Drying Kinetic Studies on Single Layer Thompson Seedless Grapes Under Controlled Heated Air Conditions

The aim of this research was to study the behaviour of the drying kinetics of pepino fruit (Solanum muricatum Ait.) at five temperatures (50, 60, 70, 80 and 90°C). In addition, desorption isotherms were determined at 20, 40 and 60°C over a water activity range from 0.10 to 0.90. The Guggenheim, Anderson and de Boer model was suitable to depict the desorption data. A monolayer moisture content from 0.10 to 0.14 g water g −1 d.m. was reported. The equations of Newton, Henderson-Pabis, Modified Page, Wang-Singh, Modified Henderson-Pabis, Logarithmic as well as standardised Weibull were tested for modelling drying kinetics. Besides, Fick's second law model was used to calculate the water diffusion coefficient which increased with temperature from 2.55 to 7.29× 10 −10 m 2 s −1 , with estimated activation energy of 27.11 kJ mol −1 . The goodness of fit of the models was evaluated using sum squared error and chi-square statistical tests. The comparison of the experimental moisture values with respect to the calculated values showed that the standardised Weibull model presented the best goodness of fit, showing that this equation is very accurate for simulating drying kinetics for further optimisation of drying times. Nomenclature a w Water activity (dimensionless) X we Equilibrium moisture content (g water g −1 d.m.) X wt Moisture content (g water g −1 d.m.) X wo Initial moisture content (g water g −1 d.m.) X m Monolayer moisture content (g water g −1 d.m.) C, K Parameters of GAB model D we Water diffusion coefficient (m 2 s −1 ) L Half-thickness of the slab (m) k i Kinetic parameters (min −1 ) n i , c Empirical parameters (dimensionless) α Shape parameter (dimensionless) of the Weibull model β Scale parameter (min) of the Weibull model t Drying time (s, min) i Number of terms R Universal gas constant (8.314 J mol −1 K −1 ) T Absolute temperature (K) E a Activation energy (kJ mol −1 )

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“…14). It may be pointed out that the lower the value of SSE and chi-square, the better will be the goodness of fit (Pangavhane et al 2000).…”

Section: Statistical Evaluation Of the Modelsmentioning

confidence: 99%

Characteristics of Convective Drying of Pepino Fruit (Solanum muricatum Ait.): Application of Weibull Distribution

Uribe

Vega‐Gálvez

Scala

et al. 2009

Food Bioprocess Technol

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“…Although many literatures covering mathematical modeling of drying of food and agricultural products by using empirical, semi‐empirical and theoretical models have been reported by several researchers (Bakari and Hobani 2000; Pangavhane et al. 2000; Akpinar et al.…”

Section: Introductionmentioning

confidence: 99%

Drying and Rehydration Characteristics of Sour Cherry (Prunus Cerasus L.)

Aghbashlo¹,

Kianmehr

Hassan-Beygi

2009

Journal of Food Processing and Preservation

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The effect of air temperature and velocity on the drying kinetics of sour cherry was investigated using a laboratory scale static‐type dryer at air temperatures of 60, 70 and 80C and air velocities of 0.3, 0.6 and 0.9 m/s. The Weibull distribution model was fitted to experimental data using nonlinear regression analysis techniques in the MATLAB computer program. The high regression coefficients (R2 > 0.998) and low reduced chi‐square and root mean square error indicated that the Weibull model is suitable for predicting moisture ratio. Correlations of the Weibull model constants with the variables T and V were determined. The effective diffusivity of sour cherry varied between 3.46 × 10‐9 and 13.08 × 10‐9 m2/s. The activation energy of sour cherry was in the range of 64.39–66.05 kJ/mol. Rehydration tests indicated that the rehydration capacity of dried samples at air temperature of 70C and air velocity of 0.3 m/s is better than other experiments. PRACTICAL APPLICATIONS All commercial flow dryers are designed based on thin‐layer drying principles. One of the most important aspects of drying technology is the modeling of the drying process. The prediction of drying kinetics of agricultural products under various conditions is very useful in design and optimization of dryers. In this paper, the Weibull distribution model is used for modeling thin‐layer drying of sour cherry. Weibull's model constants include the effect of drying variable on drying kinetics and could be a useful tool for the modeling of drying kinetics. The rehydration characteristics of a dried product are used as a quality index and they indicate the physical and chemical changes during drying as influenced by processing conditions, sample pretreatment and composition. Optimizing the drying conditions in order to obtain the dried product with good rehydration characteristics is vital, since rehydration governs the subsequent operations.

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“…The drying of the grapes was considered to have taken place in the falling rate period only, which would be indicative of a diffusion-controlled drying mechanism. Pangavhane [21] showed the drying rate to be more strongly influenced by air temperature than either the velocity or humidity of the drying air. Ethyl oleate can increase drying rates both in the early stages, by the formation of micropores on the surface of the skin, and in the later stages, by improving the internal water diffusion [22].…”

Section: Resultsmentioning

confidence: 99%

Modeling of the Seedless Grape Drying Process using the Generalized Differential Quadrature Method

et al. 2007

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Mathematical modeling of the grape drying process is important in understanding the transport phenomena involved in the production and processing of dried grapes. Drying models proposed in the literature have simplifying assumptions, and thus ignore important phenomena such as shrinkage and changes in transport properties which occur during the drying process. Consequently, a mathematical model is developed for the seedless grape drying process, which considers the effects neglected in previous models. Since an analytic solution to this nonlinear model is impossible, the generalized differential quadrature method is used to solve the models' equations. The model is validated with experimental data obtained from a laboratory scale convective tray dryer operating at 50-70°C and an air velocity of 1.5 m/s. Model predictions are in close agreement with experimental data due to the inclusion in the model of shrinkage and variation in moisture diffusivity. Model results can serve as a framework to improve the performance of existing and novel dryers, and also in the design of process simulators for dryers.

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Drying Kinetic Studies on Single Layer Thompson Seedless Grapes Under Controlled Heated Air Conditions

Cited by 22 publications

References 12 publications

Characteristics of Convective Drying of Pepino Fruit (Solanum muricatum Ait.): Application of Weibull Distribution

Characteristics of Convective Drying of Pepino Fruit (Solanum muricatum Ait.): Application of Weibull Distribution

Drying and Rehydration Characteristics of Sour Cherry (Prunus Cerasus L.)

Modeling of the Seedless Grape Drying Process using the Generalized Differential Quadrature Method

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