Abstract
ABSTRACT To maintain seed and soil quality of pumpkin, energy knowledge associated with processing and storage stages is strategic for the optimization of the thermodynamic processes needed for product stabilization. Thus, the objective of this study was to determine isosteric heat, differential entropy, and Gibbs free energy within a temperature range from 20 to 70° C, and relative air humidity levels between 10.75 and 85.11%. The study was based on empirical data for water activity determination. As a result, we verified that as moisture content decreased, the integral isosteric heat of the product increased from 2502.35 to 6231.17 kJ kg-1, differential entropy raised from 1.18 to 12.43 kJ kg-1 K-1, and Gibbs free energy ranged from -243.84 to -432.59 kJ kg-1. Thus, we concluded that the lower the water availability in seeds, the greater the energetic requirement for its removal, as there is a major interaction between water and the product (seeds), indicating an increasingly less spontaneous desorption process.
Highlights
We concluded that the lower the water availability in seeds, the greater the energetic requirement for its removal, as there is a major interaction between water and the product, indicating an increasingly less spontaneous desorption process
From pumpkin (Cucurbita moschata), both the fruit and its grains are consumed, which can be used roasted or as raw material for oil production liable to be utilized in food and energy (Adams et al, 2012; Veronezi & Jorge, 2012; Schinas et al, 2009)
Based on water activity data, the liquid isosteric heat of sorption was determined from the angular coefficients of curves according to ln x (Tabs-1), shown in Figure 1, for different equilibrium moisture contents, as indicated by [eq (3)]
Summary
From pumpkin (Cucurbita moschata), both the fruit and its grains are consumed, which can be used roasted or as raw material for oil production liable to be utilized in food and energy (Adams et al, 2012; Veronezi & Jorge, 2012; Schinas et al, 2009). After removed from the fruit, these grains, which present germinative characteristics influenced by their moisture content alteration (Bee & Barros, 1999), when exposed to the environment can suffer deterioration due to microorganisms attack and enzymatic modifications. For this reason, the proper application of techniques and processes capable of controlling moisture content is essential to ensure maintenance stability of product quality. According to Thys et al (2010), data on product hygroscopic characteristics are used to determine these thermodynamic properties
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