ISOTERMAS DE DESSORÇÃO, SECAGEM E CARACTERIZAÇÃO NUTRICIONAL DAS AMÊNDOAS DAS CASTANHA-DO-BRASIL DA REGIÃO AMAZÔNICA

Abstract

Brazil nut almonds are rich in essential nutrients and can be consumed fresh or processed. The main process applied to this product is drying, so it is possible that physical and nutritional changes can occur with the time and degree of temperature applied. Brazil nuts can be marketed with or without processing, and processed almonds need information on the safe moisture content for storing it at different temperatures. Thus, the objective was to evaluate the influence of different drying temperatures on Brazil nuts (Bertholletia excelsa H. B. K.) physical-chemical characteristic, as well as to determine the product's desorption isotherms. The fruits were collected in the Manaus city and the experiment was carried out in the Vegetable product Post-Harvest Lab of Goiano Federal Institute – Rio Verde Campus. Initially, almonds with an initial moisture content of 19.6% wet basis (w.b.) were subjected to the drying process to a moisture content of 5.0 ± 0.8% (w.b.). The almonds drying was carried out in an oven with forced air ventilation at temperatures of 40, 50, 60, 70 and 80ºC, the drying process was followed by the gravimetric method. After drying, the proximal composition and physical-chemical quality of the almonds processed at different drying temperatures were evaluated. The desorption isotherms were obtained by the static-indirect method, at temperatures of 10, 20, 30 and 40 ºC, with moisture contents varying between 13.00 and 1.60 ± 0.08% dry basis. Brazil nuts collected in the Amazon region were used, the almonds were extracted and processed in the thickness of 0.5 mm to 2.0 cm. The mathematical models commonly used in the literature were adjusted to the experimental data. The drying temperature influenced the nutritional and physical-chemical quality of Brazil nuts. Almonds processed at a temperature of 60°C showed better parameters in proximal and physical-chemical composition. It appears that for macrominerals and microminerals contents there was no direct influence of the treatments, except for the levels of phosphorus and iron. It was observed that the relationship between water activity and moisture content of processed Brazil nuts and storage temperature are directly proportional. The Modified Halsey, Harkins, Sigma Copace, Modified Oswin and Modified GAB models can be used to represent the isotherms of processed Brazil nut almonds. The Sigma Copace model presents the best fit and was used to describe the isotherms. The safe moisture content limits for storing processed Brazil nuts are 5.29; 5.14; 5.00 and 4.87% (w.b.). for temperatures of 10, 20, 30 and 40ºC, respectively.