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1.
To produce safe and healthy whole wheat food products, various grain or bran dry fractionation processes have been developed recently. In order to control the quality of the products and to adapt these processes, it is important to be able to monitor the grain tissue proportions in the different milling fractions produced. Accordingly, a quantitative method based on biochemical markers has been developed for the assessment of grain tissue proportions in grain fractions. Grain tissues that were quantified were the outer pericarp, an intermediate layer (including the outer pericarp, the testa and the hyaline layer), the aleurone cell walls, the aleurone cell contents, the endosperm and the germ, for two grain cultivars (Tiger and Crousty). Grain tissues were dissected by hand and analysed. Biochemical markers chosen were ferulic acid trimer, alkylresorcinols, para-coumaric acid, phytic acid, starch and wheat germ agglutinin, for outer pericarp, intermediate layer, aleurone cell walls, aleurone cell contents, endosperm and germ respectively. The results of tissue quantification by hand dissection and by calculation were compared and the sensitivity of the method was regarded as good (mean relative errors of 4% and 8% for Crousty and Tiger outer layers respectively). The impact of the analytical variability (maximum 13% relative error on coarse bran) was also regarded as acceptable. Wheat germ agglutinin seems to be a promising marker of wheat germ: even if the quantification method was not able to quantify the germ proportions in milling fractions, it was able to classify these fractions according to their germ content. The efficiency of this method was tested, by assessing the grain tissue proportions of fractions exhibiting very different compositions such as flour, bran and aleurone-rich fractions obtained from three different grain or bran dry fractionation processes (conventional milling, debranning process, production of aleurone-rich fractions from coarse bran). By calculation of the composition of the different products generated, it was possible to study the distribution of the different tissues among fractions resulting from the different fractionation processes. This quantitative method is thus a useful tool for the monitoring and improvement of processes, and allows the effects of these processes to be understood and their adaption to reach the objectives.  相似文献   

2.
Wheat bran tissue fractionation using biochemical markers   总被引：1，自引：0，他引：1  
Phenolic acid analysis of hand-isolated outer grain layers and endosperm led to the identification of markers of pericarp and aleurone layers, respectively. A new dehydrotrimer of ferulic acid (DHT) was found to be concentrated in the outer pericarp of wheat bran whereas p-coumaric (p-CA) acid was mainly in the aleurone layer. Phytates were also used as a marker of aleurone layer and starch as a marker of starchy endosperm. Biochemical markers constitute an original method for determining the histological composition of any technological bran fractions. A pin milling process was applied to coarse bran produced by a conventional milling process. Three different fractions (B1, B2 and B3) were obtained by sieving the bran products and then the smallest bran particle fraction (B3) was air-classified to obtain two particle size fractions (B3a and B3b with a D50 of 83 and 7 μm, respectively). The biochemical composition of these fractions was used to calculate the distribution of tissues according to the sieving process. The dissociation behavior of individual bran tissues upon mechanical fractionation was investigated in relation to particle size and discussed according to their mechanical properties.  相似文献   

3.
Ultra-fine grinding increases the antioxidant capacity of wheat bran   总被引：1，自引：0，他引：1  
In order to study the influence of wheat bran particle size on its antioxidant capacity, the wheat bran was ground under normal and cryogenic conditions with variable intensity to produce ten fractions with different physical structures. The high energy grinding increased 3-fold the specific surface of the bran fractions and also the proportion of particles smaller than 50 μm assimilated to the proportion of disrupted aleurone cells. All the ground bran fractions presented similar total ferulic acid concentration and chemical form (free, conjugated, linked). A positive effect of the grinding on the antioxidant capacity of the bran fractions was noticed. The antioxidant capacity increased from 30 to 45 mmol TEAC/kg when the specific surface increased from 0.09 to 0.26–0.30 m2/g. The antioxidant capacity of the bran fractions was linearly correlated with the specific surface, with the D50 values and with the proportion of particles smaller than 50 μm. In in vitro gastric conditions, the finely ground bran inhibited the accumulation of conjugated dienes more efficiently than coarse bran. In conclusion, the bran structure affects its antioxidant capacity. This effect remained in gastric conditions showing that grinding can be used to produce wheat bran fractions with higher nutritional value.  相似文献   

4.
The three major botanical components (starchy endosperm, aleurone layer and pericarp) of eight durum wheat samples exhibited significantly different compositions and concentrations in phenolic acids. The starchy endosperm, the aleurone layer and the pericarp were respectively characterised by a low content in ferulic acid (FA), a high content intrans -sinapic acid (t -SA), and a high content in ferulic acid dehydrodimers (DHD). These three chemical markers can be exploited to differentiate the three grain botanical parts within milling fractions and to evaluate the milling efficiency, particularly the separation between bran and endosperm. The histological dissociation of the wheat grain generated by the milling process can be investigated further into details using the three phenolic acids markers. A separability index (S i) was proposed in order to quantify the ease of dissociation of endosperm from bran. Differences in S i values between wheat varieties grown under various agricultural conditions demonstrated the relevant variability of this character. The structural and molecular factors implied in the control of tissue dissociation are discussed in details.  相似文献   

5.
Hand dissection of mature grains from two common wheats (Triticum aestivum L., cv. Caphorn and cv. Crousty) were performed to quantitatively assess their tissue composition and to obtain homogeneous samples of embryonic axis, scutellum, starchy endosperm, aleurone layer, hyaline layer, outer pericarp and a composite layer made up of testa+hyaline layer+inner pericarp. Polymeric neutral sugar and phenolic acid contents of the samples were determined and used to identify specific composition patterns in each tissue irrespective of the cultivar. The scutellum and embryonic axis showed the lowest amount of carbohydrates with similar relative amounts of arabinose and xylose (Ara+Xyl), but the scutellum differed from the embryonic axis in its high phenolic acid, in particular ferulate dehydrodimer, content. The peripheral layers of the grains were mainly composed of cell wall polysaccharides, chiefly arabinoxylans but with differing structures. The hyaline layer was mostly composed of arabinoxylan with extremely low Ara/Xyl ratio (0.1), with high amounts of ferulic acid monomers and hence very weakly crosslinked. The aleurone layer differed from the outer pericarp by its much lower Ara/Xyl ratio and lower amounts of ferulic acid dimers and trimers. High proportions of ether-linked phenolic acids (released by alkali at 170 °C) were detected specifically in the seed coat and tissues in the crease region. The possible application of biochemical markers found in the various tissues to monitor wheat grain fractionation processes is discussed.  相似文献   

6.
In this study 7 bran fractions were produced by grinding coarse durum wheat bran followed by sieving to achieve median particle size ranges between 115 and 1497 μm. These bran fractions were incorporated into pasta at 1, 5, 10 and 20% and the phytochemical and technological properties evaluated. Higher incorporation of bran, especially at 20%, reduced pasta quality, but a reduced impact was seen at the same degree of incorporation using finer bran. Bran increased antioxidants (by up to 65%), ferulic acid (up to 400%) and phytosterols (up to 130%) in pasta, parameters which were insensitive to bran particle size above 10% incorporation except for ferulic acid, which was higher in particles between 248 and 1497 μm. It is recommended to use finer fractions if bran is added to pasta at 20% and higher, since they provide a better quality pasta while still delivering enhancements in phytochemical content above regular semolina pasta.  相似文献   

7.
The enrichment of liquid food matrix with wheat bran has not yet been explored. This study investigated the impact of disintegrating wheat bran preparations on their stability at high moisture content. Three wheat bran preparations – standard bran, peeled bran and aleurone rich fraction – were modified by dry grinding, enzymatic degradation, wet grinding and microfluidization. The sedimentation of processed preparations was evaluated in water solution and related to their physical structure, solubilized compounds and suspension viscosity. In dry ground preparations mixed in water (5% w/w), most of the particles sedimented already in 5 min. Wet grinding disintegrated the physical structure of bran preparations (d50 = 10–16 μm), causing improvement of particle stability due to reduction of gravitational sedimentation. Enzymatic treatment with xylanase efficiently increased the total solubility of the bran preparations (from 18–24% to 40–50%), but the higher solubility was not related to the better stability of particles. Microfluidization of peeled bran and aleurone increased the viscosity and stability of dispersions. The higher viscosity of the microfluidized dispersions was likely correlated with the better homogenisation of the particles, and also with the modified microstructure of treated bran preparations. Disintegrated wheat bran preparations showed high potential for beverage applications.  相似文献   

8.
The possible use of specific biochemical compounds identified in wheat grains was evaluated for monitoring barley grain tissues during fractionation. First barley grain anatomy was studied through microscopic observation and quantification of the relative proportion of each anatomical part in four distinct barley samples from both hulled and hulless genotypes. As expected from cereal phylogeny and irrespective of the possible presence of hull, common features were observed between barley and wheat grains, but the aleurone layer predominated in the outer layers. The specific location of the compounds identified in wheat was established. Phytic acid was specifically localized in the aleurone layer and alkylresorcinols in the composite layer containing the testa, even if their concentration differed from that observed in wheat grain tissues. Thus, these two markers identified in wheat can be used to monitor the corresponding barley tissues, independent of the presence of hulls. Conversely, phenolic compounds, either ferulic acid trimer or p-coumaric acid, cannot be used to monitor respectively the outer pericarp or the aleurone cell walls in barley grains. p-coumaric acid was identified as an efficient marker of the hull and could be used to distinguish hulled or hulless barley grains and to help monitor the dehulling process.  相似文献   

9.
Two agro-industrial co-products, brewers' spent grain and wheat bran, were fractionated by sequentially extracting with alkali of increasing strength. Over 60% of the brewers' grain biomass was solubilised by these treatments, compared with only 25% for wheat bran. The carbohydrate and phenolic composition of the solubilised fractions were determined, highlighting two compositionally different sets of fractions. In both co-products arabinoxylan was the main polysaccharide released. The degree of arabinose substitution of the extracted arabinoxylan diminished as the alkali strength increased. Insoluble residues contained both cellulose and non-cellulosic polysaccharides. In spent grain, the composition of the arabinoxylan in the residue was similar to that of the starting material. In wheat bran, the residual xylan was very highly substituted with arabinose. Both ferulic acid and three forms of diferulic acid (5,5′, 8-O-4′ and 8,5′) were present in the solubilised material, even after treatment with 4 M KOH. Esterified acetate was also present on polymers solubilised with KOH at concentrations up to 1 M. The more soluble fractions of spent grain represented a heterogeneous aggregation of feruloylated arabinoxylans with a broad molecular mass range, but the fractions extracted with stronger base were separated into low molecular weight moieties, presumably due to cleavage of covalent cross-links. Potential food and non-food uses for the isolated fractions from the cereal co-products are discussed.  相似文献   

10.
Wheat bran is an undervalued by-product of white flour and has great nutritional potential due to its high content in fibres and bioactive compounds. Micronized bran could be used as a food ingredient to improve the nutritional potential of cereal products, or be used as a starting material for other processes (bioactive compound extraction or bran fractionation). The aim of this work was to find a way to efficiently decrease the particle size of bran. The influence of the grinding temperature (ambient or cryogenic grinding) on the granulometric distribution of particles, their composition, and their microstructure was studied, at lab-scale and pilot-scale. It showed that the intrinsic characteristics of bran (glass transition within intermediate layers at −46 °C) had more influence on its grinding behaviour than the type of grinding device used: the particles size distributions obtained after grinding at lab-scale and pilot-scale were very similar. At both scales, the granulometric curves were narrow for cryogenic grinding, while for ambient grinding they were spread over the whole particle size range. Ultrafine particles were obtained in both ambient and cryogenic conditions. Negative temperatures, by increasing the material’s brittleness, favoured a fast fragmentation of bran: one step of cryogenic grinding allowed a median particle size of nearly 50 μm to be reached, whereas three successive steps of ambient grinding were needed for the same result. On the other hand, ambient temperature favoured the dissociation of the different constituent layers of wheat bran, and produced less composite particles than cryogenic grinding.  相似文献   

11.
The objectives of this work were to 1) determine the physical structure of untreated wheat bran and the differences in physical structure between its dissected layers; 2) evaluate how bran hydration affected bran crystallinity and polymer order; and 3) determine how enzymatic treatment of wheat bran affected its physical structure. For the first time, X-ray diffraction (XRD), small angle X-ray scattering (SAXS), solid-state 13C cross-polarization magic-angle spinning nuclear magnetic resonance (13C CP/MAS NMR), and polarized light microscopy with a waveplate were used to study the physical structure of wheat bran and its dissected layers. The XRD and solid-state 13C CP/MAS NMR both confirmed the presence of crystalline cellulose in untreated bran, enzymatically treated bran, and dissected bran layers. The outer pericarp had the highest crystallinity of the dissected bran layers and showed negative birefringence. The aleurone layer was low in cellulose content and completely amorphous, yet the cell walls in the aleurone layer showed strong positive birefringence. The treatment of destarched and deproteinated bran with the Updegraff reagent removed amorphous material, leaving its crystalline cellulose structure intact. Hydration of the outer pericarp increased its crystallinity index and CP/MAS NMR resonance intensity, which indicated a possible increase in polymer order. The SAXS also confirmed that cell wall polymers, possibly aggregated cellulose microfibrils, increased in order as a result of hydration.  相似文献   

12.
Bran is a good source of dietary fibre, phytochemicals, and also protein, but highly insoluble and recalcitrant structure of bran hinders accessibility of these components for gastrointestinal digestion. In the present work, influence of bioprocessing on the microstructure and chemical properties of rye bran and wheat bread fortified with the rye bran were studied. In vitro protein digestibility, and release of short chain fatty acids (SCFA) and ferulic acid in a gut model were studied. Bioprocessing of rye bran was performed with subsequent treatments with cell-wall hydrolysing enzymes (40 °C, 4 h) and yeast fermentation (20 °C, 20 h). Bioprocessing of rye bran resulted in reduced total dietary fibre content, caused mainly by degradation of fructan and β-glucan, and increased soluble fibre content, caused mainly by solubilisation of arabinoxylans. Microscopic analysis revealed degradation of aleurone cell wall structure of the bioprocessed rye bran. Bioprocessing caused release of protein from aleurone cells, assessed as a larger content of soluble protein in bran and a higher hydrolysis rate in vitro. Bioprocessed bran had also faster SCFA formation and ferulic acid release in the colon fermentation in vitro as compared to native bran.  相似文献   

13.
Measurement of biochemical markers allows the quantification of wheat (Triticum spp.) grain tissue proportions in milling fractions. In order to evaluate the ability of extending this methodology to an unknown wheat grain batch, the variability of the markers in the different tissues was assessed on various wheat cultivars. Ferulic acid trimer amounts in the outer pericarp ranged from 0.97 to 1.67 μg mg−1 (dm) with an average value equal to 1.31 μg mg−1 (dm). Alkylresorcinols amounts in a composite layer, including the testa, the inner pericarp and the nucellar epidermis, ranged from 10.5 to 16.7 mg g−1 (dm), with an average value equal to 14.0 mg g−1 (dm). In the aleurone layer, phytic acid amounts ranged from 94.9 to 187.2 mg g−1 (dm) with an average value equal to 152 mg g−1 (dm) whereas, para-coumaric acid ranged from 0.08 to 0.29 μg mg−1 with an average level of 0.18 μg mg−1. In the embryonic axis, wheat germ agglutinin ranged from 879 μg g−1 to 2086 μg g−1 with an average value of 1487 μg g−1. The impact of this variability on tissue proportion determination was evaluated and a strategy to decrease the prediction error was suggested. Percentages of the outer pericarp, intermediate layer (including the testa), aleurone layer and embryonic axis within grains were calculated and their variability discussed.  相似文献   

14.
The dehydrodiferulic acid content of different common and durum wheat grains and milling fractions was determined by an HPLC procedure. The 8-O-4′, 5–8′ benzofuran, 5–8′ and 5-5′ dehydrodimers were identified in all samples studied and occurred in decreasing relative amounts, respectively. Durum wheats were twice as concentrated in dimers as common wheats. An important genetic variation for dehydrodiferulic acid content was shown within durum wheat grains, whereas the agronomic conditions had no effect. There was 10 to 20 times more dehydrodiferulic acids in external layers (aleurone, bran) than in the starchy endosperm of durum wheat grains. The content and composition in dimers of the inner endosperm did not vary according to genotypes and cultivation conditions. The ratio of dehydrodimers to monomers of ferulic acid which represented an index of dimerisation, was 1·6 times higher in the external layers of the grain than in the endosperm. No relation was found, however, between the degree of ferulic acid dimerisation and the milling behaviour of durum wheat grains.  相似文献   

15.
Localization of alkylresorcinols in wheat,rye and barley kernels   总被引：1，自引：0，他引：1  
Cereal alkylresorcinols (AR), a group of phenolic lipids mainly found in the outer parts of wheat and rye kernels, are currently being studied for the possibility to use them as biomarkers for the intake of whole grain wheat and rye foods. In this work, AR were localised in grains by using light microscopy and gas chromatographic analysis of hand-dissected botanical and pearling fractions. GC-analysis of hand-dissected fractions showed that more than 99% of the total AR content was located in an intermediate layer of the caryopsis, including the hyaline layer, testa and inner pericarp. Microscopic examination showed that the outer cuticle of testa/inner cuticle of pericarp was the exact location, and that no AR were found in the endosperm or in the germ, suggesting that AR could be used as a selective marker of testa.  相似文献   

16.
Wheat bran is the main by-product during wheat flour processing. Although wheat bran is rich in the bioactive compounds and antioxidant capacity, it is not widely utilized in its natural state. To improve the antioxidant and nutritional properties of wheat bran, a dominant strain, Enterococcus faecalis M2, was screened from lactic acid bacteria (LAB) isolated from various foods. Following solid state fermentation, the soluble dietary fiber content of wheat bran nearly quadrupled compared to the raw material. Total proportion of phenols, flavonoids, alkylresorcinols, along with the antioxidant capacity and free radical scavenging rate were significantly improved, particularly the ferulic acid content increased by 5.5 times. Additionally, the free amino acid content increased with degradation of wheat bran protein, whereas the level of anti-nutrient phytic acid decreased. The results of this study could provide an effective method for biological modification of wheat bran, which further enhance the health benefit and utilization of bran.  相似文献   

17.
Phytosterols and steryl ferulates are bioactive compounds accumulating in the bran and germ of wheat. However, little is known regarding their localisation and composition in the bran layers of the kernel. The aim of this study was to determine the distribution of phytosterols and steryl ferulates in the wheat grain and in the different layers of bran. The wheat fractions, produced by conventional debranning, aleurone separation and a novel electrostatic process, were analysed for phytosterol contents using GC–FID and for steryl ferulate contents using HPLC–UV. The compounds were identified by GC– and LC–MS. Phytosterols and steryl ferulates were concentrated in the bran layers. The steryl ferulates were accumulated in the intermediate layers, whereas the phytosterols were more evenly distributed in the intermediate layers and aleurone cell contents. The phytosterol composition varied within the wheat kernel, while the steryl ferulate composition was similar in different fractions. Sitosterol and campestanyl ferulate were the main compounds. The highest levels of phytosterols (up to 2117 μg/g) and steryl ferulates (up to 703 μg/g) were found in the pearling, aleurone and certain bran fractions. The phytosterol-rich fractions could be utilised in cereal foods to enhance the intake of health-promoting compounds from natural sources.  相似文献   

18.
The mechanical properties of the combined outer layers from near-isogenic wheats differing by hardness were determined. Results from traction tests showed significant differences between the isogenic lines, outer layers from grains of the soft type showing higher extensibility. Determination of the mechanical properties of the corresponding component tissues revealed significant differences between the isolated tissues from soft or hard wheat grains. It also allowed analysis of their respective contribution to the properties of the combined peripheral tissues using a simulation of their rupture as unseparated tissues. According to the results, if the component layers displayed similar maximum lineic force to rupture, the rupture of combined outer layers occurs when the least extensible individual tissue breaks. The major cell wall biochemical components of the combined outer layers and of their component tissues were analysed. The phenolic acid composition of soft wheat pericarp contained more ferulic acid in either monomeric or polymeric forms than the pericarp from hard wheat. Arabinoxylans in walls of the soft wheat pericarp appeared 1.6 times more cross-linked by ferulic acid dehydrodimers than walls of hard wheat. These differences in arabinoxylan cross-linking may explain the observed differences in pericarp mechanical properties.  相似文献   

19.
Bran (branml) obtained by roller milling of soft (Scipion) and hard (Baroudeur) wheat cultivars was further ball-milled for increasing times and the observed particle size distribution expressed as a dispersion index. Bran (branhi) and aleurone layers were also hand-isolated from the same grains and the pattern of size reduction during ball-milling were compared with branml. Branml and branhi were found to fracture more rapidly than isolated aleurone layers due to the presence of the highly friable pericarp and the possible mechanical constraints due to tissues surrounding the aleurone layer. Previously identified markers of the aleurone layer cell contents (phytates) and cell walls (p-coumaric acid) were used to determine their water extractabilities from ball-milled samples and the state and degree of dissociation of the aleurone layer, either as an isolated tissue or within branml and branhi. The results suggest that ball-milling rapidly induces fractures in walls of cells in the aleurone layer. The partial opening of the cells in the aleurone layer allowed extraction of most (≈70%) of the water-extractable phytates, even though their mean particle size was much larger than the dimensions of the cells. A further increase in extractability of phytates was observed when the particle size was reduced below the aleurone cell dimensions. Although much less soluble, p-coumaric acid followed a similar trend to phytates. The different behaviour of branml and branhi was consistent with a weakening effect of the tissues in the former, probably due to the previous milling process. The bran and aleurone layers from both wheat varieties exhibited a similar behaviour.  相似文献   

20.
Pearl millet was decorticated to obtain a bran rich and endosperm rich fraction. The two fractions were soaked in solutions with varying pH. Pearl millet grains were germinated and steamed followed by decortication to obtain two fractions. It was observed that bran rich fractions contained high concentrations of iron, zinc, polyphenols, phytic acid, fibre and flavonoids. Soaking for short duration of 3 h did not result in major mineral losses but decreased the inhibitory factors which depended on the pH. Alkaline soaking decreased flavonoid content by 62.7% in the endosperm rich fraction, while acidic soaking decreased phytic acid content to the maximum in the bran rich fraction. Combination of treatments like germination and heat decreased the phytate content to the maximum in the endosperm rich fraction. Acidic conditions improved zinc bioaccessibility in the bran rich fraction (35%) and iron bioaccessibility (2.5%) in the endosperm rich fraction. Bran rich fraction from germinated grain also had enhanced bioaccessibility of both the minerals but comparatively lesser when compared to soaking under acidic conditions. Soaking the grain components under slightly less than neutral conditions also decreased some of the inhibitory factors and improved the zinc bioaccessibility to some extent in the bran rich fraction.  相似文献   

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