Wheat bran-based biorefinery 2: Valorization of products

Wheat bran is multi-layered and consists of different cell types with different chemical compositions. The relatively high content of protein as well as the small amount of lignin is the key differentiator to other lignocellulose containing biomasses. Following the classical route of a biorefinery, bran may be disintegrated to a high extent and separated into fractions of high purity in order to build up new chemicals which serve as precursors for higher polymerized compounds. Secondly, bran contains substances that are per se valuables, but need to be further separated and purified.     

酶解麦麸产品抗氧化活性研究

采用黑曲霉发酵制备阿魏酸酯酶和阿拉伯木聚糖酶混合酶制剂，利用该酶制剂降解麦麸获得麦麸酶解产物（E—HWB）；通过测定它的DPPH清除能力、还原能力和对亚油酸过氧化的抑制作用，探讨了其抗氧化能力。结果表明，EHWB的抗氧化活性强于Vc及阿魏酸，是一种天然、无毒、高效的天然抗氧化剂。     

The effects of aqueous extraction on the performance of wheat bran in bread

Wheat bran was sieved into coarse, medium and fine fractions prior to extraction with tap water. Bran, bran extract and bran residue were analysed for moisture, protein, fat, ash, pentosan and phytic acid. Farinograph measurements and baking tests showed maximum dough resistance and loaf volume of a white flour were both increased by the addition of the residue. Both these parameters were substantially decreased by bran extract and, to a lesser degree, by the bran itself. These findings were common amongst the size fractions although the residue from the coarse bran had the greatest effect on loaf volume and dough properties.     

Thermogravimetric analysis of water release from wheat flour and wheat bran suspensions

Bran is hygroscopic and competes actively for water with other key components in baked cereal products like starch and gluten. Thermogravimetric analysis (TGA) of flour–water mixtures enriched with bran at different incorporation levels was performed to characterise the release of compartmentalised water. TGA investigations showed that the presence of bran increased compartmentalised water, with the measurement of an increase of total water loss from 58.30 ± 1.93% for flour only systems to 71.80 ± 0.37% in formulations comprising 25% w/w bran. Deconvolution of TGA profiles showed an alteration of the distribution of free and bound water, and its interaction with starch and gluten, within the formulations. TGA profiles showed that water release from bran-enriched flour is a prolonged event with respect to the release from non-enriched flour, which suggests the possibility that bran may interrupt the normal characteristic processes of texture formation that occur in non-enriched products.     

Extraction of protein and solids from wheat bran

The influence of pH, time, temperature, cellulase treatment and washing conditions on the recovery of solids and protein from Australian wheat bran was investigated. Highest yields (83% of available protein, 72% of total solids) were achieved by extracting at pH 12 and washing with water at pH 7. However, acceptable yields could be obtained under near neutral conditions by extracting at pH 6.5 for 16 h followed by three washes at pH7. Under these conditions 72% of the protein and 55% of the total solids were extracted and greater stability of the vitamins thiamin, riboflavin and pyridoxine was expected. The use of cellulase in an attempt to disrupt the aleurone cell walls did not improve the recoveries of either protein or solids.     

Composition and functionality of wheat bran and its application in some cereal food products

Production of wheat bran (WB) for human consumption is estimated to be about 90 million tonnes per year. WB is a cheap and abundant source of dietary fibre which has been linked to improved bowel health and possible prevention of some diseases such as colon cancer. It also contains minerals, vitamins and bioactive compounds such as phenolic acids, arabinoxylans, alkylresorcinol and phytosterols. These compounds have been suggested as an aid in prevention of noncommunicable diseases such as cardiovascular disease. This article discusses WB extraction, its nutritional properties, potential health benefits, effects on quality and sensory properties of some cereal foods, and its application in some baked products as well as in fried cereal snacks, as an additive for oil reduction and fibre enrichment.     

Effect of thermal processing on antioxidant properties of purple wheat bran

Antioxidant activity of purple wheat bran, heat-treated purple wheat bran, and purple wheat bran muffins was evaluated to determine the impact of thermal processing on potential health benefits. The purple wheat bran and muffin samples were analyzed for total phenolic content, anthocyanin content and free radical scavenging activity using peroxyl (oxygen radical absorbance capacity assay) and 2,2-diphenyl-1-picrylhydrazyl (DPPH assay) radicals. Total phenolic content and oxygen radical absorbance capacity (ORAC) values of sample extracts were significantly affected by various extracting solvents. The conditions selected for heat treatment did not markedly change antioxidant activity of purple wheat bran. However, there was a significant reduction in total phenolic contents, ORAC values and total anthocyanins during processing of purple wheat bran- or heat-treated purple wheat bran-enriched muffins. On the contrary, muffin extracts still remained excellent in DPPH radical scavenging activity.     

Some functional properties of oat bran protein concentrate modified by trypsin

Oat bran protein concentrate (OBPC) was prepared from oat bran, and hydrolyzed using trypsin. Protein hydrolysates of three different degrees of hydrolysis (4.1%, 6.4% and 8.3% respectively) were obtained. SDS-PAGE analysis demonstrated that oat globulin was the major protein component in OBPC. After trypsin treatment, acidic polypeptides were partly degraded into large peptides (M_r = 29,000–33,000) and small peptides (M_r < 20,000); however, basic polypeptides were almost intact. The functional properties of the resulting products were compared with those of control OBPC. Marked changes in the protein functionality were caused by proteolysis. The solubility, water-holding capacity, emulsifying activity and foaming ability of the hydrolysates gradually increased with the increase in DH. However, the oil-holding capacity, emulsifying stability and foaming stability of the hydrolysates reduced to a certain extent.     

Protein glycation inhibitory activity of wheat bran feruloyl oligosaccharides

Protein glycation is believed to play an important role in the development of long-term disorders associated with diabetes. Water-soluble feruloyl oligosaccharides (FOs) from wheat bran, the ferulic acid esters of oligosaccharides, have been reported as natural antioxidants. The present work assesses the chelating activity of FOs and their inhibition of protein glycation in a bovine serum albumin (BSA)/glucose system, using fluorescence spectroscopy and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE). FOs exhibited an effective ferrous ion chelating activity, and quenched the fluorescence intensity of glycated BSA in a dose-dependent manner with 64.0% of inhibition at 1.0 mg/ml. Further, the formation of advanced glycation end products in the tested system was significantly decreased by FOs, as shown by SDS–PAGE. These data indicate that FOs might be beneficial as glycation inhibitors under specified conditions.     

Flow characteristics and the water retention properties of wheat bran

A method is described which enables cereal fibre to be categorised by the rate of flow of water when packed into a column. This flow-rate method enables changes in physical characteristics of fibre, predictive of faecal bulking action, to be readily identified. Flow rate through coarse wheat bran was 200 ml h^?1 and 120 ml h^?1 for fine wheat bran. Heating wheat bran (40°C, 70°C) has an irreversible enhancing effect on flow rates. The initial ranking of the brans (coarse greatest, fine least) remains consistent despite changes resulting from cooking. Flow rates are affected by ionic strength of the eluting solutions. A 6 m urea elution reduces the flow rate and this reduction is reversed by eluting with lower ionic strength solutions.     

Calcium modulated activity enhancement and thermal stability study of a cationic peroxidase purified from wheat bran

A cationic form of peroxidase was purified from wheat bran, a major by-product of wheat milling industry to near homogeneity by ammonium sulphate precipitation, anion exchange, and cation exchange and gel filtration chromatography. It was a glycoprotein with a molecular weight of 44 kDa, pH optimum of 4.8 and carbohydrate content of 13.8%. The enzyme showed Ping-Pong Bi Bi type catalysis. Inclusion of calcium during purification increased the specific activity and yield of the enzyme. Activity of purified enzyme was enhanced by calcium more than 400% in a biphasic manner. Purified enzyme exhibited increased thermal stability when calcium was added. There was no change in tryptophan fluorescence by the addition of calcium, but the haem absorption at 403 nm showed a change indicating an alteration in the haem environment. Calcium is essential for maintaining the haem structure, enzymatic activity and thermal stability of wheat bran peroxidase.     

Antioxidant activity of feruloylated oligosaccharides from wheat bran

Ferulic acid, the main phenolic acid in wheat bran, is esterified to arabinose residues in the cell wall arabinoxylan. Treatment of wheat bran insoluble dietary fibre with xylanases from Bacillus subtilis released feruloylated oligosaccharides, which were purified with Amberlite XAD-2. The antioxidant activity of such oligosaccharides was evaluated using the assay system for erythrocyte hemolysis mediated by peroxyl free radicals generated from 2,2^′-azobis-2-amidinopropane dihydrochloride (AAPH) under in vitro conditions. The feruloylated oligosaccharides inhibited hemolysis of erythrocytes in a dose-dependent manner with 91.7% inhibition of erythrocyte hemolysis at 4 mg/ml.     

Wheat bran feruloyl oligosaccharides enhance the antioxidant activity of rat plasma

Wheat bran feruloyl oligosaccharides (FOs) possess in vitro antioxidative potential. The aim of this paper is to investigate the protective effect of FOs against oxidative stress in rat plasma. The levels of oxidative stress markers (oxidised glutathione and malondialdehyde) and the activities of antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) in plasma from rats fed with a standard diet supplemented with 1% FOs were evaluated. The anti-radical capacity of rat plasma after ingestion of 0.5 mg FOs was measured using AAPH as the free radical inducer. Compared to the control group, the antioxidant enzyme activity was higher in plasma from rats fed with FOs, and oxidised glutathione and malondialdehyde levels were lower. Plasmas of rats after ingestion of FOs were more resistant to AAPH-induced hemolysis than was the control group (P < 0.01). These results suggest that FOs enhance the level of antioxidative activity in rat plasma in vivo.     

Enzymatic preparation and functional properties of wheat gluten hydrolysates

The water-insolublity of wheat gluten is one of the major limitations for its more extensive use in food processing. Wheat gluten was enzymatically hydrolyzed by several commercially available proteases (Pancreatin Trypsin 6.0S, Porcine pepsin, Pancreatin and Alcalase 2.4L) with protein recovery varying from 42.5 ± 0.7% to 81.3 ± 0.1%. The hydrolytic efficiency of these proteases on wheat gluten was also compared. Alcalase served best for the preparation of wheat gluten hydrolysates (WGHs). Thus, Alcalase-assisted hydrolysates of wheat gluten (AWGHs) with different degrees of hydrolysis (DH 5.0, 10.0 and 15.0%) were further assessed for their functionalities. All the AWGHs had excellent solubility (>60%) over a pH range of 2–12. The emulsifying and foaming properties of AWGH with relatively low DH (5.0%) were remarkably higher compared to the original gluten. However, extensive hydrolysis of gluten resulted in remarkable reduction in emulsifying and foaming properties.     

Optimisation of ultrasound-assisted extraction of phenolic compounds from wheat bran

Wheat bran, an important by-product of the cereal industry, is rich in potentially health-promoting phenolic compounds. In this paper, the phenolic compounds from wheat bran were extracted by ultrasound-assisted extraction technology. The experiments were carried out according to a five level, three variable central composite rotatable design (CCRD), and the best possible combination of solvent concentration, extraction temperature and extraction time with the application of ultrasound, for maximum extraction of phenolic compounds from wheat bran, was obtained, through response surface methodology (RSM). The optimum extraction conditions were as follows: ethanol concentration, 64%; extraction temperature, 60 °C; and extraction time, 25 min; and the extraction time was the most significant parameter for the process. Under the above-mentioned conditions, the experimental total phenolic content was 3.12 mg gallic acid equivalents/g of wheat bran tested, which is well matched with the predicted content.     

麦麸中四种蛋白的Osborne法提取分离及性能研究

麦麸蛋白是植物蛋白的一种,通过研究麦麸蛋白的组成及性质以应用于食品工业。用Osborne法分离提取出清蛋白、球蛋白、醇溶蛋白和谷蛋白4种蛋白,考马斯亮蓝法测定等电点。实验表明:清蛋白、球蛋白、醇溶蛋白和谷蛋白的相对含量分别是48.06%、25.12%、18.70%,8.12%;等电点依次为4.0、5.0、5.8、5.2。电镜表观发现,清蛋白和球蛋白分子均连接紧密,清蛋白表面细致多层,局部有孔;球蛋白表面疏松,表面孔较少。醇溶蛋白和谷蛋白分子连接松散,醇溶蛋白呈不规则的球状,谷蛋白表面平滑,分子团多。功能性质测定结果表明:四种蛋白中球蛋白的持水性和持油性最大,分别为5.00g/g和2.40g/g;醇溶蛋白的起泡性、起泡稳定性和乳化力最强,分别为376%、71%和75%。因此,球蛋白适宜作为添加剂应用在肉制品中,醇溶蛋白适宜作为添加剂应用在奶制品和蛋糕等食品配方中。      

Effect of bioprocessing of wheat bran in wholemeal wheat breads on the colonic SCFA production in vitro and postprandial plasma concentrations in men

The health benefits of whole grain consumption can be partly attributed to the inclusion of the bran or outer-layers of the grain rich in dietary fibre. Fibre is fermented in the colon, leading to the production of beneficial metabolites, such as short-chain fatty acids (SCFA). The effect of five different types of bread on the SCFA production was studied in an in vitro model of human colon. Additionally, the postprandial effects of two selected breads on the SCFA plasma concentrations were investigated in men. A higher in vitro production of butyrate was induced by wholemeal wheat bread with bioprocessed bran than by native bran. The increase in butyrate seemed to be in exchange for propionate, whilst the total SCFA production remained similar. However, differences between the two breads in the postprandial butyrate concentrations could not be detected in peripheral blood of men, probably due to an effective utilisation by colonocytes.     

Antioxidant properties and components of bran extracts from selected wheat varieties commercially available in Pakistan

Antioxidant activity of bran extracts from five wheat varieties indigenous to Pakistan, i.e. Punjab-96, Bhakkar-2002, Uqab-2000, SH-2002, and Pasban-90, has been evaluated. All the bran extracts exhibited appreciable total phenolic content (2.12-3.37 mg gallic acid equivalent/g bran), total flavonoid content (epicatechin equivalent 262-304 μg/g bran), chelating activity (ethylenediaminetetracetate equivalent 597-716 μg/g bran), 2,2′-diphenyl-1-picrylhydrazyl radical scavenging activity (51-79%), ABTS radical cation scavenging activity (Trolox equivalent 27-36 μmol/g), oxygen radical absorbance capacity (97-123 μmol/g), and total anthocyanin content (30-38 mg/kg bran). Tocopherol (22-26 ppm) and tocotrienol content (59-74 ppm) were determined by RP-HPLC. For confirmation of tocopherol content, polarographic study was conducted, which further authenticated the results (21-25 ppm). All the varieties exhibited appreciable antioxidant potential and significant differences were observed among the varieties in different systems of antioxidant activity evaluation.     

Physicochemical,rheological and sensory properties of Egyptian Kariesh cheese containing wheat bran

The physicochemical, rheological and sensory properties during the storage of Kariesh cheeses made with 0.1, 0.2, 0.3, 0.4 or 0.5 g wheat bran/100 g milk were evaluated at 0, 7 and 15 days. The cheeses with 0.5 g wheat bran/100 g milk had a significantly (P < 0.01) higher yield and moisture content, and lower pH and protein content than the control. No significant differences (P > 0.01) in salt and ash contents were observed among the cheeses studied. Texture profile analysis showed that the rheological characteristics decreased significantly in cheeses made with wheat bran. These results suggested that wheat bran (up to 0.4%) can be used to produce a fibre fortified Kariesh cheese.