ISOSTERIC HEAT, ENTROPY, AND GIBBS FREE ENERGY OF PUMPKIN SEEDS (Cucurbita moschata)

Teixeira, Luciana Pinto; Andrade, Ednilton Tavares de; Devilla, Ivano Alessandro

doi:10.1590/1809-4430-eng.agric.v38n1p97-102/2018

Cited by 8 publications

(10 citation statements)

References 15 publications

(19 reference statements)

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“…With high water activity, there are fewer sites available for the bonds between molecules, implying a lower mobility demand for water molecules (Goneli et al, 2010). Similar behavior was observed by Teixeira, Andrade and Devilla (2018) and Silva et al (2016) studying pumpkin and pepper seeds, respectively. The enthalpy and entropy relationship for the sunflower seeds in the desorption process was adjusted according to a linear regression, with a high coefficient of determination (99.92%) ( Figure 5).…”

Section: Resultssupporting

confidence: 84%

Moisture sorption isotherms of sunflower seeds: Thermodynamic analysis

et al. 2019

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The study of the thermodynamic properties provides the knowledge of the sorbent affinity by the water and the spontaneity of the sorption process, important to design drying equipment and to predict hygroscopic behavior during storage. This work aimed to determine and evaluate isotherms of hygroscopic equilibrium and thermodynamic properties for different equilibrium conditions (water contents and temperatures) in sunflower seeds, using the indirect static method. Sunflower seeds with initial water content of 0.164 (decimal, dry basis - d.b.) were used. Fifteen mathematical models were tested for hygroscopic equilibrium modeling, and the Smith model presented the best fit. It was verified that the thermodynamic properties were influenced by the water content, the integral isosteric desorption heat increased with the decrease of the equilibrium water content, ranging from 1.787 to 2.670 kJ kg-1 to 0.198 to 0.0518 (decimal, d.b.), respectively, the desorption process of the sunflower seeds was controlled by the enthalpy and the Gibbs free energy, which varied from 3.6363 to 200.1730 kJ kg-1, was positive for the temperatures studied, with increase to during the desorption process, proving to be a non-spontaneous process.

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Section: Resultssupporting

confidence: 84%

Moisture sorption isotherms of sunflower seeds: Thermodynamic analysis

et al. 2019

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“…It is observed that reducing the equilibrium moisture content increases the energy required to evaporate the water bound to the biological structure of the product, represented by the values of the integral isosteric desorption heat (Figure 1), as observed for several products (Oliveira et al, 2011;Costa et al, 2015;Teixeira;Andrade;Devilla, 2018;Granella et al, 2019). This fact is related to the increase of the water retention capacity of the product in the lower values of equilibrium moisture content, due to the increase of the concentration of fats, proteins and salts of sodium chloride (Hubinger et al, 2009).…”

Section: Resultsmentioning

confidence: 71%

Thermodynamic properties of moisture desorption isotherms of ryegrass (Lolium multiflorum L.) seeds

et al. 2020

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Studies about the thermodynamic properties of ryegrass seeds are necessary to improve post-harvest processes, relating the factors that affect product quality with the interaction between water and its chemical components. Given the importance of recognizing and understanding the intrinsic behavior of water in ryegrass seeds and providing data for the improvement of industrial drying equipment, this work aimed to calculate and evaluate the thermodynamic properties of moisture desorption of ryegrass seeds as a function of the equilibrium moisture content. Ryegrass seeds with initial moisture content of 10.4 (% d.b.) was used. The equilibrium moisture content of seeds was determined by static-gravimetric method at different temperatures (10, 20, 30, 40, and 50 °C) and water activity values (between 0.10 and 0.90), in three repetitions. The Chung Pfost model presented the best fit to the experimental data. It was observed that the integral isosteric desorption heat increased as the equilibrium moisture content decreased, ranged from 2499.95 to 4241.96 kJ kg-1 in the moisture content range 2.80 to 22.10 (% d.b.). Differential entropy also increased with decreasing equilibrium moisture content, as did Gibbs free energy, being positive for all temperature studied, indicating that ryegrass seeds desorption is a non-spontaneous process. The enthalpy-entropy compensation theory was satisfactorily applied to the sorption phenomenon, being controlled by enthalpy.

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“…Interaction between exposure time and temperature during drying can alter grain characteristics (Teixeira et al, 2018;Ziegler et al, 2017), since substantial variations in moisture content may damage seed structure and viability (Botelho et al, 2015a;Oliveira et al, 2012;Goneli et al, 2011).…”

Section: Resultsmentioning

confidence: 99%

Drying process: effects of temperature on the oil of different sunflower genotypes

Wenneck

Saath

Rezende

et al. 2020

Idesia

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Drying is a critical stage in postharvest grain processing and alters its structural and physiological characteristics, affecting the quality of the final product. This study aimed to assess the effect of drying sunflower achenes on oil content. A randomized block design was used, in a 5 x 4 factorial scheme consisting of four drying treatments (35, 40, 50 and 70 ºC) in a forced-air dryer and one under uncontrolled conditions (drying terrace), with four repetitions. Oil content and acid value were analyzed in oil extracted from the achenes of 13 sunflower genotypes grown under the same conditions, whose moisture content declined from 30 to 8 % (dry basic) under different drying temperatures. Data were analyzed using the Scott-Knott test (p < 0.05). Drying under controlled conditions at high temperatures (50 and 70 ºC) reduced the achene oil content for all the genotypes assessed, with an acid value close to (50 ºC) or above (70 ºC) the maximum legal limit. Uncontrolled drying and controlled low temperatures (35 and 40 ºC) showed no significant variations in oil content or acid value.

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ISOSTERIC HEAT, ENTROPY, AND GIBBS FREE ENERGY OF PUMPKIN SEEDS (Cucurbita moschata)

Cited by 8 publications

References 15 publications

Moisture sorption isotherms of sunflower seeds: Thermodynamic analysis

Moisture sorption isotherms of sunflower seeds: Thermodynamic analysis

Thermodynamic properties of moisture desorption isotherms of ryegrass (Lolium multiflorum L.) seeds

Drying process: effects of temperature on the oil of different sunflower genotypes

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