Synthesis and conservation of cellulose nanocrystals.

This work deals with the preparation of cellulose nanocrystals (CNC) from microcrystalline cellulose by acid hydrolysis, discusses how their characteristics varied according to the drying technique used for their conservation and analyzes their re-dispersion in water. A stable water dispersion of "rod" or "needle" type CNC (≈5 nm of diameter, 276 nm of length and 41 mV of Z potencial) was initially prepared and then dried by lyophilization and spray. Thus powders with similar cristalinity but different morphology were obtained, while CNC seemed to aggregate in such an extent that hindered their re-dispersion in water. Only lyophilized CNC could be re-dispersed in water and maintained stable in dispersion for at least 24 h, when working with concentrations of CNC higher than a certain minimum value (3 %) and after submitting them to intense ultrasound treatments. The tested time achieved should be enough to allow their subsequent use in several applications.

An Experimental Validated Computational Method for pKa Determination of Substituted 1,2-Dihydroxybenzenes.

1,2-dihydroxybenzenes (DHBs) are organic compounds which are widely studied as they are applied to advanced oxidation processes (AOPs). These compounds are also related to the development of oxidative stress, wood biodegradation, and neuronal disease in humans. DHBs are metal ligands with pro-oxidant and antioxidant properties. These activities are related to their chelation properties and a consequence of the deprotonation of their hydroxyl groups. In literature, there are several pKa values for the hydroxyl groups of DHBs. These values vary depending on the experimental conditions or the algorithm used for calculation. In this work, an experimentally validated computational method was implemented in aqueous solution for pKa determination of 24 DHBs. The deprotonation order of the hydroxyl groups in DHB was determined observing a selective deprotonation, which depended on the ability of the substituent to donate or withdraw electron density over the ring.

Development of naturally activated edible films with antioxidant properties prepared from red seaweed Porphyra columbina biopolymers.

The aim of this work was to study the physicochemical and antioxidant properties of phycobiliproteins-phycocolloids-based films, obtained from mixtures of two aqueous fractions extracted from Porphyra columbina red seaweed, one enriched in phycocolloids (PcF) and the other in phycobiliproteins (PF). Films with different ratios of PF:PcF (0, 25, 50, 75, 100% [w/w]) and without plasticizer addition were prepared by casting. PcF films had excellent mechanical properties (tensile strength ∼50MPa, elongation at break ∼3% and an elastic modulus ∼17.5MPa). The addition of PF to formulations exerted a plasticizing effect on the PcF matrix, which was manifested in moisture content, water solubility and mechanical properties of the resulting films but not in its water vapour permeability. The antioxidant capacity (TEAC) of the PcF films was significantly increased by the addition of PF and a direct relationship between TEAC and the total phenolic compounds (r(2)=0.9998) and R-phycoerythrin (r(2)=0.9942) was observed.