Effect of temperature on moisture desorption isotherms of kheer

Kumar, Anil; Singh, Ravinder; Patil, G. R.; Patel, A. A.

doi:10.1016/j.lwt.2003.10.009

Cited by 49 publications

(23 citation statements)

References 28 publications

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“…In drying processes the lower the activation energy, the higher the diffusivity of water in the product. The activation energy found in this study was similar to those obtained by Doymaz (2006) Figure 8 shows that an increase of energy was required for the removal of product water, represented by integral values of isosteric heat of desorption (Q st ), as observed for several agricultural products (Jayendra et al 2005). Brooker et al (1992) and Khatchatourian (2012) stated that in order to remove water from grains with low water content a greater amount of energy is required on average than that required for wet products.…”

Section: Mathematical Modeling Of Drying Lemon Grasssupporting

confidence: 84%

Mathematical modeling of the drying kinetics of the leaves of lemon grass (Cymbopogon citratus Stapf) and its effects on quality

Coradi

Melo²,

Rocha³

2014

Idesia

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The aim of this study was evaluate the drying of the lemon grass plant (Cymbopogon citratus Stapf) at different air temperatures (40 °C, 50 °C, 60 °C and 70 °C) to adjust the experimental data obtained with different mathematical models and assess the quality of the plant after drying. A completely randomized design (CRD) was used with three drying replications for each speed and temperature of the drying air. The essential oil content extracted from the dried plant at 0.8 m s -1 and 1.3 m s -1 with manual control system was not affected by the drying process; the temperature of the drying air had a negative influence on the levels of the essential oil of the plant; drying with automatic control decreased the essential oil content for all velocities studied compared to the fresh plant; increments in the temperature of the drying air significantly reduced drying time. The mathematical model of Two Terms is adequate to describe the drying process of lemon grass plant (Cymbopogon citratus Stapf); diffusion values increased with increasing temperature of the drying air, while the value of activation energy was 62.84 kJ mol -1 .Key words: air, control, plant, velocity, temperature. RESUMEN El objetivo de este estudio fue evaluar el secado de la planta de hierba de limón (Cymbopogon citratus Stapf) a diferentes temperaturas de aire (40 °C, 50 °C, 60 °C y 70 °C) para ajustar los datos experimentales obtenidos con diferentes modelos matemáticos y evaluar la calidad de la planta después del secado. Un diseño completamente al azar (DCA) se utilizó con tres repeticiones para

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Section: Mathematical Modeling Of Drying Lemon Grasssupporting

confidence: 84%

Mathematical modeling of the drying kinetics of the leaves of lemon grass (Cymbopogon citratus Stapf) and its effects on quality

Coradi

Melo²,

Rocha³

2014

Idesia

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“…Observa-se que para conteúdos de umidades inferiores a 10% (b.s), o processo de dessorção requer uma elevação de energia substancial, caracterizado pelo acréscimo abrupto nos valores do calor isostérico. O mesmo efeito foi observado por Tolaba et al (2004) e por Jayendra Kumar et al (2005). Esse aumento reflete a força de interação da água com a monocamada do material.…”

Section: Resultsunclassified

Isotermas de dessorção de pimentão verde e energia envolvida no processo

Alves

Fóz

Nicoleti

2015

Braz. J. Food Technol.

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Isotermas de dessorção de pimentão verde e energia envolvida no processo Desorption isotherms of green bell peppers and the energy involved in the process*Autor Correspondente | Corresponding Author Recebido: Out. 01, 2014 Aprovado: Maio 18, 2015 ResumoEste trabalho teve como objetivos a obtenção das isotermas de dessorção do pimentão verde e a avaliação das propriedades termodinâmicas de sorção do fruto. As isotermas foram obtidas em função da temperatura (30°C, 40°C, 50°C e 60°C) em umidades relativas entre 4,0-90,0%. Os dados experimentais foram ajustados aos modelos matemáticos GAB, BET, Halsey, Henderson e Oswin para se descrever seu comportamento. Os resultados demonstram que o modelo de GAB descreveu com maior precisão as isotermas de dessorção do pimentão verde entre as faixas de atividade de água (a w ) selecionadas, em uma temperatura fixa. O calor isostérico de sorção (q st ) pôde ser determinado a partir de dados de sorção de umidade utilizando-se a derivada da equação de Clasius-Clapeyron, obtendo-se então o calor envolvido no processo de dessorção de umidade do pimentão verde fresco. A teoria da compensação entalpia-entropia ou isocinética foi aplicada aos dados experimentais, sugerindo que o processo de dessorção é conduzido pela entalpia. Palavras-chave: Calor isostérico; Secagem; Modelo de GAB; Compensação Entálpica-Entrópica. SummaryThis study aimed to obtain the desorption isotherms of green bell peppers and evaluate the thermodynamic properties of the moisture sorption of the fruit. The isotherms were obtained as a function of temperature (30°C, 40°C, 50°C and 60 °C) between 4.0 and 90.0% of relative humidity. The experimental data were fitted to the GAB, BET, Halsey, Henderson and Oswin mathematical models to describe their behaviour. The results showed that the GAB model described the sorption isotherms of green bell peppers with greater accuracy in the range of water activities (aw) selected, at a fixed temperature. The isosteric sorption heat (qst) could be determined from the moisture sorption data using the derivative of the Clasius-Clapeyron equation, to obtain the heat involved in the desorption process of the moisture of fresh green bell peppers. The enthalpy-entropy compensation or isokinetic theory was applied to the experimental data and suggested that the desorption process was driven by enthalpy.

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“…6, by reducing the water content in leaves, an increase in the energy necessary for the removal of water from the product was required, represented by integral values of the isosteric heat of desorption (Qst), as observed for several agricultural products. [21,34,35] To remove water from grains with low water content more energy is necessary on average than that required for wet products. [18,36,37] These results confirm that in products with higher water content, the force among water molecules and dry material decreases significantly.…”

Section: Mathematical Modeling and Drying Of Lemongrass Plantmentioning

confidence: 99%

Evaluation of Electrical Conductivity as a Quality Parameter of Lemongrass Leaves (Cymbopogon citratusStapf) Submitted to Drying Process

Coradi¹,

Melo²,

Rocha³

2014

Drying Technology

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This study aims to evaluate the quality of lemongrass plants after drying at different speeds (1.0, 1.5, 2.0 m s À1 ), temperatures (40, 50, 60, and 70 C), and drying air control systems (manual and automatic) using electrical conductivity as a parameter for evaluation. Firstly, we evaluated the time necessary for imbibitions of material in deionized water after drying for different air speeds and control systems. Secondly, the effect of temperature in fresh and dry plants was evaluated, comparing them with contents of essential oils and the quantity of ions leached by the electrical conductivity test. According to the results, the value of liquid diffusion increased with the increase of drying air temperature, and the value of activation energy was 62.84 kJ mol À1 . The quality of lemongrass plants evaluated by the electrical conductivity test was inversely proportional to the increase in drying air temperature, and the levels of essential oils were higher in dry plants with lower drying air temperatures. The adaptation of the electrical conductivity methodology to lemongrass plants was effective. A period of 33 h of imbibitions of the material in deionized water was necessary to obtain consistent results from leaching of potassium ions. The electrical conductivity can be used as a quality parameter for drying of medicinal plants.

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Effect of temperature on moisture desorption isotherms of kheer

Cited by 49 publications

References 28 publications

Mathematical modeling of the drying kinetics of the leaves of lemon grass (Cymbopogon citratus Stapf) and its effects on quality

Mathematical modeling of the drying kinetics of the leaves of lemon grass (Cymbopogon citratus Stapf) and its effects on quality

Isotermas de dessorção de pimentão verde e energia envolvida no processo

Evaluation of Electrical Conductivity as a Quality Parameter of Lemongrass Leaves (Cymbopogon citratusStapf) Submitted to Drying Process

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