In this paper, chitosan was reacted with monochloroacetic acid under alkaline conditions to prepare carboxymethyl chitosan. A 2(3) full-factorial central composite design was applied to evaluate the effect of molar ratio sodium hydroxide (NaOH)/Chitosan (Ch), time and molar ratio monochloroacetic acid (MCA)/Chitosan (Ch) on the reaction yield and on the characteristics of carboxymethyl chitosan such as average degree of substitution (DS¯) and solubility. An optimization strategy based on response surface methodology was used together with the desirability function approach to optimize this process. The occurrence of carboxymethylation was evidenced by FTIR and (1)H NMR spectroscopy. The optimum conditions for carboxymethylation process were found to be 12.4, 10.6h and 5 for molar ratio sodium hydroxide (NaOH)/Chitosan (Ch), time and molar ratio monochloroacetic acid (MCA)/Chitosan (Ch), respectively. Under these optimal conditions, it was possible to obtain carboxymethyl chitosan with DS¯ of 1.86 and solubility of 99.6%. X-ray diffraction and thermogravimetry analysis showed that crystallinity and thermal stability of derivatives was lower than chitosan and decreased with increase of DS¯.

Cellulose was extracted from brewer's spent grain (BSG) by alkaline and bleaching treatments. The extracted cellulose was used in the preparation of carboxymethyl cellulose (CMC) by reaction with monochloroacetic acid in alkaline medium with the use of a microwave reactor. A full-factorial 2(3) central composite design was applied in order to evaluate how parameters of carboxymethylation process such as reaction time, amount of monochloroacetic acid and reaction temperature affect the average degree of substitution (DS) of the cellulose derivative. An optimization strategy based on response surface methodology has been used for this process. The optimized conditions to yield CMC with the highest DS of 1.46 follow: 5g of monochloroacetic acid per gram of cellulose, reaction time of 7.5min and temperature of 70°C. This work demonstrated the feasibility of a fast and efficient microwave-assisted method to synthesize carboxymethyl cellulose from cellulose isolated of brewer's spent grain.

Blend solutions of poly(ε-caprolactone) (PCL) and N-(2-hydroxy)-propyl-3-trimethylammonium chitosan chloride (QCh) were successfully electrospun. The weight ratio PCL/QCh ranged in the interval 95/5-70/30 while two QCh samples were used, namely QCh1 (DQ¯ = 47.3%; DPv¯ = 2218) and QCh2 (DQ¯ = 71.1%; DPv¯ = 1427). According to the characteristics of QCh derivative and to the QCh content on the resulting PCL/QCh nonwoven, the nanofibers displayed different average diameter (175 nm-415 nm), and the nonwovens exhibited variable porosity (57.0%-81.6%), swelling capacity (175%-425%) and water vapor transmission rate (1600 g m 24 h-2500 g m 24 h). The surface hydrophilicity of nonwovens increases with increasing QCh content, favoring fibroblast (HDFn) adhesion and spreading. Tensile tests revealed that the nonwovens present a good balance between elasticity and strength under both dry and hydrated state. Results indicate that the PCL/QCh electrospun nonwovens are new nanofibers-based biomaterials potentially useful as wound dressings.

A quaternized derivative of chitosan, namely N-(2-hydroxy)-propyl-3-trimethylammonium chitosan chloride (QCh), was synthesized by reacting glycidyltrimethylammonium chloride (GTMAC) and chitosan (Ch) in acid medium under microwave irradiation. Full-factorial 2(3) central composite design and response surface methodology (RSM) were applied to evaluate the effects of molar ratio GTMAC/Ch, reaction time and temperature on the reaction yield, average degree of quaternization (DQ) and intrinsic viscosity ([η]) of QCh. The molar ratio GTMAC/Ch was the most important factor affecting the response variables and RSM results showed that highly substituted QCh (DQ = 71.1%) was produced at high yield (164%) when the reaction was carried out for 30min. at 85°C by using molar ratio GTMAC/Ch 6/1. Results showed that microwave-assisted synthesis is much faster (≤30min.) as compared to conventional reaction procedures (>4h) carried out in similar conditions except for the use of microwave irradiation.

No abstract

The extraction and characterization of avocado starch isolated from seeds (Persea americana Mill) were studied. The starch was extracted by steeping, wet grinding and sedimentation process and calculated its yield. Isolated starch was then characterized for chemical composition, morphology and granules size distribution, X-ray diff raction an mid-infrared spectra, swelling powder and solubility, pasting and thermal properties and clarity and syneresis behavior. The starch yield was 42.2%. The results showed starch granules were predominantly ellipsoidal with an average granule size of 17.83 μm. Exhibited B-type X-ray diff raction pattern with 25.7% of crystallinity, and apparent amylose content of 21.5% with similar mid-infrared spectra to other starches. Onset and peak gelatinization temperatures were 67.6 and 76.0 °C, respectively, and gelatinization enthalpy was 14.9 J/g. Starch suspensions showed peak viscosity at 4421 cP and high retrogradation tendency, which was evidenced by opaque gels and syneresis.

No abstract

AGRADECIMENTOS À Deus, por me permitir ter chegado até aqui, sempre me dando amor e forças para continuar em frente. Ao professor Dr. Sérgio Paulo Campana Filho por todo ensinamento, incentivo, amizade, paciência e por tantas oportunidades ao longo desses quatro anos de doutorado.