Abstract
ABSTRACT The objective of this study was to determine the desorption isotherms of 'cajuzinho-do-cerrado' achenes (Anacardium humile St. Hil.) in various conditions of temperature and water activity, as well as to select the one that best represents the phenomenon and to determine the isosteric heat of desorption. The fruits were collected at the Emas National Park, in the municipality of Mineiros-GO, Brazil, pulped and then subjected to drying in silica gel at temperature of 25 ± 2 °C until the moisture contents of 17.6, 13.6, 11.1, 8.7 and 5.3 (d.b.%). After drying, the desorption isotherms were determined by the indirect static method. The water activity (Aw) was determined at different temperatures, and the achenes were placed in a B.O.D. chamber, regulated at 10, 20, 30 and 40 °C. Data of hygroscopic equilibrium moisture content were fitted to different mathematical models through non-linear regression analysis, using the Gauss-Newton method. The Copace model was the one that best represented the hygroscopicity of 'cajuzinho-do-cerrado' achenes, while the integral isosteric heat of desorption of 'cajuzinho-do-cerrado' achenes for the moisture content range of 4.51 to 13.40 (% d.b.) varied from 2,734.82 to 2,548.49 kJ kg-1.
Highlights
The storage of seeds constitutes an important strategy for ex-situ genetic conservation of vegetal species, achieving goals such as plant breeding or propagation
The conditions of relative air humidity and temperature during the storage and the seeds reaching the specific hygroscopic equilibrium will determine the maintenance of their physiological quality for longer or shorter time (Borges et al, 2009)
Hygroscopicity refers to the affinity to the water, i.e., the hydrophilous behavior of some substances in relation to the water
Summary
The storage of seeds constitutes an important strategy for ex-situ genetic conservation of vegetal species, achieving goals such as plant breeding or propagation. The conditions of relative air humidity and temperature during the storage and the seeds reaching the specific hygroscopic equilibrium will determine the maintenance of their physiological quality for longer or shorter time (Borges et al, 2009). Isotherms are obtained through mathematical equations that correlate the moisture content of the product and the relative equilibrium moisture content as a function of a specific temperature (Corrêa et al, 2005b). It is essential the study on water activity, which describes the relationship between the amount of water sorbed by the product, the relative humidity and the temperature (Silva et al, 2007). The tendency of the product to absorb water from the environment determines its hygroscopicity, which is the fundamental quality parameter of agricultural products (Tocon et al, 2009)
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