Wheat straw separation

Reversed-phase chromatography is the most popular mode of analytical liquid chromatography for phenolic compounds. In most cases, the reported systems for the separation of phenolics and their glycosides in foods are carried out on reversed-phase chromatography on silica-based Cl8 bonded-phase columns. Occasionally, silica columns bonded with C8 were applied in the analysis of phenolic acid standards and coumarins (7), and C6 columns for the analysis of ferulic acid in wheat straw (8). 

In two studies (Lenz et al, 1987 Schocken et al, 1987) the water-soluble metabolites were separated by HPLC. Schocken et al (1987) separated 21 water-soluble metabolites from wheat straw, none of which amounted to >1.5% of the total residue. Lenz et al (1987) separated 20 water-soluble metabolites from soybean forage and 13 from soybean seed. Two of the five major forage metabolites were shown to be DADK O-glucosides by enzyme hydrolysis with a-glucosidase (DADK was detected). The other three major metabolites were resistant to hydrolysis with HC1. The 15 minor forage metabolites were also resistant to acid hydrolysis. 

Westbred 936 wheat straw, a hard red spring variety, was obtained from Grant 4-D Farms (Rupert, ID). All the straw utilized was produced during the year 2000 cropping season and rebaled and stored as previously described (4). Straw stems utilized for these tests were mechanically separated as previously described (5) during the fall of 2000 and were stored indoors at 21 2°C and 13% moisture until used (all tests were begun by the fall of 2002). The composition of the untreated straw stem fraction, determined as described under Compositional Analyses, is shown in Table 1. 

Despite the variety of sources, all lignocellulosic material is composed primarily of cellulose, hemicellulose and lignin [22], Agricultural wastes such as bagasse, com stover and wheat straw are thus a relatively cheap source of these three biopolymers. The major challenge to using lignocellulosic biomass as a feedstock is the development of cost-effective methods to separate, refine and transform it into chemicals and fuels [20],... 

Control samples of wheat straw oxidized by the standard nitrobenzene method (11) and separated by the scheme illustrated in Figure 1 were also tested by the GC-MS method to confirm the validity of the separation and recovery techniques. 

Straw and Other Crop Residues Crop residues are another source of renewable feedstock that do not find their way into milling processes, especially the residues which are already separated from the crop during or directly after harvesting. For most cereals and oil crops, this Hgnocellulosic biomass is called straw, for example, wheat straw, rice straw, or barley straw. The crop residues of maize are known as corn stover. 

Alemdar and Sain [86] extracted Cellulose nanofibres of wheat straw and soy hulls, by a chemi-mechanical technique. They analysed the morphology and physical properties of the nanofibres by scanning and transmission electron microscopy. The wheat straw nanofibres have diameters in the range of 10-80 nm and lengths of a few thousand nanometres, and the soy hull nanofibres have diameters in the range of 20-120 nm and shorter lengths than the wheat straw nanofibres. Fig. 1.21a and b shows the TEM pictures of the wheat straw and soy hull nanofibres. The image shows the separation of the nanofibres from the micro-sized fibres. The thermal properties of the nanofibres were studied by the TGA technique and found that the... 

Ghatak, H. R. [2008). Spectroscopic comparison of lignin separated by electrolysis and acid precipitation of wheat straw soda black liquor. Ind. Crops Prod., 28,206-212. 

Wheat bran and sodium hydroxide were blended at room temperature in a separate reactor one hour before each experiment. Tlie initial L/S ratio was seven and the mixture was stirred for five minutes. The L/S ratio was increased to ten just before the introduction of the mixture into the twin screw extruder with a Nemo excentric-screw pump. Straw was introduced in the extruder s first section with a screw feeder. Straw was mixed with the alkaline dough in the first zone of the barrel through the neutral pitch element and the reverse-pitch screw element successively. The washing water was injected downstream from this zone, and the mixture was conveyed through the second reverse pitch located just downstream from the filtration module. The filtrate was collected and kept in a cold room before further processing, while the refined cellulosic fibres were gathered at the barrel outlet. 

The twin-screw extruder has proved to be a versatile tool for continuous treatment of vegetable matter, either for food or non-food applications. Trials for the direct alkaline extraction of xylans from wheat bran in a twin-screw extruder were unsuccessful. Bran impregnation with sodium hydroxide in the twin-screw extruder was very efficient, but it was necessaiy to make the separation between the hemicellulosic gel and the lignocellulosic matrix in another apparatus and remained difficult without a dilution to a L/S ratio of 50. Bran and straw co-extrusion was therefore investigated to be able to reduce the L/S ratio. Straw fibres form a dynamic plug in the restrictive elements of the screw profile just after the filtration zone. The pressure induced in the extruder sheath by the cellulosic fibres enabled the liquid/solid separation. 

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