Sustainable development of active biomaterials based on rice industry byproducts
authors Paulo David Martins Brites
supervisors Cláudia Sofia Cordeiro Nunes; Paula Celeste da Silva Ferreira
thesis type Master's thesis
nationality International
author keywords Rice husks, rice bran, hydrothermal treatment, silica, chitosan, phenolic compounds, biofilms
abstract Bioplastics emerge nowadays as an ecological alternative to replace fossil fuels-based plastics, which have a progressively larger environmental impact. Chitosan has been proposed as an alternative to the production of bioplastics in food packaging due to its antimicrobial and antioxidant characteristics, as well as its film forming capacity. On the other hand, millions of tons of rice industry byproducts, namely rice bran and rice husks are produced yearly. Rice bran is rich in functional compounds, such as gamma-oryzanol with antioxidant and UV light filter characteristics. Rice husks, besides having antioxidant properties from phenolic compounds, are rich in silica. The objective of this work was to develop a sustainable process to produce bioactive materials for food packaging. For that, an extraction methodology combining temperature and pressure and using water as solvent, hydrothermal treatment, was used to extract the valuable compounds from rice byproducts. Different extraction temperatures were tested and, in the case of rice bran, the extract obtained at 220 ºC was chosen, whereas for the rice husks was the one obtained at 200 ºC. These extracts had the greatest extraction yields (37% for bran and 6% for husks), a relatively high concentration of phenolic compounds (0.34 mgGAE/g for bran and 0.16 mgGAE/g for husks), as well as a high concentration of carbohydrates (41% for the bran and 25% for the husks). These aqueous extracts were added to the formulation of the chitosan films with a mass chitosan:extract ratio of 1:0.1 and 1:0.5 for the bran and 1:0.1 for the husks. The films, obtained by solvent casting, were characterized in relation to their antioxidant activity, humidity, solubility, surface hydrophobicity and mechanical properties. The films with the incorporation of rice husks extract presented a higher resistance in acid medium, having a solubility of only 19% (the chitosan film had a solubility of 33%). The mechanical properties of the films were affected by the incorporation of the both extracts, having a decrease in the resistance to the tension and flexibility in the films with the incorporation of the highest bran extract and husks extract in comparison with the control film. On the other hand, the incorporation of extracts did not affect significantly this parameter. All the films with the extract incorporation presented a higher antioxidant activity than the control chitosan film (12.6% higher for the bran extract and 6.5 % higher for the husks extract). The results show that byproducts from rice industry have high potential to be used for biofilms production with interesting characteristics for food packaging, namely as active packaging inhibiting the food products oxidation.
year published 2018