Rice bran stabilization and rice bran oil extraction using ohmic heating

Ohmic heating has been shown to increase the extraction yields of sucrose from sugar beets, apple juice from apples, beet dye from beet root, and soymilk from soybeans. Rice bran is a byproduct of the rice milling process that has economic potential by virtue of highly nutritious rice bran oil contained within the bran. In this study, ohmic heating was used to stabilize rice bran and to improve rice bran oil extraction yield as compared to microwave heating and a control (no heating). Results showed that ohmic heating is an effective method for rice bran stabilization with moisture addition. Free fatty acid concentration increased more slowly than the control for raw bran samples subjected to ohmic heating with no corresponding temperature rise, indicating that electricity has a non-thermal effect on lipase activity. Ohmic heating increased the total percent of lipids extracted from rice bran to a maximum of 92%, while 53% of total lipids were extracted from the control samples. Lowering the frequency of alternating current significantly increased the amount of oil extracted, probably due to electroporation. Ohmic heating was successfully applied to rice bran despite its high oil content. This could have important implications for the enhanced extraction of non-polar constituents.     

Structural features of rice bran hemicellulose

Rice bran hemicellulose was fractionated by ammonium sulphate precipitation, ion-exchange chromatography and enzymatic techniques. Methylation analysis of each fraction revealed that the bran hemicellulose consisted mainly of highly branched arabinoxylan and xyloglucan. The acidic arabinoxylan main component appeared to have more doubly-branched xylose residues in the main chain and also more complicated side chains than the endosperm arabinoxylan. Xyloglucan was also isolated from the crude hemicellulose but the amount of β-(1 → 3), (1 → 4)-glucan was very small compared to the endosperm hemicellulose.     

Hydrolysis of wheat bran,rice bran and jute powder by immobilized enzymes from Macrophomina phaseolina

The stability of cellulolytic and hemicellulolytic enzymes from Macrophomina phaseolina improved on immobilization and was 1.5 to 2-fold more active against pre-treated wheat bran, rice bran or jute powder. The hydrolysis efficiency of the catalyst increased with a decrease in its particle size. About 80% (w/v) of the sugar obtained from wheat bran was assimilated by Saccharomyces sp., whereas the corresponding values for rice bran and jute powder were about 70 and 50% (w/v), respectively.     

Monoclonal antibodies against rice bran lectin.

Two mouse monoclonal antibodies (IgM) were produced against the N-acetylglucosamine-specific rice bran lectin. It was difficult to establish antibody-producing hybrids when soluble rice lectin was used for immunization. Therefore a complex of rice lectin and chitin, a water-insoluble polymer of N-acetylglucosamine, was used as immunogen. Antibody reactivity against Gramineae lectins from barley, rice, rye and wheat (wheat germ agglutinin) was tested in ELISA and two (137,E-1 and 140,B-3) were found to be specific for rice lectin. Gramineae lectins were separated by sodium dodecyl-sulphate-polyacrylamide gel electrophoresis and electroblotted to nitrocellulose papers. Analyses showed that the antibodies reacted strongly with non-reduced rice lectin, whereas only weak staining was seen with the other lectins. The binding was abolished after treatment with 2-mercaptoethanol suggesting that disulphide bond tertiary structures were necessary for epitope integrity.     

Adsorption of mutagens by refined corn bran

Refined corn bran (RCB), a dietary fiber derived from the mechanical refining of corn hulls, effectively adsorbed various environmental mutagens. When RCB was added at a concentration of 10 mg/ml to an aqueous solution of dinitropyrene (DNP), 91.6% of the mutagenicity towards Salmonella tester strain TA98 disappeared. Under similar conditions decreases in mutagenicity of DNP using wheat bran and cellulose powder were 58.4% and 43.0%, respectively. The adsorption of DNP to the fibers appeared irreversible since little mutagenicity was recovered by washing the treated fibers with aqueous buffer solutions of various pHs. Even with an organic solvent (methanol: ammonium hydroxide 50:1), only 2/3 of the mutagenicity of DNP was recovered. RCB could similarly adsorb mutagenic heterocyclic amines such as IQ, Trp-P-1, Trp-P-2, Glu-P-1, and Glu-P-2.     

Cell wall polysaccharide interactions in maize bran

Sequential extractions with alkali have been carried out in order to study the nature of linkages which hold heteroxylans in maize bran cell walls. Treatment with 0.5 sodium hydroxide at 30 °C for 2 h released all the phenolic acids (p-coumaric, ferulic, and diferulic) but extracted only ˜30% of heteroxylans (S₁); further treatment with 1.5 potassium hydroxide at 100 °C for 2 h released the remaining heteroxylans (S₂). The heteroxylans from S₁ and S₂ had a similar neutral sugar composition and structure, but their weight average molecular weights were 270 kDa (M_w/M_n = 2) and 370 kDa (M_w/M_n = 2.8), respectively. Proteins (5%) are found with polysaccharides from S₁ and S₂, with different amino acid composition. The results suggest that covalent linkages through phenolic acids are only partly responsible for the associations of maize bran heteroxylans in the cell wall and that linkages to structural cell wall proteins were probably the main cause of heteroxylan insolubility.     

Fractionation of the rice bran layer and quantification of vitamin E, oryzanol, protein, and rice bran saccharide

Value-added processing with respect to rice milling has traditionally treated the rice bran layer as a homogenous material that contains significant concentrations of high-value components of interest for pharmaceutical and nutraceutical applications. Investigators have shown that high-value components in the rice bran layer vary from differences in kernel-thickness, bran fraction, rice variety, and environmental conditions during the growing season. The objectives of this study were to quantify the amount of rice bran removed at pre-selected milling times and to correlate the amount of rice bran removed at each milling time with the concentration of vitamin E, gamma-oryzanol, rice bran saccharide, and protein obtained. The ultimate goal of this research is to show that rice bran fractionation is a useful method to obtain targeted, nutrient-rich bran samples for value-added processing. Two long grain rice cultivars, Cheniere and Cypress, were milled at discrete times between 3 and 40 seconds using a McGill mill to obtain bran samples for analysis. Results showed that the highest oryzanol and protein concentrations were found in the outer portion of the rice bran layer, while the highest rice bran saccharide concentration was found in the inner portion of the bran layer. Vitamin E concentration showed no significant difference across the bran layer within a variety, though the highest magnitude of concentration occurs within the first 10 seconds of milling for both varieties. To extract the higher concentration of oryzanol and protein only the outer portion of the bran layer requires processing, while to extract the higher concentration of rice bran saccharide, only the inner portion of the bran layer requires processing. Rice bran fractionation allows for the selective use of portions of the bran layer and is advantageous for two reasons: (1) bran fractions contain higher concentrations of components of interest with respect to the overall bran layer average, and (2) less bran needs to be processed to obtain components of interest.     

枯草杆菌碱性蛋白酶水解玉米皮蛋白

以枯草杆菌碱性蛋白酶对玉米皮进行水解,制取玉米蛋白水解液,结果,该酶水解的最佳工艺条件为：在浓度5％的玉米皮中加2．67％酶制剂,pH7.5,55度反应1h,制得的蛋白水解液中,蛋白质溶出率为89．3％,水解度为9．0％。     

An ecofriendly approach to process rice bran for high quality rice bran oil using supercritical carbon dioxide for nutraceutical applications

An integrated approach to extraction and refining of RBO using supercritical carbon dioxide (SC-CO2) in order to preserve the nutritionally important phytochemicals is reported here. Process variables such as pressure, temperature, time, solvent flow rate and packing material on extraction yield and quality of RBO were investigated using a pilot model SC-CO2 extraction system. Three isobaric (350, 425 and 500 bar), three isothermal temperatures (50, 60 and 70 degrees C), three extraction times (0.5, 1 and 1.5h), at 40/min CO2 flow rate and three packing materials (pebbles, glass beads and structured SS rings) were employed. The RBO yield with SC-CO2 extraction increased with temperature and time under isobaric conditions. At the 60 degrees C isotherm, an increase in the RBO yield was obtained with an increase in the pressure and time. The RBO yield increased significantly with structured SS rings used as packing material. The RBO extracted with SC-CO2 had negligible phosphatides, wax and prooxidant metals (Fe and Cu) and was far superior in color quality when compared with RBO extracted with hexane. At the optimum condition of extraction at 500 bar, 60 degrees C for 1.5h, with structured SS rings used as packing material, the yield of RBO was comparable with that of hexane extraction (22.5%). The phytochemical contents of the RBO under the optimum conditions were in the range of tocols, 1500-1800 ppm; sterols, 15,350-19,120 ppm and oryzanol 5800-11,110 ppm.     

Isolation of oryzanol from crude rice bran oil

The isolation of oryzanol from crude rice bran oil (RBO) was achieved by a two-step crystallization process. In the first crystallization, oryzanol was concentrated in the liquid phase along with free fatty acid (FFA), monoacylglycerol (MG), squalene, tocols, and phytosterols, whereas the solid phase contained mainly triacylglycerol (TG) and steryl esters. Oryzanol-rich product obtained from the first crystallization was subjected to the second crystallization where the oryzanol-rich product was kept at room temperature (20.5+/-1.5 degrees C) for 24h. Hexane was added as anti-solvent to the oryzanol-rich product and kept at 5+/-1 degrees C for another 48h. Parameters that affect the isolation of oryzanol from crude RBO were systematically investigated. Under optimal operation conditions, oryzanol with purity and recovery of 93-95% and 59%, respectively, was obtained from RBO with an initial FFA content of ca. 5%.