Isotermas de dessorção de pimentão verde e energia envolvida no processo Desorption isotherms of green bell peppers and the energy involved in the process*Autor Correspondente | Corresponding Author Recebido: Out. 01, 2014 Aprovado: Maio 18, 2015 ResumoEste trabalho teve como objetivos a obtenção das isotermas de dessorção do pimentão verde e a avaliação das propriedades termodinâmicas de sorção do fruto. As isotermas foram obtidas em função da temperatura (30°C, 40°C, 50°C e 60°C) em umidades relativas entre 4,0-90,0%. Os dados experimentais foram ajustados aos modelos matemáticos GAB, BET, Halsey, Henderson e Oswin para se descrever seu comportamento. Os resultados demonstram que o modelo de GAB descreveu com maior precisão as isotermas de dessorção do pimentão verde entre as faixas de atividade de água (a w ) selecionadas, em uma temperatura fixa. O calor isostérico de sorção (q st ) pôde ser determinado a partir de dados de sorção de umidade utilizando-se a derivada da equação de Clasius-Clapeyron, obtendo-se então o calor envolvido no processo de dessorção de umidade do pimentão verde fresco. A teoria da compensação entalpia-entropia ou isocinética foi aplicada aos dados experimentais, sugerindo que o processo de dessorção é conduzido pela entalpia. Palavras-chave: Calor isostérico; Secagem; Modelo de GAB; Compensação Entálpica-Entrópica. SummaryThis study aimed to obtain the desorption isotherms of green bell peppers and evaluate the thermodynamic properties of the moisture sorption of the fruit. The isotherms were obtained as a function of temperature (30°C, 40°C, 50°C and 60 °C) between 4.0 and 90.0% of relative humidity. The experimental data were fitted to the GAB, BET, Halsey, Henderson and Oswin mathematical models to describe their behaviour. The results showed that the GAB model described the sorption isotherms of green bell peppers with greater accuracy in the range of water activities (aw) selected, at a fixed temperature. The isosteric sorption heat (qst) could be determined from the moisture sorption data using the derivative of the Clasius-Clapeyron equation, to obtain the heat involved in the desorption process of the moisture of fresh green bell peppers. The enthalpy-entropy compensation or isokinetic theory was applied to the experimental data and suggested that the desorption process was driven by enthalpy.

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In this study, the optimum conditions for the multi‐enzymatic recovery of cellulases produced by Aspergillus niger were investigated using sugarcane bagasse. Two extraction methods were investigated: the two‐stage solid–liquid extraction (SLE) followed by ultrasound‐assisted extraction (UAE), and the single‐stage SLE. The ultrasound effects were evaluated using a Doehlert design, in which the pH (5.0–9.0) and sonication power (0.8–2.0 W ml−1) were independent variables. For the single‐stage SLE, temperature (25–45°C), time (10–60 min), and pH (5.0–9.0) were analyzed using the Box–Behnken design. Both processes were monitored to evaluate FPase, CMCase, and β‐glucosidase (U ml−1) activities. The maximum enzymatic activities (EA) obtained for FPase, CMCase, and β‐glucosidase in the SLE–UAE were 0.352, 0.321, and 1.412 U ml−1, respectively. Unlike in most previous studies, sonication was insignificant (p < 0.05) with respect to the enzymatic complex within the evaluated ranges. Moreover, sonication changed the EA when lower than 1.2 and higher than 1.6 W ml−1, mainly inhibiting the EA of β‐glucosidase. The single‐stage SLE was more effective than the two‐stage SLE–UAE, and the maximum EA values for FPase, CMCase, and β‐glucosidase were 0.354, 0.303, and 3.135 U ml−1, respectively. The single‐stage process was better because it consumed less energy, required simpler equipment, and provided higher efficiency in a shorter time. This study will improve diversified enzyme extraction from sugarcane bagasse, reduce enzyme production costs, and enhance bagasse utilization.