Influence of solvent extraction on the dietary fibre fractions of alfalfa protein concentrates

“Freezing curd” was prepared from alfalfa juice and extracted with 2-propanol, either untreated or after washing with water. The soluble and insoluble dietary fibre fractions of the two extracted concentrates and the unextracted freezing concentrate were analysed to assess the effect of extraction on fibre content. Compared with unextracted “freezing curd”, direct extraction with 2-propanol without washing increased the insoluble and soluble dietary fibre fractions by approximately 55% and 52% respectively, while washing with water followed by extraction with organic solvent led to an increase of about 79% and 28%, respectively. Thus, the washing with water lowered the soluble fibre by around 16%. Analysis of the ash and proteins in the crude fibre residues showed that while the ash content was similar in the residues for both the soluble and insoluble fibre, the protein content was much higher in the insoluble fibre residue.     

The influence of rice fibre fractions on the in vitro fermentation production of short chain fatty acids using human faecal micro flora

A study was conducted to assess the effects of rice dietary fibre on the fermentative activity of human faecal microflora. Dietary fibre was extracted from four commercially available Sri Lankan rice varieties [LD 356, AT 353 (red in colour); BG 352, and BG 358 (white in colour)], and separated into individual fractions of total dietary fibre (TDF), insoluble dietary fibre (IDF) and soluble dietary fibre (SDF). Four healthy human subjects were given a diet containing the four rice varieties for more than 4 months prior to the study. Faecal microflora was obtained from human volunteers, after the 4 months of rice based diet, and used for anaerobic fermentation of the individual rice fibres. Short Chain Fatty Acid (SCFA) production was analysed at 0, 2, 4, 6 and 24 h by gas liquid chromatography. Among the SCFA, acetate was the most abundant acid formed in all rice varieties. The fibre fractions from rice variety LD 356 (TDF16.73%, SDF 3.57%, 11.9% IDF) gave the highest yield of SCFA while the variety BG 358 gave the least. Total dietary fibre of all rice varieties contributed to produce more SCFA than the individual soluble dietary fibre and insoluble dietary fibre fractions.     

Antioxidant activity and dietary fibre in durum wheat bran by-products

Milling of wheat generates by-products, which can be used to improve the technological performance and/or to integrate foods with healthy compounds. The aim of this paper was to select fractions of durum wheat bran having different functional and nutritional characteristics. Wheat bran by-products were obtained by an industrial milling process. Beside the single fractions, two commercial products Bran & Brain 50 and 70, obtained by blending some of the durum wheat fractions were also studied. All samples were investigated for water holding capacity, soluble and insoluble dietary fibre content and for their antioxidant activity. The soluble fibre content of the durum wheat by-product ranged between 0.9% and 4.1%; while that of insoluble fibre between 21% and 64%. B&B 70 has a TDF content of 61%, while B&B 50 has 42%. The water holding capacity of each fraction is strictly related to the amount of insoluble fibre and to the granulometry of the by-products. Cooking-extrusion process does not affect the amount of soluble fibre; by contrast, a significant increase of the insoluble fibre was detected. The antioxidant activity is higher for the internal bran fraction and it increases in fractions having reduced granulometry. The antioxidant activity of some durum wheat by-product fractions is comparable to that of widespread fruits and fresh vegetables, likely due to the presence of fibre-bound phenol compounds. The high fibre content and antioxidant activity of durum wheat bran by-products can be of particular interest for their use in cereal-based products.     

Storage of fresh and ensiled forages by freezing affects fibre and crude protein fractions

The effect of freezing on fibre and crude protein fractions of forages was determined. Fresh and ensiled lucerne and fresh bromegrass were processed immediately after collection or stored at ?25°C for 1 day or 1, 6 or 12 months before drying at 55°C. Samples were frozen quickly by submersion in liquid nitrogen or slowly at ?25°C. Samples which were not frozen were processed immediately or after 1 h delay at room temperature. All treatments were replicated (n = 3). Samples were analysed for crude protein (CP), trichloroacetic acid soluble CP (TSCP), phosphate buffer soluble CP (BSCP), neutral detergent insoluble CP (NDCP), acid detergent insoluble CP (ADCP), neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent sulphuric acid lignin (lignin) and ash. Freezing decreased BSCP and increased NDCP by more than 40% for bromegrass. Freezing also changed NDF, ADF, lignin, ash, CP and ADCP in different ways depending on forage type and length of time frozen. No significant effects were observed for method of freezing or a 1-h delay in processing. An additional experiment showed that freeze-drying resulted in less insoluble protein than ovendrying. Prior freezing of forages appeared inconsistently to change the extent of gaseous loss during drying, and resulted in precipitation of protein. These changes also affected fibre estimates. Fresh forages should not be frozen and thawed before analysis of protein or fibre fractions.     

Identification of gas‐producing components in different varieties of Phaseolus vulgaris by in vitro fermentation

Phaseolus vulgaris consumption has been limited as part of the occidental diet owing to flatulence production. Raffinose, stachyose and verbascose have been shown to be the main components responsible for flatulence; however, it is thought that soluble fibre could also be involved in this phenomenon. The aim of the present study was to identify the main components of beans influencing flatus. Ten varieties of P vulgaris originating from South America were first analysed for their main nutrient and carbohydrate fractions. Three of the varieties were then fractionated to extract soluble and insoluble fibres. Various combinations of α‐galactosides and soluble and insoluble fibre fractions, in similar proportions to those contained in cooked grains, were used as substrates for in vitro fermentation studies using human faecal inoculum to determine the fermentative capacity of each of the three fractions. Considering the white varieties, total gas production and acidification of the medium were correlated with fermented organic matter from soluble fibre (R² = 1)) and with α‐galactosides (R² = 0.75). On the other hand, tannins present in pigmented varieties did not seem to interfere significantly in fermentation of soluble fibre. The total production of gas per gram of mixed fractions of soluble fibre and α‐galactosides in proportions found in cooked grains was lower than that expected from each substrate separately. It can be concluded that soluble fibre and α‐galactosides are good substrates for endogenous colonic flora subjected to in vitro fermentation studies and are thus responsible for flatulence induced by legume consumption. © 2001 Society of Chemical Industry     

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     

Mineral composition of isolated fibre fractions from artichoke and the effect of phosphate buffer on its structure and mineral content

Soluble and insoluble dietary fibre of artichoke heart were extracted in water and phosphate buffer to determine their mineral contents and to evaluate the effect of the extraction medium on fibre structure (studied by scanning electron microscopy) and mineral composition (determined by X-ray microanalysis and atomic absorption spectrophotometry). The undialysed soluble dietary fibre extracted with phosphate buffer showed a different structural organisation from that extracted with water. X-Ray microanalysis of both soluble fractions showed some differences between the Na, K, Ca and P contents, and also between the Na contents of the insoluble fractions. However, when the samples were dialysed, differences in morphology and structure between the soluble fractions were not observed. A study of the mineral composition by atomic absorption showed differences between both soluble fractions and both insoluble fractions as regards Na, Ca, Mg and Fe.     

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.     

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.     

利用牛蒡渣提取高活性膳食纤维的工艺

以牛蒡渣为原料 ,提取水溶性膳食纤维和水不溶性膳食纤维。正交试验结果表明 ,提取水溶性膳食纤维的适宜条件为 :温度 80℃ ,pH 2 0 ,时间 90min ,V (原料 ) :V (水 ) =1∶10 ,得率为1 0 % (以干渣计 ) ,成品色泽呈淡黄色 ,气味较好 ;水不溶性膳食纤维的提取条件为 :温度 60℃ ,pH2 0 ,时间 60min ,V (原料 )∶V(水 ) =1∶5 ,得率为 8 5 % (以干渣计 ) ,成品色泽呈白色 ,气味淡 ,其膨胀力高达 6 5mL/g ,持水力为 72 0 %     

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.     

Effect of low‐energy X‐ray irradiation on physical,chemical, textural and sensory properties of Dates

The effect of X‐ray irradiation as postharvest treatment on physical, chemical, textural and sensory attributes of Khalas dates (Phoenix dactylifera L.) was investigated. The surface of dates was subjected to low‐energy X‐ray irradiation at 3, 5 and 7 KGy. While some physical and chemical properties of dates were significantly different between treatments (fruit hardness, crude protein, total fat, tannins, total fibre and insoluble fibre), there was no detrimental effect on the quality (crude fibre, soluble dietary fibre, sucrose, glucose, fructose, moisture, total soluble solids, pH, water activity, colour and sensory evaluation). The sensory acceptability of X‐ray irradiated dates was significantly lower at 5 and 7 KGy than for untreated control. Irradiation at 3 KGy did not contribute to significant changes in physical, chemical or textural properties of dates. Adaptation to low‐energy X‐ray irradiation can be used as a potential commercial treatment for retaining the quality and ensuring the safety of dates.     

Effects of enzymatic treatment conditions on dietary fibre content of wheat bran and use of cellulase-treated bran in cookie

A commercial cellulase preparation (Viscozyme Cassava C) was employed to process wheat bran to improve the ratio of insoluble to soluble dietary fibre. The effects of initial moisture content, enzyme dosage, and incubation time on the content of soluble and insoluble fibre during the enzymatic treatment were investigated. The appropriate conditions for the cellulase treatment were initial moisture content of 0.75 g water g⁻¹ dry matter, enzyme dosage of 9 U g⁻¹ dry matter and incubation time of 120 min under which the ratio of insoluble to soluble fibre of wheat bran was lowered by 42%. Untreated and cellulase-treated wheat bran was incorporated into cookies at levels of 0%, 20%, 30%, 40% and 50%. Cookie with 50% cellulase-treated bran showed 21% lower ratio of insoluble to soluble fibre as well as 14% lower hardness and 13% higher overall acceptability than sample with the same amount of untreated bran.     

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     

Dietary fibre fractions in cereal foods measured by a new integrated AOAC method

The reliable determination of soluble, insoluble and total dietary fibre in baked goods and cereal flours is an important issue for research, nutritional labelling and marketing. We compared total dietary fibre (TDF) contents of selected cereal based foods determined by AOAC Method 991.43 and the new AOAC Method 2009.01. Fifteen bread and bakery products were included in the study. Our results showed that TDF values of cereal products determined by AOAC Method 2009.01 were always significantly higher than those determined by AOAC Method 991.43. This was explained by the inclusion of low molecular weight soluble fibre fractions and resistant starch fractions in the TDF measurement by AOAC 2009.01. This documents that nutritional labelling of cereal products poses the challenge how to update TDF data in nutrient databases in a reasonable time with an acceptable expenditure.     

Preparation and analysis of dietary fibre constituents in whole grain from hulled and hull-less barley

Sixteen different barley samples (7 of which were hull-less; H-L) were milled and subjected to pre-extraction with ethanol and hexane. Water soluble materials (WSM-TP-AI), containing mostly β-glucans, were purified from the hot water extracts by the use of heat-stable amylase. Crude arabinoxylans were extracted by an alkali solution (WUM-B-S) and purified by the use of β-glucanase and amyloglucosidase, giving AX. Finally insoluble fibre residues were obtained (WUM-B-R). GC and NMR analyses revealed no marked quantitative and qualitative differences of β-glucans or the water-soluble arabinoxylans in WSM-TP-AI between the H-L and the hulled (H) varieties. Significant differences among the two barley types were found in the Ara/Xyl ratio of the starting materials as well as the alkali soluble material (WUM-B-S) and the alkali insoluble residue (WUM-B-R). For alkali soluble AX the H samples had the lowest arabinose content. A single-tube preparative isolation procedure for starch-free barley fibre was used. Combined with NMR and GC this is a tool to produce defined fibre fractions for biological testing.     

Changes in Hydrogen Sulfide and Sulfhydryl Content of Heated Beef Adipose Tissue

SUMMARY— Beef adipose tissue was separated into the water soluble, salt soluble and insoluble (water-salt-ether) fractions, and the amount of H, S evolved upon heating each of the fractions was determined. The yield of H, S per 100 g of adipose tissue was 17.6, 1.7 and 5.5 μM for the water soluble, salt soluble and insoluble fractions, respectively. Thus, the water soluble fraction contributed about 71% of the H, S, while the corresponding contributions from the salt soluble and the insoluble fractions amounted to approximately 7 and 22%, respectively.     

Improvement of the functionality of a potential fruit insoluble fibre by micron technology

An insoluble food fibre was micronised to different microsizes (6.77–29.5 μm) by three different micron technologies using optimised conditions. The effects of different micronisation treatments and particle sizes on the characteristics and various physicochemical properties of this insoluble fibre were studied. As particle size decreased, the bulk density of the insoluble fibre was significantly (P < 0.05) decreased. A redistribution of fibre components from insoluble to soluble fractions was observed. The treatments, especially the high‐pressure micronisation, effectively (P < 0.05) increased the physicochemical properties (e.g. water‐holding capacity, swelling capacity, oil‐holding capacity, cation‐exchange capacity and glucose‐adsorption capacity) and also the inhibitory activity towards α‐amylase and pancreatic lipase of the insoluble fibre to different extent (from several up to c. fifteenfold). Our results suggested that micronisation treatments would provide an opportunity to improve the functionality of the insoluble fibre and exploit its potential applications as a functional ingredient in fibre‐rich products.     

Wet Fractionation of Hard-to-Cook Bean (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.) Seeds and Characterization of Protein,Starch and Fibre Fractions

A 2³ factorial design with four replicates of the central trial was used to evaluate wet-fractionation conditions for complete use of hard-to-cook (Phaseolus vulgaris L.) seeds. Tested variables were flour/water ratio (1:5, 1:7.5 and 1:10 w/v), pH (8, 9.5 and 11) and a soaking time (1, 2 and 3 h). The optimum conditions (1:10 w/v flour/water ratio; pH 8; and 1 h soaking time) were determined by the percentages of protein and starch recovery. Three fractions were obtained by the process: a protein isolate, starch fraction and fibrous residue. Isolate crude protein content was 73.03%; its in vitro digestibility was 76.7%, and its amino acids concentrations, except for methionine and cysteine, met essential amino acids requirements for preschool children and adults. Total starch content was 71.41% with an amylose content of 21.46% and an amylopectin content of 78.54%. Total dietary fibre in the fibrous residue was 42.12%, with 81.10% insoluble fibre and 18.91% soluble fibre. The protein isolate’s high protein content, the purity of the starch fraction and high proportion of insoluble fibre in the fibrous residues show wet fractionated hard-to-cook bean to be a promising source of functional ingredients with possible food industry applications.