Novas estratégias para valorização do extrato de tanino

Abstract

In a world looking for low environmental impact products, the correct use of each biological resource is needed. Condensable tannins are present in many natural sources and they are the second most abundant phenolic compound in the Earth, behind only of the lignin. Based on both the worldwide production of this phenolic extract and the increase in the researches to improve the use of raw materials, this doctoral thesis aimed to elaborate new strategies toward the valorization of the tannin extract. Mimosa tannin (Acacia mearnsii De Wild) was first purified to remove carbohydrates and acids to obtain new fractions of the extract. The tannin was fractionated using organic solvents with different polarities in a Soxhlet extraction system with single and sequential processes. After that, wood-plastic composites were made using tannin as a natural compatibilizer to apply the Mimosa industrial tannin into products or new materials. The composites were prepared with polypropylene, pine sawdust and wood fibers through a thermokinetic homogenizer and a hydraulic press. Finally, the tannin was incorporated into the nanocellulose to develop a film for application in active packaging. Cellulose and tannin were mixed with distilled water in a mechanical fibrillation microprocessor, forming a homogeneous gel with nanofibrillated cellulose and tannin. Using a vacuum filtration system, the gel was converted into a film. The main results obtained through specific characterizations of the fractions, composites and films were very positive. Different properties were observed in the fractions, and it was possible to target the material obtained for specific purposes, such as for pharmaceuticals and active packaging (lower molecular weight and higher antioxidant capacity) and adhesives (higher molecular weight). Increases in the storage modulus and in the hydrophobicity were obtained from the incorporation of the tannin into wood-plastic composites, besides a compatibilization to be confirmed by morphological analysis. Finally, the films of nanocellulose and tannin presented high antioxidant properties, which was released from the contact with water. Furthermore, the films showed high mechanical strength and barrier capacity, indicating their for application as active packaging for foods and drugs. Therefore, we believe that the tannin extract can and should be used for the elaboration of higher value-added materials, mainly due to its chemical structure, abundance and sustainable production cycle.