Non‐digestible carbohydrates in Brazilian soybean seeds [Glycine max (L.) Merril]

Non‐digestible carbohydrate fraction (NDCF) consists of a range of bioactive compounds that escape digestion in the small intestine. NDCF is mainly composed of dietary fibre (DF) and non‐digestible oligosaccharides (NDO). The objective of this work was to analyse directly and compare the NDCF in two Brazilian cultivars of soybean seed with commercial flour. Brazil is the second major soybean producer in the world. The seed cultivars showed on average a NDCF value of 32.80 g per 100 g dry weight (dw). Regarding DF, insoluble DF (IDF) was the main fraction amounting on average to 98%. Uronic acids were significantly higher than neutral sugar (NS) in IDF and soluble DF (SDF) fractions. There was a considerable amount of Klason lignin – on average 84.14% of DF. Regarding NS profile, mannose was the most important sugar in SDF, whereas galactose and arabinose were predominant in IDF. Stachyose was the main oligosaccharide in NDO. DF and NDO were in the same proportion (94.2:5.8) in tested cultivars. No differences in swelling, water retention, or oil retention capacities between seed cultivars were detected. This study on non‐digestible carbohydrate components in soybean seed gives a different approach to the current nutritional knowledge on protein and oil constituents.     

Characterisation of peach dietary fibre concentrate as a food ingredient

Insoluble and soluble dietary fibre (DF) fractions of peach DF concentrate, obtained by an enzymatic-chemical method, were analysed for neutral sugars, uronic acids and Klason lignin. Proximate composition, energy value, colour and water- and oil-holding capacities were also determined. Total DF constituted 31–36% dry matter (DM) of the concentrate and insoluble DF was its major fraction (20–24% DM). The high proportion of soluble fraction (11–12% DM) in the peach DF concentrate, in comparison with cereal brans, was noticeable. Insoluble and total dietary fibre contents significantly decreased throughout the harvest time of the original fresh fruit. Results suggested that peach DF concentrate may be not only an excellent DF source but an ingredient in the food industry because it showed a high affinity for water (9.12–12.09 g water/g fibre) and low energy (3.723–3.494 kcal/g). However, the use of this material could affect the colour and pH of the final product.     

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.     

Dietary fibre content and antioxidant activity of Manto Negro red grape (Vitis vinifera): pomace and stem

The general composition of two by-products of the vinification process of the Manto Negro red grape (Vitis vinifera) variety, namely pomace and stem, were determined. Both by-products present high contents of total dietary fibre (TDF), comprising three fourths of the total dry matter. The pomace had high protein (12.2%) and oil (13.5%) values and the stem large amounts of extractable polyphenols (11.6%). Due to the high fibre content, the soluble dietary fibre (SDF), insoluble dietary fibre (IDF), uronic acids (UA) and Klason lignin (KL) were analysed in both samples. Notable were the high percentage of soluble fibre (15%) in relation to the total dietary fibre for the pomace, as well as the high content of Klason lignin (KL) in both by-products, especially in the stem (31.6%). This fraction (KL) has important amounts of condensed tannins (CT) and resistant protein (RP).     

Roasting Effects on Dietary Fiber Composition of Cocoa Beans

The effect of roasting on dietary fiber fractions of cocoa beans was determined by gravimetric and fractionation procedures after enzymatic treatment. Roasting had no notable effect on total dietary fiber content (TDF). Components of insoluble dietary fiber (IDF) became redistributed after roasting. One of the largest changes was a sharp increase of Klason lignin. The noted decrease in sugar content without a change in IDF suggested that neutral sugars and uronic acids may be involved in Maillard polymer formation. Soluble dietary fiber (SDF) did not show large variations. Undigestible protein in IDF increased after roasting.     

Chemical composition of some forages and various residues from feeding value determinations

NDF, ADF, ‘cellulose’ and IVOMD residues, from feeding value determinations, were prepared from some forages, including straw, alkali-treated straw, grass and lucerne samples. The crude protein, cellulose, hemicellulose, uronic acid, Klason lignin, lignin and ash contents of these residues and the corresponding original forage samples were determined together with the relative composition of the neutral sugar constituents after acid hydrolysis. Cellulose, hemicellulose and Klason lignin were the main components in the NDF fractions but substantial amounts of crude protein (1–6%) also remained. Cellulose and Klason lignin were the main components in the ADF fractions, but 7–14% of the fractions was hemicellulose and 1–4% crude protein. Cellulose was the main component in the ‘cellulose’ fractions, but they also contained 8–13% hemicellulose, 2–7% Klason lignin and 2–11% ash. The composition of the IVOMD residues showed that cellulose and hemicellulose had been dissolved to about the same amounts (70–80%) and that most of the Klason lignin remained.     

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     

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     

Chemical composition of dietary fiber and polyphenols of five different varieties of wine grape pomace skins

The skins of two white wine grape pomace (WWGP) and three red wine grape pomace (RWGP) from US Pacific Northwest were analyzed for their dietary fiber (DF) and phenolic composition. DF was measured by gravimetric–enzymatic method with sugar profiling by HPLC–ELSD. Insoluble DF composed of Klason lignin (7.9–36.1% DM), neutral sugars (4.9–14.6% DM), and uronic acid (3.6–8.5% DM) weighed more than 95.5% of total DF in all five WGP varieties. WWGP was significantly lower in DF (17.3–28.0% DM) than those of RWGP (51.1–56.3%), but extremely higher in soluble sugar (55.8–77.5% DM vs. 1.3–1.7% DM) (p < 0.05). Soluble polyphenols were extracted by acidified 70% acetone and measured spectrophotometrically. Compared with WWGP, RWGP had higher values in total phenolic content (21.4–26.7 mg GAE/g DM vs. 11.6–15.8 mg GAE/g DM) and DPPH radical scavenging activity (32.2–40.2 mg AAE/g DM vs. 20.5–25.6 mg AAE/g DM) (p < 0.05). The total flavanol and proanthocyanidin contents were ranged from 31.0 to 61.2 mg CE/g DM and 8.0 to 24.1 mg/g DM, respectively for the five WGP varieties. This study demonstrated that the skins of WGP can be ideal sources of DF rich in bioactive compounds.     

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。      

Chemical composition of olive by-product and modifications through enzymatic treatments

The purpose of the present work was to study the dietary fibre (DF) fraction of olive cake and modify the fibre structure through enzymatic treatments in order to improve the sensory quality of this by-product for its incorporation into a baked product. Two different commercial enzyme preparations were used for enzymatic modifications: Viscozyme L, a hemecellulase/cellulase multi-enzyme complex, and Olivex which contains different pectolitic main activities as well as various side activities, hemicellulases and cellulases. DF consists of 800 g total dietary fibre per kg dry matter. More than 91% of the DF are insoluble and the monosaccharide composition of this fraction indicates the presence of mainly cellulose and xyloglucans or xylans. Approximately 75% of the uronic acids found in olive cake are associated to the insoluble DF (IDF). Arabinans and uronic acids polysaccharides are the major fibre components in the soluble DF (SDF) fraction. Enzymatic treatments with commercial preparations caused changes in the DF content and in the IDF:SDF ratio depending on enzyme concentrations and incubation time. Baking experiments showed that a substitution of 10% of wheat flour by enzymatically modified olive cake led to an improved texture compared to products containing untreated cake.     

Fractionation and characterization of ball‐milled and enzyme lignins from abaca fibre

An Erratum has been published for this article in Journal of the Science of Food and Agriculture 79(15) 1999, 2122. Ball‐milled and enzyme lignins were produced from abaca fibre via ball milling for 6 days followed by cellulase treatment for 3 days. The crude lignin preparations were fractionated into milled lignin (ML), enzyme lignin (EL), hemicellulose‐rich milled lignin (HRML), and lignin‐rich enzyme lignin (LREL) fractions using a two‐step precipitation method instead of a traditional ether precipitation procedure. The yield and chemical composition of the resulting lignin samples are reported. The ML and EL fractions contained low amounts of associated neutral sugars (2.0–3.3%) and uronic acids (1.4–1.5%), and showed relatively low average molecular weights (2500–2660), while the LREL and HRML fractions contained large amounts of bound polysaccharides (35.6–38.3%), and showed high molecular weights (8800–25000). The four lignin fractions are composed of a large proportion of syringyl units with fewer guaiacyl and p‐hydroxyphenyl units. The ML is mainly composed of β–O–4 ether bonds between the lignin structural units. The less common β–β, β–5 and 5–5′ carbon–carbon linkages are also present in the lignin molecules. It was found that uronic acids and 41–63% of p‐coumaric acids are esterified to lignin in the three lignin‐rich fractions of ML, EL and LREL. This level increased to over 90% in the hemicellulose‐rich fraction of HRML. For ferulic acids, 92–97% were found to be etherified to lignin in the three lignin‐rich fractions of ML, EL and LREL, while in the hemicellulose‐rich fraction of HRML this reduced to only 13%, suggesting that a majority of the ferulic acids are esterified to hemicelluloses or lignin in this fraction. © 1999 Society of Chemical Industry     

柠檬皮渣膳食纤维制备工艺研究

以柠檬皮渣为原料,分别采用水和95%的乙醇为溶剂在不同温度下制备柠檬膳食纤维,并测定其膳食纤维组成和理化特性。结果表明：柠檬膳食纤维制备的工艺条件采用水在室温下处理1min,并进行冷冻干燥,可以得到总黄酮含量、VC含量和持油力较好的产品;柠檬膳食纤维制备的工艺条件采用乙醇在60℃处理90min,并进行冷冻干燥,可以得到SDF/IDF（可溶性膳食纤维/不溶性膳食纤维）比值合理、持水力、粘度、白度都较好的产品。     

Characterisation of dietary fibre components in rye products

In this study, dietary fibre (DF) was characterised in rye products from a local supermarket. Soft breads generally had lower DF contents (8–18%) than had crisp breads (13–20%) due to high inclusion of wheat flour. For some products, the labelled DF values contained fructan, but others did not. However, for most products, the DF values analysed exceeded those declared. Arabinoxylan (AX) and fructan were generally the main DF components in the products, followed by cellulose and resistant starch, β-glucan, Klason lignin and arabinogalactan. In the soft breads, cellulose and resistant starch concentrations were relatively high, due to significant formation of resistant starch. During bread manufacturing, the molecular weight of β-glucan was highly degraded, while that of AX was more resistant. Extruded products had the highest β-glucan extractability and the extracted β-glucan retained its molecular weight most, which may be of nutritional significance. In rye milling fractions, about 50% of the fructan content analysed had a degree of polymerisation below 10, i.e. it comprised oligosaccharides. The crisp breads produced without yeast had the highest DF and fructan contents and the highest proportion of low-molecular weight fructan. These results indicate that, during bread-making, the low-molecular weight fraction of fructan was most available for degradation by yeast or by endogenous enzymes present in the ingredients.     

Evaluation of pretreatment with Pleurotus ostreatus for enzymatic hydrolysis of rice straw

The effects of biological pretreatment of rice straw using four white-rot fungi (Phanerochaete chrysosporium, Trametes versicolor, Ceriporiopsis subvermispora, and Pleurotus ostreatus) were evaluated on the basis of quantitative and structural changes in the components of the pretreated rice straw as well as susceptibility to enzymatic hydrolysis. Of these white-rot fungi, P. ostreatus selectively degraded the lignin fraction of rice straw rather than the holocellulose component. When rice straw (water content of 60%) was pretreated with P. ostreatus for 60 d, the total weight loss and the degree of Klason lignin degraded were 25% and 41%, respectively. After the pretreatment, the residual amounts of cellulose and hemicellulose were 83% and 52% of those in untreated rice straw, respectively. By enzymatic hydrolysis with a commercial cellulase preparation for 48 h, 52% holocellulose and 44% cellulose in the pretreated rice straw were solubilized. The net sugar yields based on the amounts of holocellulose and cellulose of untreated rice straw were 33% for total soluble sugar from holocellulose and 32% for glucose from cellulose. The SEM observations showed that the increase in susceptibility of rice straw to enzymatic hydrolysis by pretreatment with P. ostreatus is caused by partial degradation of the lignin seal. When the content of Klason lignin was less than 15% of the total weight of the pretreated straw, enhanced degrees of enzymatic solubilization of holocellulose and cellulose fractions were observed as the content of Klason lignin decreased.     

微波对膳食纤维结构和功能特性的影响

采用微波对甘薯渣、苹果渣、大豆渣中的膳食纤维进行改性,通过扫描电镜、X-射线衍射及热重分析,研究微波对3种膳食纤维结构的影响,并对比处理前后膳食纤维持水力、持油力、胆固醇吸附力、亚硝酸根离子吸附力的变化。结果表明：微波改性可以使膳食纤维的可及性边缘暴露,结晶度升高,热稳定性加强,且3种膳食纤维的功能特性均有不同程度改善,是一种优良的膳食纤维改性方法。此外,改性后3种膳食纤维中的可溶性纤维质量分数分别提高63.11%,4.51%,358.79%,与功能特性综合提高幅度并非正相关,改性后膳食纤维功能性质的提升是可溶性膳食纤维增加与不溶性膳食纤维可及性边缘的增加共同作用的结果。     

Relationship of cell wall composition to in vitro cell wall digestibility of maize inbred line stems

The phenolic equipment of maize stem tissues was investigated in relation to the feeding value of the detergent fibre components. Sixteen maize inbred lines, including three brown‐midrib 3 mutants and their normal counterparts, were selected for highly divergent in vitro cell wall digestibility. These lines were grown during two years. Maize stems were analysed for detergent fibre concentration, esterified and etherified p‐hydroxycinnamic acids, lignin content and structure and in vitro digestibility. A large genotypic variation was found for neutral detergent fibre, cell wall phenolic composition and cell wall digestibility. Within the normal maize lines the in vitro neutral detergent fibre digestibility (IVNDFD) of stem fractions was negatively correlated with their Klason lignin content. A multiple regression model based on esterified p‐coumaric acid and lignin composition as two explanatory variates accounted for 58% of the IVNDFD variation. In this study, three normal maize inbred lines displaying a lignin content and a cell wall digestibility level close to those observed in the three bm3 lines could be detected, which opens up new breeding avenues. © 2000 Society of Chemical Industry     

Fiber and lignin analysis in concentrate, forage, and feces: detergent versus enzymatic-chemical method

Hemicelluloses, cellulose, and lignin contents of contrasting feeds, with emphasis on concentrate ingredients and complete concentrates, were analyzed using the Van Soest detergent procedure (analyzing neutral detergent fiber, acid detergent fiber, and acid detergent lignin) and the enzymatic-chemical procedure (analyzing cellulose, soluble and insoluble noncellulosic polysaccharides, and Klason lignin). Also, feces from cows fed concentrates differing in carbohydrate composition were analyzed by the 2 procedures. The correlation between acid detergent lignin and Klason lignin was significant, but not as close as the one between individual structural polysaccharides measured with the 2 procedures. The correlation between the results of the 2 procedures was highly significant for apparent cellulose digestibility, as were the correlations between digestibilities of hemicelluloses with total as well as with insoluble noncellulosic polysaccharides. The relationship between dietary lignin content and fiber digestibility was weak. The exclusion of a group of cows fed a concentrate with apple pulp, however, improved the respective correlations. Klason lignin correlated more closely with the measured fiber digestibility than acid detergent lignin. The study showed that results of the detergent method were comparable to those of the enzymatic-chemical method with cellulose, hemicelluloses, and their digestibilities. However, acid detergent lignin was much lower than Klason lignin. When the carbohydrate composition of concentrate varied widely, lignin was not suitable for the prediction of fiber digestibility.     

Profile of fibre composition in lucerne (Medicago sativa) hay and rumen digesta as influenced by particle size and time after feeding

The chemical composition of fibre from lucerne (Medicago sativa L) hay and rumen digesta from a cow fed the hay, as well as the variation in fibre composition due to particle size and time post-feeding for the digesta, was examined. Neutral sugar residues accounted for the greatest proportion of the fibre in all samples. The feed contained equal amounts of uronic acid residues and Klason liynin, while in the digesta uronic acid residue contents were decreased and Klason lignin levels were increased. Esterified phenolics accounted for less than 0.5 % of the fibre in all samples. Glucose was the primary sugar residue in the fibre, but xylose levels increased substantially in the digesta. The levels of other sugar residues declined in the digesta relative to the feed. p-Coumaric and ferulic acids were the major esterified phenolics, and ferulic acid levels declined relative to the total phenolic acids in the digesta. The degree of variation in composition among particle size fractions or in digesta samples with time afer feeding were small relative to those observed between the feed and digesta. Invitro degradability reflected differences in fibre composition, with a large difference between lucerne hay and rumen digesta, but only minor differences among digesta samples collected from different times after feeding.