05), on other hand, temperature increase caused an increase in molecular weight and powder darkening ( Table 2). The temperature increase found powder with lower final moisture content and increased outlet air drying temperature, thus chitosan polymerization occurred due to bonding of chitosan chains and consequently TSA HDAC chemical structure the powder darkening. This shows that inlet air drying temperatures of 100 °C and 110 °C cause alterations in chitosan characteristics. Similar behavior was obtained by Srinivasa et al. (2004) in drying of chitosan films in different conditions, they showed that temperature increase from 80 °C to 100 °C caused darkening in chitosan films,
and attributed this behavior to Maillard reaction. Wachiraphansakul and Devahastin (2007) in spouted bed drying of okara showed that the temperature increase caused darkening in the powder, increasing oxidation level and decreasing the protein solubility. Therefore, the best operation condition ABT-199 supplier in spouted bed for chitosan drying was with inlet air drying temperature of 90 °C in a slot-rectangular spouted bed. In this condition, polymerization and darkening
of chitosan powder does not occur. In addition, fine powder with commercial moisture content, deacetylation degree 85% and faint yellow coloration was obtained. Chitosan powder with these characteristics can be used in dye adsorption (Piccin et al., 2009), edible films (Aider, 2010) and membranes (Torres, Aimoli, Beppu, & Frejlich, 2005). Chitosan powder obtained in the best drying condition was characterized according TG and DTG curves, FT-IR analysis and SEM. Fig. 2 shows TG and DTG curves of chitosan powder. To determine the temperature PAK5 ranges in relation to hydration percentages, organic material decomposition and
waste, DTG curves were used, related to the first differentiate thermogravimetric curve (Cestari, Vieira, Santos, Mota, & Almeida, 2004). TG and DTG demonstrate that under an atmosphere modified by N2 (Fig. 2) chitosan mass loss occurred in three steps. The first mass loss step, from about 25 °C to 175 °C concerns the loss of water, which is adsorbed both on the surface and in the pores of the chitosan (Cestari et al., 2004). The decomposition of the chitosan is observed from about 175 °C to 400 °C. A carbonization of material was observed at 400 °C. Thus chitosan powder obtained in spouted bed had high thermal stability. Fig. 3 shows FT-IR analysis of chitosan powder. In Fig. 3 chitosan characteristics peaks can be observed. A strong band in 1556 cm−1 shows a typical chitosan amino group (–NH2). In 1640 cm−1 an axial deformation of C O (amide band I) can be observed. The weak bands in 1020 cm−1 and 1080 cm−1 are related to C–N links, and in 2933 cm−1 primary amine stretching can be observed. These peaks are involved with functional chitosan amino group. In addition, in 3470 cm−1, hydroxyl groups linked in chitosan structure can be observed.