Determinação do calor específico de polpas de frutas das regiões centro e norte do Brasil

Abstract

In terms of diversity, Brazil is one of the richest countries in the world, and has the largest biomes in Latin America, the Amazon, and the Cerrado. These biomes are rich in renewable natural resources, with emphasis on species of native and exotic fruits, which have unique characteristics and are greatly appreciated. Some fruits like: Açai (Euterpe oleracea Mart.), Acerola (Malpighia emarginata DC), Buriti (Mauritia flexuosa L.), Cajá (Spondias lutea L.), Cashew (Anacardium occidentale L.), Cupuassu (Theobroma grandiflorum) and Tamarind (Tamarindus indica L.) are widely accepted and distributed in the national market. These fruits are not available throughout the year, and, for their conservation and to extend their shelf life through processing, in most cases they require transformations that imply heat transfer and, therefore, the knowledge of thermophysical properties is needed. For this reason, the purpose of this work was to determine the specific heat of these fruits. In order to do so, an adiabatic calorimeter was constructed by using a thermic bottle with a heating system and a temperature sensor, which works based on the Joule effect. Subsequently, the calorific capacity of the system was determined and measurements were made for some substances with known specific heat for comparison: water, acetone and ethyl alcohol. The specific heat values of water, acetone and ethyl alcohol found were 1.06, 0.52 and 0.66 cal / g ° C, respectively. After this, experiments with fruit pulps were carried out. The specific heat ranges found were 0.45 e 0.92 cal/g °C for açai and acerola, respectively. For other fruits, the values found were 0.81, 0.78, 0.51, 0.63 and 0.64 cal/g °C for Buriti, Cajá, Cashew, Cupuassu and Tamarind, respectively. In addition, some physicochemical properties such as moisture content (%), soluble solids (° Brix) and pH were determined. Moisture ranged from 72 to 92%, soluble solids from 3.2 to 21.1 ° Brix and pH from 3 to 5.41. Results obtained for the specific heat will be useful for processing and preserving the pulp of these fruits.