Anais do Simpósio Latino Americano de Ciências de Alimentos
Anais do 14 SLACA - Simpósio Latino Americano de Ciência de Alimentos

The use of industrial food residues is an attractive way for industries to incorporate the concept of circular economy, more than a market trend, it is a global need, and can be classified as eco-innovations for the food market. For commercialization and application, stability during short to medium storage periods should be investigated. In this context, the present work presents a survey of the thermodynamic properties of grape and blueberry residues in the temperature ranges of 20, 30 and 40 °C, calculated through the monolayer moisture. Static gravimetric method was used to determine equilibrium moisture. One gram samples of dry residues, with an average humidity of 0,10 kg/kg, were placed in glass jars (height of 7 cm and diameter of 6 cm), sealed, with sulfuric acid solutions at concentrations between 0,20 at 0,70 kg/kg (to obtain water activity from 0,043 to 0,878). The experimental data were then fitted to the Guggenheim-Anderson-de Boer (GAB) model. The monolayer moisture values were found in a range of 0,053 to 0,039 kg water/kg dry solid, varying the temperature from 20 to 40 °C. The adsorption surface area decreased with increasing temperature, being very similar, where the grape residue was from 188,54 to 140,91 m2/g and the blueberry residue was from 180,73 to 144,26 m2/g. The differential enthalpy, and consequently the total heat of sorption, showed a strong relationship with the moisture content, reaching values close to 90 kJ/mol at low moisture contents. Negative entropy values, which decreased with increasing moisture content, were observed. The compensation theory can be successfully applied to the moisture adsorption behavior of the residues, indicating that the process was controlled by enthalpy, being it spontaneous.