The phenolic acid and polysaccharide composition of cell walls of bran layers of mature wheat (Triticum aestivum L. cv. Avalon) grains

The purpose of this study was to examine the carbohydrate and phenolic‐ester composition of cell walls in wheat bran layers. Four defined layers of wheat bran were separated manually from mature grains of wheat (Triticum aestivum L. cv. Avalon) to give samples of beeswing bran (outer pericarp), cross cells, testa + nucellar epidermis and aleurone cells. The cell‐wall material from each layer, and from a sample of intact bran, was analysed for carbohydrates and wall‐bound esterified phenolic acids. The cell‐wall material of intact bran was rich in arabinose and xylose with significant quantities of glucose and uronic acid and a relatively small amount of galactose and mannose. The varying ratios of arabinose:xylose in cell walls of isolated bran layers indicated that the heteroxylans had tissue‐specific substitution patterns. HPLC analysis of phenolic acids identified significant amounts of esterified ferulic acid and 8‐8′‐ (aryltetralin form), 5‐8′‐, 5‐5′‐, 8‐0‐4′‐ and 5‐8′‐(benzofuran form)‐dehydrodiferulic acids in the isolated cell walls. Ferulic acid was highly concentrated in the aleurone layer, whereas dehydrodiferulates were concentrated in the beeswing bran and cross cells. The role of phenolic cross‐linking is discussed in relation to the architecture of the cell walls of wheat bran and to processing implications. Copyright © 2005 Society of Chemical Industry     

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     

Non-starch polysaccharides and bound phenolic acids from native and malted finger millet (Ragi,Eleusine coracana,Indaf - 15)

Nature of non-starch polysaccharides (NSP) and bound phenolic acids from native and malted ragi were studied using a recently-released hybrid variety of ragi, (Indaf-15). Yields of water-soluble NSP, hemicellulose-B and cellulose polysaccharides increased upon malting whereas a substantial decrease in the yield of hemicellulose-A was observed. Hemicellulose-B is the most viscogenic and its relative viscosity decreased from 3.04 to 1.98 upon 96 h of malting, whereas the solubility and viscosities of the rest of the NSP increased upon malting. The major sugars identified in all the NSP fractions were arabinose, xylose, galactose and glucose. A one- to two-fold decrease in arabinose was observed in all the NSP upon malting except for the alkali-insoluble residue wherein a decrease of glucose was observed. A progressive decrease in the pentose to hexose ratio was observed, indicating mainly pentosan degradation during malting, whereas an increase in the pentose to hexose ratio was observed in the alkaline-insoluble residue (AIR). Ferulic, caffeic and coumaric acids were identified as the major bound phenolic acids in native ragi and one- to two-fold decrease was observed in their contents after 4 days of malting.     

Structural characteristics of water-soluble feruloyl arabinoxylans from rice (Oryza sativa) and ragi (finger millet, Eleusine coracana): Variations upon malting

Water-soluble feruloyl arabinoxylans (feraxans), isolated from native and malted (96 h) rice (Oryza sativa) and ragi (Eleusine coracana) grains, were fractionated on DEAE-cellulose, followed by purification on Sephacryl S-300 and the homogeneity was ascertained by high performance size exclusion chromatography, cellulose acetate and capillary electrophoresis. Structural characterization of the purified polysaccharides by methylation, followed by GLC–MS, and also by ¹H NMR and ¹³C NMR spectroscopy, indicated very high branching and presence of high amounts of O-2 substituted xylans. The amount of O-2, 3 disubstituted xylopyranosyl residues and the arabinose:xylose ratio was higher in malt feraxans. All feraxan samples consumed almost equal amounts of periodate (4.02–4.30 μmol/mg). High amount of xylose (∼40%), as identified by Smith degradation, further substantiated the high branching of feraxans. A model is presented depicting the structure of water-soluble feraxans from rice and ragi and their changes upon malting.     

Release of phenolic acids from defatted rice bran by subcritical water treatment

BACKGROUND: Oil production from rice bran, an undervalued by‐product of rice milling, produces defatted rice bran (DRB) as a waste material. Although it is considered a less valuable product, DRB still contains useful substances such as phenolic compounds with antioxidant, UV‐B‐protecting and anti‐tumour activities. In this study the phenolic acids in DRB were extracted with subcritical water at temperatures of 125, 150, 175 and 200 °C. RESULTS: Analysis of total phenolics using Folin–Ciocalteu reagent showed about 2–20 g gallic acid equivalent kg^?1 bran in the extracts. High‐performance liquid chromatography analysis showed low contents of phenolic acids (about 0.4–2 g kg^?1 bran). Ferulic, p‐coumaric, gallic and caffeic acids were the major phenolic acids identified in the extracts. Thermal analysis of the phenolic acids was also done. The thermogravimetric curves showed that p‐coumaric, caffeic and ferulic acids started to decompose at about 170 °C, while gallic acid did not start to decompose until about 200 °C. CONCLUSION: Subcritical water can be used to hydrolyse rice bran and release phenolic compounds, but the high temperatures used in the extraction can also cause the decomposition of phenolic acids. Copyright © 2010 Society of Chemical Industry     

Color of whole-wheat foods prepared from a bright-white hard winter wheat and the phenolic acids in its coarse bran

Abstract: The color of wheat kernels often impacts the color and thereby the value of wheat‐based foods. A line of hard white winter wheat (B‐W HW) with bright appearing kernels has been developed at the Kansas State Agricultural Research Center. The objective of this study was to compare the color of several foods made from the B‐W HW wheat with those of 2 hard white wheat cultivars, Trego and Lakin. The B‐W HW kernels showed higher lightness (L*, 57.6) than Trego (55.5) and Lakin (56.8), and the increased lightness was carried over to its bran and whole‐wheat flour. Alkaline noodle and bread crumb made from the B‐W HW whole‐wheat flour showed slightly higher lightness (L*) than those made from Trego and Lakin. The sum of soluble and bound phenolics extracted from the 3 wheat brans, which had not been preextracted to remove lipids, was found to be 17.22 to 18.98 mg/g. The soluble phenolic acids in the brans were principally vanillic, ferulic, and syringic. The bound phenolic acids in the brans were dominated by ferulic, which accounted for 50.1% to 82.2% of total identified bound phenolic acids. Other bound phenolic acids were protocatechuic, caffeic, syringic, trans‐cinnamic, p‐hydroxybenzoic, p‐coumaric, and vanillic. The lightness (L*) values of coarse wheat brans correlated positively with their levels of bound protocatechuic (r = 0.72, P < 0.01) and p‐hydroxybenzoic acids (r = 0.75, P < 0.01).     

Bioactive xylo-oligosaccharides from wheat bran soluble polysaccharides

Soluble polysaccharides (SP, 35 g) isolated from wheat bran (100 g) consisted mainly of arabinose and xylose with minor quantities of rhamnose, mannose, galactose and glucose. Wheat bran SP was subjected to purified endoxylanase (from 96 h ragi malt) treatment to obtain xylo-oligosaccharides (0.3 g/1 g wheat bran). The oligosaccharide mixture was purified on Biogel P-2 column into four major peaks designated as WO-1, WO-2, WO-3 and WO-4. Individual oligosaccharide purity was ascertained by HPLC and their composition was determined by GLC. The purified oligosaccharides were characterized by ESI-MS and ¹H NMR analysis. WO-1 and WO-2 were identified as arabinose containing xylotetraose and xylotriose, respectively, whereas WO-3 and WO-4 were identified as unsubstituted xylotriose and xylobiose, respectively. In vitro studies carried out using Bifidobacterium spp and Lactobacillus spp suggested the prebiotic nature of the crude as well as purified xylo-oligosaccharides as revealed by growth characteristics such as high O.D. of the culture broth, decrease in its pH, increase in cell mass and the resultant fermentation products. β-xylanase, β-xylosidase, α-arabinofuranosidase, α/β-galactosidases and acetyl esterase activities were determined in 24 h old culture broth and xylanase activity (440-830 μU/ml) was found to be the most preponderant among all of them.     

Rumen degradation of cell wall polysaccharides in untreated and alkali-treated straws and cereal brans

Rumen degradation of cell wall polysaccharide constituents using the in sacco technique was studied for untreated cereal brans (oats, wheat and barley) and nine technically alkali-treated batches of barley straw. The alkali treatment included four ammonia treatments, two dry sodium hydroxide treatments and three wet sodium hydroxide treatments. On degradation of the cell wall polysaccharides, their main constituents, xylose and glucose, were released at about the same rate for the ammonia treatments and the dry sodium hydroxide treatments. For the wet sodium hydroxide treatments the degradation of the xylose residues was faster than the liberation of the glucose residues. For all treatments the liberation of the arabinose residues was faster than that of the xylose and glucose residues. The reason for the increased digestibility of the cell wall polysaccharides is suggested to be the breaking of ester and hydrogen bonds and the breaking of alkali-labile linkages in lignin, as well as changes in the surface layer of the straw. For the wet sodium hydroxide treatments the larger amount of water present during the alkali treatment processes is suggested to increase the diffusion of the alkali into the straw and to translocate a part of the hemicellulose. On the degradation of wheat and barley bran the liberation of xylose residues was fast whereas xylose and arabinose residues in oat bran were slowly liberated.     

Antioxidant activities and phenolic compounds of pigmented rice bran extracts

This study was carried out to investigate the antioxidant activities and phenolic compounds of pigmented rice (black, red, and green rice) and brown rice brans. Antioxidant activity was determined by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay, 2,2-azino-bis-(3-ethylenebenzothiozoline-6-sulfonic acid) (ABTS) radical cation assay, reducing power, and chelating ability. Phenolic compounds were measured by using HPLC. Pigmented rice brans were extracted by using aqueous mixtures of acetone, ethanol, and methanol to determine the most effective extraction solvent. Of all solvents examined, extract from 40:60 acetone-water mixtures (v/v) provided the highest DPPH radical assay as well as the highest total phenolic and flavonoid content. We finally selected 40% acetone as an extraction solvent for antioxidant study of pigmented rice bran. Antioxidant activities of 40% acetone extracts of pigmented rice bran, measured in the range of 0 to 1500 μg/mL. At 500 μg/mL concentration, red rice bran, which had the highest total phenolic (259.5 μg/mg) and total flavonoid (187.4 μg/mg) contents, showed the highest antioxidant activity: 83.6%, 71.5%, 1.2%, and 16.4% for DPPH radical assay, ABTS radical cation assay, reducing power, and chelating ability, respectively. Red rice bran showed a lower EC(50) value (112.6 μg/mL) than that of butylated hydroxytoluene (144.5 μg/mL) from the DPPH radical assay. The major phenolic acids of red rice bran were ferulic, vanillic and p-coumaric acids. The results indicated pigmented rice bran might be used as a natural antioxidant. PRACTICAL APPLICATION: The present study revealed black and red rice bran shows high antioxidant activities and they contain high amount of phenolic compounds. Indeed, black and red rice bran could be better raw materials for manufacturing the food with high antioxidant activity.     

The influence of ultrasonic modification on arabinoxylans properties obtained from wheat bran

This work is concerned with modification of wheat bran arabinoxylans by ultrasound irradiation. The average molecular weights of arabinoxylans ranging from 580 000 to 800 000 kDa were yielded by regulating ultrasonic powder (120–480 W) and treat time (15–45 min). The phenolic compounds increased after ultrasound treatment, and arabinose‐to‐xylose ratios ranged between 0.55 and 0.67. FTIR spectroscopy revealed that the major chemical composition of arabinoxylans was unchanged. The maximum storage modulus decreased with the extension of ultrasonic treatment time. The antioxidant capacity test showed that the EC₅₀ values decreased and the values from the ferric reducing antioxidant power decreased after ultrasound treatment. The results suggested that ultrasound is an effective method for the modification of arabinoxylans.     

Structural characterisation of a water-soluble polysaccharide with high branches from the leaves of Taxus chinensis var. mairei

A large number of polysaccharides present in the leaves of Taxus chinensis var. mairei were successively extracted with hot water after preliminary treatments. The ion-exchange and gel-permeation chromatography was used to isolate and purify the major polysaccharides to afford a complex water-soluble polysaccharide, named T1 with a molecular mass of 3.44 × 10⁶ Da determined by HPGPC. T1 consisted of 2,4-di-O-methyl-mannose, rhamnose, arabinose, xylose, galactose, mannose, galacturonic acid and glucuronic acid in a molar ratio of 2:5:24:9:3:46:1:10, and the acetyl content was estimated to be 2.1%. On the basis of methylation analysis, periodate and chromium trioxide oxidations, Smith degradation, graded acid hydrolysis, and NMR and IR spectroscopy, T1 possessed a 1,3,6-linked β-d-Manp main chain, substituted by mannose, arabinose, galactose, xylose, rhamnose, 2,4-di-O-methyl-mannose, galacturonic acid, and glucuronic acid residues. These contained non-reducing end-units of mannose, arabinose, xylose, 2,4-di-O-methyl-mannose, and glucuronic acid. This is the first report on isolation of an acid heteropolysaccharide from Taxus species.     

Starch and cell wall degrading enzymes from fungal organisms grown on cereal and millet brans

In the global market, there has been an increasing demand for natural products. In this direction, the present study has attempted to evaluate fungal organisms as a source of starch and cell wall degrading enzymes which have a role to play in obtaining ferulic acid from brans of cereal and millet and are subsequently biotransformed to vanillin. Three fungal organisms, namely Aspergillus niger CFR 1105, A. oryzae CFR 232 and Rhizopus arrhizus NCIM 997, were grown on brans of wheat, rice and ragi (Eleusine coracana) for 24-, 48-, 72- and 96-h time intervals, and the resultant moldy brans were evaluated for starch and cell wall degrading enzymes. The activity of amylase, the most preponderant enzyme in all the moldy brans, was several times higher than the pullulanse activity. Xylanase activity was 2–3 times higher than that of 1,3/1,4--D-glucanase in all the moldy brans. A. niger CFR 1105 and A. oryzae CFR 232 were found to be better than R. arrhizus NCIM 997 with respect to the induction of starch and cell wall degrading enzymes and can be utilized for the degradation of cell wall polymers of wheat, rice and ragi brans. Wheat bran was found to be a better substrate than rice and ragi brans for the induction of those enzymes.Presented at the 5th International Food Convention, held at CFTRI, Mysore, India, 5--8 December 2003.     

Phenolic acid concentrations in organically and conventionally cultivated spring and winter wheat

BACKGROUND: Organic crops are often thought to contain more phenolic secondary metabolites than conventional ones. This study evaluated the influence of organic and conventional farming on concentrations of phenolic acids in spring and winter wheat cultivars. RESULTS: Five phenolic acids were identified: ferulic, sinapic, p‐coumaric, vanillic and p‐hydroxybenzoic acid. Ferulic acid was the main phenolic acid in the grain of all tested wheat varieties. Significant differences among the examined cultivars in concentration of particular compounds were observed. Concentrations of phenolic acids varied significantly in organic and conventional wheat. Levels of ferulic and p‐coumaric acids, as well as the total phenolic acid content were higher in organic crops. Concentrations of sinapic acid in spring wheat, as well as vanillic and p‐hydroxybenzoic acid levels in both types of wheat were significantly higher in conventional grains. The 1000 kernel weight (TKW) of spring and winter wheat was significantly lower in organic crops. CONCLUSION: Organically produced spring and winter wheat had significantly higher concentrations of ferulic and p‐coumaric acid as well as the total phenolic acid content than conventional wheat, though the differences in the levels of phenolics were not large. However, these differences are probably caused mainly by smaller size of organic wheat kernels (lower TKW). Copyright © 2011 Society of Chemical Industry     

A comparative study on free and bound phenolic acid content and their antioxidant activity in bran of rice (Oryza sativa L.) cultivars of Eastern Himalayan range

In our study, seven most prevailing but unexplored indigenous rice cultivars of northeast India, situated in the Eastern Himalayan Range, were investigated for their phenolic acid profile, total phenolic content (TPC) and antioxidant capacities in free and bound phenolic extracts of their bran. HPLC studies showed the presence of ferulic, p‐coumaric, sinapic, caffeic, chlorogenic and vanillic acids, with ferulic and p‐coumaric acids being the dominant phenolic acids in the bound form. The lower EC₅₀ values of the bound extracts than the free extracts suggested the better radical scavenging activity of the bound extracts. Significant correlations were observed between TPC and phenolic acid content (HPLC‐DAD) of bound extracts, and between Trolox equivalents antioxidant capacity (TEAC) and phenolic acid content (HPLC‐DAD) of both free and bound extracts. The findings suggest that phenolic acids in the rice cultivars investigated were exclusively present in bound form and contribute significantly towards their antioxidant capacity.     

The analysis of phenolic constituents in glabrous canaryseed groats

Nineteen glabrous canaryseed samples, comprising brown- and yellow-coloured seeds, were investigated to determine the nature of phenolic constituents present. Total phenolic content (TPC) was determined, using the Folin–Ciocalteau assay. Flavonoid and phenolic acid compositions were determined, using high performance liquid chromatographic and mass spectrometric (LC–MS/MS) techniques. TPC ranged from 174 to 209 mg/100 g for canaryseed wholemeal samples. The canaryseed bran contained twice as much TPC as the wholemeal. The brown- and yellow-coloured whole canaryseeds exhibited the same flavonoid profiles. LC–MS/MS analysis showed that the canaryseed acetone extract was rich in flavonoid glycosides, with the bran being mainly composed of O-pentosyl isovitexin and the flour having a compound at m/z 468. No proanthocyanidins were detected in the 19 samples. Ferulic acid was the dominant phenolic acid, followed by caffeic and p-coumaric acids. The wholemeal obtained from the brown-coloured group had significantly higher contents of ferulic (>196 mg/kg) and caffeic (>96 mg/kg) acids in comparison to the yellow-coloured canaryseed group. The latter had ferulic and caffeic acids at levels less than 165 and 78 mg/kg, respectively, with one exception which had relatively higher levels (190 and 94 mg/kg). Whilst canaryseed flour contained significantly very low levels of ferulic acid (22–34 mg/kg), the bran was enriched in ferulic (593–766 mg/kg), caffeic (304–452 mg/kg) and p-coumaric (119–142 mg/kg) acids.     

In vitro digestibility and colonic fermentability of aleurone isolated from wheat bran

Two aleurone preparations, isolated from wheat bran, with different levels of tissue purity, were compared to the wheat bran starting material. Chemical composition, in vitro digestibility and in vitro fermentability were investigated and microscopy was used to visualize morphological changes. Arabinoxylans constituted the main part of the dietary fibre fraction. However, the degree of branching was found to be lower in arabinoxylans from aleurone than in that from original bran. Due to the high fibre content, in vitro digestibility was rather low but digestible compounds were largely eliminated. In vitro fermentability using fresh human faecal material turned out to be higher in aleurone than in wheat bran. Moreover, the degree of purity of the aleurone preparations influenced the amount of fermentation products. Proportions of the main short chain fatty acids were very similar in all samples, with ratios of propionate and butyrate slightly above average compared to other dietary fibre sources. Arabinoxylans from aleurone were virtually completely degraded within 8 h, whereas with wheat bran, substantial amounts were still present after 24 h. Moreover, increasing arabinose:xylose ratios during fermentation suggested a better fermentability of arabinoxylans with a lower branching degree. Microscopic investigations confirmed the better fermentability of aleurone compared to wheat bran. In addition, a specific breakdown pattern of aleurone cell walls could be observed.     

Maize bran/oat flour extruded breakfast cereal: A novel source of complex polysaccharides and an antioxidant

A maize bran/oat flour extruded breakfast cereal was developed as a novel source of an antioxidant and complex polysaccharides. Six levels of maize bran/oat flour were formulated (0, 10, 20, 30, 40 and 50%, w/w). The breakfast cereal containing 30% maize bran was the most accepted by consumers. A 100 g serving of this cereal formulation provides 0.2 g of ferulic acid, and 8 g of complex polysaccharides, which includes 1.2 g of β-glucans and 6.8 g of arabinoxylans. This cereal breakfast could be an alternative to maize bran, which is a by-product scarcely used for human consumption.     

Studies on the free sugars,water-soluble gums and hemicelluloses from barley grains and malts

The free sugars, water-soluble gums, and hemicelluloses have been isolated from four barley grain samples [Hordeum vulgare (L.)], and from their commercial malts. Arabinose, xylose, galactose, glucose, fructose, maltose and sucrose occur as free sugars in the grains and the proportions of these sugars increase on malting. Mannose also occurs as a free sugar in the malts. The water-soluble gums contain arabinose, xylose, lesser amounts of mannose and galactose, and varying amounts of glucose. The aqueous-ethanol supernatants from the hot-water extracts are glucans of low molecular weight. The hemicellulose A polymers contain arabinose, xylose, mannose and glucose. Wide variations in the mannose and glucose contents were observed in these polysaccharides. The hemicellulose B polymers are arabinoxylans, containing lesser amounts of galactose and glucose. The aqueous-ethanol supernatants from the hemicellulose B precipitations contain arabinose, xylose, mannose, galactose and glucose. These polysaccharides differ markedly from those present in the aqueous-ethanol supernatants of the hot-water extracts. All polysaccharides are modified to varying degrees during malting.     

Carbohydrate composition of wheat,wheat bran,sorghum and bajra with good chapati/roti (Indian flat bread) making quality

Varieties of wheat, sorghum and bajra having good chapati/roti making quality were studied for carbohydrate profile. Polysaccharide fractions (water-soluble, barium hydroxide-soluble, alkali-soluble and insoluble) were isolated from these cereals and wheat bran and their carbohydrate profiles were studied. Arabinoxylans were the major polysaccharides, other than starch and cellulose. The ratio of arabinose to xylose in whole-wheat flour and wheat bran was nearly 1.25:1 but the hemicellulose A in wheat flour was mainly xylan-type. Among the pentosans in barium hydroxide extract of sorghum, the hemicellulose A had more arabinose than xylose, but the hemicellulose B contained nearly equal amounts of arabinose and xylose. Bajra had arabinose and xylose in nearly equal amounts in both the barium hydroxide extract and alkali-soluble fractions. The alkali-insoluble residues were complexes of pentosans with cellulose and were strongly bound. Contents of dietary fibre varied between the cereals. Wheat bran had the highest among the four.