Drying constant: literature data compilation for foodstuffs

Krokida, Magdalini; Foundoukidis, E; Maroulis, Z.B.

doi:10.1016/s0260-8774(03)00136-5

Cited by 32 publications

(28 citation statements)

References 44 publications

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“…As collapse and shrinkage are related phenomena, there must be a relationship between the average diffusion coefficient in each zone and its average thickness or, rather, with its average moisture content (Gekas and Lamberg 1991). In general, the diffusion coefficient tends to increase for higher temperatures and higher moisture contents (Krokida et al 2004). The diffusion coefficients obtained in this study for the apple pectic gels (Fig.…”

Section: Low-moisture Zonementioning

confidence: 63%

“…The main components of such models are the drying kinetic expressions describing the average product moisture content and temperature as a function of time. In some contributions, empirical models are developed to predict only the variation of moisture content (Krokida et al 2004); these models are useful for quick-drying time estimations but do not identify the drying mechanism and cannot be used to estimate quality losses. In contrast, some models have been developed for cellular foods, which are important to provide basic knowledge for drying science (Crapiste et al 1988a, b).…”

Section: Introductionmentioning

confidence: 99%

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Apple Pectic Gel Produced by Dehydration

Diaz

Giannuzzi

Giner

2007

Food Bioprocess Technol

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A novel, flexible sheet-like food formed by the high methoxyl pectin-sugar-acid gelation during drying of apple puree was investigated to characterize drying-related properties. Product volume was reduced by 68% over the process, and this shrinkage was successfully modeled by assuming the volume reduction equal to the volume of water evaporated. The sorption isotherm at 25°C was determined, and a new expression for the moisture content, W, as a function of water activity, a w , of the type W ¼ C 1 exp C 2 a C3 w À Á resulted as the most accurate for this J-shaped isotherm. The drying kinetics was studied at 50, 60, and 80°C in a tray dryer. No constant drying rate period was found, and the drying curve was divided in high-and low-moisture zones. For high moistures, an internal-external mixed control diffusive model coupling mass and heat transfer was applied to obtain a mass transfer Biot number of 2.1. In the low-moisture zone, a diffusive, isothermal drying model for strict internal control was utilized. Diffusivities varied around 1×10-9 m 2 /s for high moistures and were about ten times lower at low moistures, although the activation energies were comparable (15,259 and 16,800 J/mol, respectively). The drying time at 60°C was 6.67 h. The product scored four points out of five in a sensory evaluation of general acceptability. Keywords Fruit leather . Hot-air drying . Non-isothermal drying Nomenclature A mass transfer area for evaporation (m 2 ) a w water activity, decimal A h and B h fitting parameters of the Halsey model A o and B o fitting parameters of the Oswin model a, b, c, and d coefficients of the third degree polynomials W=f(t) Bi mass transfer Biot number C p specific heat of apples (J kg −1 K −1 ) C constant of the GAB model C 1 , C 2 , C 3 parameters of the new sorption model D effective diffusion coefficient of water (m 2 /s) d average laminate thickness (m) D 0 Arrhenius preexponential factor (m 2 /s) E a activation energy (J/mol) f multiplier of the preliminary Arrhenius preexponential factor h heat transfer coefficient (W/°C m 2 ) h a air absolute humidity (kg vapor/kg dry air) h r air relative humidity (decimal) k constant of the GAB model L wd product heat of desorption (J/kg) Food Bioprocess Technol (L w heat of vaporization of water (J/kg) m product mass at any time (kg) m 0 initial product mass (kg) m d product dry matter (kg) m wev mass of water evaporated (kg) MSS sum of squares of the deviation M 1n , M 2n , M 3n and M 4n values of parameters of Eq. 15 r 2 coefficient of determination R universal gas constant 8.314 J mol −1 K −1 t time (s) T a air temperature (°C) T 0 product temperature at t=0 (°C) T product temperature (°C) V product volume at W (m 3 ) V 0 initial product volume (m 3 ) V d dry matter volume (m 3 ) V wev volume of water evaporated (m 3 ) W moisture content (dec., d.b.) W product average moisture content (dec., d.b.) W e equilibrium moisture content (dec., d.b.) W 0 initial moisture content (dec., d.b.) W m monolayer moisture content of the GAB model (dec., d.b.) W ad d...

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Section: Low-moisture Zonementioning

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Apple Pectic Gel Produced by Dehydration

Diaz

Giannuzzi

Giner

2007

Food Bioprocess Technol

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“…Observa-se, na Figura 3, que, com o aumento da temperatura do ar de secagem, ocorre maior taxa de remoção de água do produto, como observado por diversos pesquisadores para inúmeros produtos agrícolas (OZDEMIR & DERVES, 1999;BASUNIA & ABE, 2001;YALDIZ, et al, 2001;AZZOUZ et al, 2002;KAYMAK-ERTEKIN, 2002;AKPINAR et al, 2003;LAHSASNI et al, 2004;ERTEKIN & YALDIZ, 2004;MOHAPATRA & RAO, 2005). O tempo necessário para que o feijão atingisse o teor de água de 12% b.u.…”

Section: Resultsunclassified

“…Recentemente, têm sido realizados inúmeros trabalhos com o objetivo de identificar as características de diversos produtos agrícolas durante a secagem, como: trigo (SUN & WOODS, 1994), feijão-preto (AFONSO JÚNIOR & CORRÊA, 1999, arroz em casca (BASUNIA & ABE, 2001), uva (YALDIZ et al, 2001RAMOS et al, 2004;RAMOS et al, 2005), pimenta (KAYMAK-ERTEKIN, 2002;AKPINAR et al, 2003), pêra (LAHSASNI et al, 2004) e trigo parbolizado (MOHAPATRA & RAO, 2005), dentre outros. Durante a modelagem e a simulação dos processos de secagem de produtos agrícolas, diversos trabalhos correlacionaram satisfatoriamente os coeficientes dos modelos ajustados aos parâmetros de secagem, principalmente a temperatura, a umidade relativa e a vazão do ar (MADAMBA et al, 1996;AFONSO JÚNIOR & CORRÊA, 1999;OZDEMIR & DERVES, 1999;AZZOUZ et al, 2002;KROKIDA et al, 2003;KROKIDA et al, 2004;MOHAPATRA & RAO, 2005).…”

Section: Introductionunclassified

“…Durante a modelagem e a simulação dos processos de secagem de produtos agrícolas, diversos trabalhos correlacionaram satisfatoriamente os coeficientes dos modelos ajustados aos parâmetros de secagem, principalmente a temperatura, a umidade relativa e a vazão do ar (MADAMBA et al, 1996;AFONSO JÚNIOR & CORRÊA, 1999;OZDEMIR & DERVES, 1999;AZZOUZ et al, 2002;KROKIDA et al, 2003;KROKIDA et al, 2004;MOHAPATRA & RAO, 2005).…”

Section: Introductionunclassified

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Modelagem matemática para a descrição do processo de secagem do feijão (Phaseolus vulgaris L.) em camadas delgadas

Corrêa¹,

Resende

Martinazzo³

et al. 2007

Eng. Agríc.

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RESUMO:O objetivo do presente trabalho foi a obtenção e a avaliação das curvas de secagem do feijão (Phaseolus vulgaris L.) e ajustar diferentes modelos matemáticos aos valores experimentais do teor de água para diversas condições do ar. Foram utilizados grãos de feijão colhidos com teor de água de 0,92 (b.s.) e submetidos à secagem até o teor 0,14 (b.s.) sob condições controladas de temperatura (35; 45 e 55 °C) e umidade relativa do ar de secagem de 40 ±2%. Aos dados experimentais, foram ajustados 12 modelos matemáticos citados na literatura específica e utilizados para a representação do processo de secagem de produtos agrícolas. Pelos resultados obtidos e baseando-se em parâmetros estatísticos, pode-se concluir que metade dos modelos testados representa bem o fenômeno de secagem do feijão. Dentre esses, o modelo clássico de Page foi selecionado, pela sua simplicidade e pelo seu uso disseminado no meio científico, para descrever a cinética de secagem dos produtos vegetais. A relação entre a constante de secagem k desse modelo e a temperatura do ar pode ser descrita pela relação de Arrhenius, apresentando energia de ativação de 10,08 kJ mol -1 . PALAVRAS-CHAVE:feijão, modelagem matemática, teor de água. MATHEMATICAL MODELLING FOR DESCRIBING THE DRYING PROCESS OF THE EDIBLE BEAN (Phaseolus vulgaris L.) IN THIN LAYERS ABSTRACT:The objective of this work was to obtain and to evaluate the drying curves of edible bean (Phaseolus vulgaris L.) and to fit different mathematical models to different experimental data of moisture content and drying air conditions. Edible beans harvested at moisture content of 0.92 (d.b.) were dried until achieving the moisture content of 0.14 (d.b.) under controlled drying air temperatures (35; 45 and 55 °C) and relative humidity of 40 ±2%. Twelve mathematical models cited in the literature were fitted to the experimental data in order to represent the drying process. According to the results and based on the statistical parameters it can be concluded that half of the tested models represent well the edible bean drying phenomena. Within them the classic Page model was selected due to its simplicity and widely use within researchers to describe the agricultural product drying kinetic. The relationship between the drying constant k and the drying air temperature can be described through Arrhenius's equation presenting activation energy of 10.08 kJ mol -1 .

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Modelling of air drying of Hacıhaliloglu‐type apricots

Mengeş

Ertekin

2005

J Sci Food Agric

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In this study a laboratory dryer was used for the thin layer drying of sulfured and nonsulfured apricots. The moisture ratio values throughout the drying process were calculated by 14 different mathematical models, namely Newton, Page, modified Page, modified Page-II, Henderson and Pabis, logarithmic, two-term, two-term exponential, Wang and Singh, Thompson, diffusion approximation, modified Henderson and Papis, Verma et al. and Midilli et al. models. Root mean square error, reduced chi-square, mean bias error, adjusted R-square and modelling efficiency were used as statistical parameters to determine the most suitable model among them. According to the results, the Page model was chosen to explain the thin layer drying behaviour of sulfured and non-sulfured apricots. The effects of drying air temperature (T ) and velocity (V ) on the constants and coefficients of the best moisture ratio model were determined by multiple regression analysis. The moisture ratio (MR) could be predicted by the Page model equation MR = exp(−kt n ) with constants and coefficients k = 0.470893 + 0.078775V and n = 0.017786exp(0.051935T ) for sulfured apricots and k = 4.578252 + 1.144643T and n = 0.888040 + 0.145559V for non-sulfured apricots. It is possible to predict the moisture content of the product with the generalised Page model incorporating the effects of drying air temperature and velocity on the model constants and coefficients in the ranges T = 70-80 • C and V = 1-3 m s −1 . This developed model showed acceptable agreement with the experimental results, explained the drying behaviour of the product and could also be used for engineering applications.

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Drying constant: literature data compilation for foodstuffs

Cited by 32 publications

References 44 publications

Apple Pectic Gel Produced by Dehydration

Apple Pectic Gel Produced by Dehydration

Modelagem matemática para a descrição do processo de secagem do feijão (Phaseolus vulgaris L.) em camadas delgadas

Modelling of air drying of Hacıhaliloglu‐type apricots

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