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.

R ESU M OO estudo da cinética de secagem é de fundamental importância para a modelagem matemática, a qual tem sido muito usada no projeto e em análise dos processos de transferência de calor e de massa, durante a secagem. Buscou-se, então, avaliar a capacidade de ajuste de nove modelos matemáticos comumente utilizados para descrever o processo de secagem em sementes de crambe (Crambe abyssinica Horts), através de um delineamento inteiramente casualizado com três repetições, em que os tratamentos são constituídos de cinco teores de água (0,11; 0,13; 0,17; 0,25 e 0,28 decimal b.s) e cinco temperaturas do ar de secagem (30; 40; 50; 60 e 70 ºC). Para verificação do ajuste dos modelos estudados fez-se análise de regressão não-linear, pelo método Quasi-Newton. De acordo com os dados obtidos concluise que: o modelo da Aproximação por Difusão é o que melhor se ajusta aos dados de secagem obtidos; o aumento da temperatura de secagem promove maior taxa de remoção da água do produto; o coeficiente de difusão apresenta valores da ordem de 0,18 × 10 -10 e 3,92 × 10 -10 m 2 s -1 e a energia de ativação para a difusão líquida foi da ordem de 4,97 kJ mol Drying kinetics of crambe seedsA B ST R A C T Drying kinetics is fundamental for mathematical and modeling widely used in the project and in the analysis of heat and mass transfer during drying. In this study it was sought to assess the capability of adjustment of nine mathematical models commonly used to describe the seed drying process of Crambe abyssinica Horts. The experimental design was completely randomized, with three replications. The treatments were five water contents (0.11; 0.13; 0.17; 0.25 and 0.28 decimal dry weight) and five drying temperatures (30; 40; 50; 60 and 70 ºC). To determine the adjustment of the studied models a non linear regression analyses was performed according to Quasi-Newton method. According to the data obtained it was concluded that: the diffusion approximation method was the model that best adjusted to the drying data obtained; increases in drying temperature promoted higher rate of moisture removal from the seeds; the diffusion coefficient showed values of 0.19 × 10 -10 and 3.9 × 10 -10 m 2 s -1; the activation energy for liquid diffusion during drying of Crambe abyssinica Horts was about 4.97 kJ mol -1 .

RESUMOObjetivou-se, neste trabalho, determinar e modelar as curvas de secagem da pimenta Cumari do Pará (Capsicum chinense Jacqui), nas temperaturas de 45, 55 e 65 ºC e estimar seu coeficiente de difusão. As pimentas foram coletadas no município de Ceres, GO, e transportadas para UEG -Anápolis, GO; a secagem foi conduzida em secador experimental com controle de temperatura e fluxo de ar de 60 m 3 min -1 m -2; os dados experimentais foram ajustados aos nove modelos matemáticos; as magnitudes do coeficiente de determinação (R . Experimental data were adjusted to nine mathematical models. The magnitude of the coefficient of determination (R 2 ), the mean relative error (P) and the estimated mean error (SE) were used to verify the degree of fit of the models. It was concluded that: a) the behavior of the drying curves of Pará Cumari pepper was similar to most agricultural products; b) the drying time was 4 h; 2 h and 50 min and 1 h and 55 min, respectively, for the drying temperatures of 45, 55 and 65 °C; c) the mathematical model of drying proposed by Midilli et al. (2002) was the best fit to the experimental data; d) values of the diffusion coefficient increased with the increase of the temperature of the drying air, with results between 2.29 10 -11 and 2.57 10 -11 m 2 s -1 .

a b s t r a c tThe objective of the present study was to obtain and model drying curves of filmogenic solutions at the temperatures of 25, 30, 35, 40 and 45 C, consisting of different concentrations of starch and glycerol. The percentage of yam starch influenced the initial moisture content, while the critical moisture content varied as a function of the concentration of starch and temperature applied during drying of the filmogenic solutions. Glycerol concentration did not influence any of the parameters analyzed. Models for the two distinct phases (constant and decreasing drying periods) fit well for all drying temperatures and compositions, with average relative error values less than 10%. The interaction between starch content and temperature influenced the drying rate parameters during the constant period and the diffusion coefficients.

No abstract

No presente trabalho estudou-se o efeito da combinação da velocidade de rotação do parafuso (65,9– 234,1 rpm), da temperatura na terceira zona do barril do extrusor (99,5– 200,1°C) e da formulação de farinha de bagaço de jabuticaba (11,59–28,41%), utilizada como fonte de fibra, nas propriedades de pasta de farinhas mistas pré-gelatinizadas de arroz polido e bagaço de jabuticaba. Foram determinadas a fibra detergente ácido (FDA) e a fibra detergente neutro (FDN) das farinhas cruas e suas misturas. As propriedades de pasta foram determinadas em Analisador Rápido de Viscosidade (RVA). A farinha de bagaço de jabuticaba (FBJ) apresentou altos valores de FDA (21,91%) e de FDN (45,47%) o que contribuiu para aumentar o teor de fibra alimentar das misturas extrusadas (FME). As amostras estudadas apresentaram perfis diferentes de viscosidade de pasta com valores mínimos para FBJ, valores máximos para FAP e valores intermediários para FME. A viscosidade inicial a 25°C foi fortemente influenciada pela formulação e pela velocidade de rotação do parafuso, seguidas pela temperatura. A viscosidade máxima a 95°C (VMAX) e a viscosidade final (VFINAL) foram intensamente influenciadas pela formulação e temperatura, seguidas pela velocidade de rotação do parafuso. Ambas aumentaram com a elevação da temperatura e diminuíram com o incremento da porcentagem de FBJ na mistura, bem como pelo aumento da velocidade de rotação do parafuso.

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.