Browsing by Subject "rice bran"

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  • Kortekangas, Anni (Helsingin yliopisto, 2018)
    The literature review focused on acid- and heat-induced protein gelation and the value of rice bran as a food ingredient. A protein-enriched rice bran fraction containing 24% protein, 24% fibre and 22% phytate was used in the experimental work. The aim was to investigate the effect of phytate on protein solubility and study the gelling ability and the effect of a phytate-degrading enzyme, phytase, and a crosslinking enzyme, transglutaminase, in heat- and acid-induced gelation. Phytase treatment of the protein-enriched rice bran fraction decreased the phytate content to 1%. As a result, protein solubility increased at pH 2 from 40 to 55% and at pH 4 from 40 to 47%. In addition, phytase treatment improved gel strength from 1100 to 8200 Pa and water holding capacity from 54.6% to 77.7% of heat-induced gels at pH 8. Acid-induced gelation resulted in low gel strength of 108–190 Pa and water holding capacity of 52.8–56.6%. Transglutaminase had limited crosslinking ability on the protein-enriched rice bran fraction and consequently acid induced gelation and final gel characteristics were not affected by transglutaminase treatment. Acid-induced gels showed fine and homogeneous microstructure, whereas heat induced gelation led to more dense protein and fibre network structure. Based on these results, the protein-enriched rice bran fraction has gelling ability upon heating and acidification. Phytase treatment had great technological potential in altering the protein solubility and heat-induced gelation ability of the fraction.
  • Autio, Tuomo (Helsingfors universitet, 2017)
    Cereal side streams, such as rice bran and dried distiller´s grain with solubles (DDGS) are formed in large quantities in industrial processes. These side streams contain considerable amounts of protein that could be better valorized. Deep eutectic solvents (DES) have been applied in various biomass fractionation studies and could be potentially used as protein extraction solvents. The literature review of this master´s thesis covered the characteristics of rice bran and DDGS, existing extraction methods and DESs. The aim of this work was to study the effect of water content of two DESs (choline chloride:urea, molar ratio 1:2 and sodium acetate:urea, 1:2) on the protein extraction from rice bran and DDGS. Protein extraction yield, protein content in dialyzed and freeze-dried extracts and protein fragmentation were studied. DDGS protein extraction yields with ChCl:urea at 30-50% water contents (56-57%) were significantly higher (p<0.05) than by NaOH (46%) and water (36%), which were used as reference solvents. With NaAcO:urea the water content did not affect the yields significantly and the yields did not differ from those of the reference solvents. In case of rice bran, a low water content produced higher yields and with NaAcO:urea at a water content of 10% the yield was 70%, which was significantly higher than with the reference solvents. Protein contents were measured by two methods, which gave conflicting results. According to BCA assay, the highest protein concentration from DDGS was obtained with NaOH, but according to elemental analysis with the DESs. In case of rice bran, the protein concentrations were extremely low with both methods. Based on these results, rice bran protein extraction using DESs does not appear feasible, whereas DDGS protein could be extracted more efficiently using the DESs than the reference solvents. Neither of the DESs at any water contents degraded protein to a significant extent.