Thermal Conductivity Measurements and Predictive Models for Frozen Guava and Passion Fruit Pulps

Pereira, Cláudio Márcio do Nascimento Abreu; Resende, Jaime Vilela de; Pereira, Gustavo G.; Giarola, Tales Márcio Oliveira; Prado, Mônica Elisabeth Torres

doi:10.1080/10942912.2011.566030

Cited by 7 publications

(6 citation statements)

References 17 publications

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“…Water is more available and has potential heat conduction activity. According to Pereira et al (2013), water is with the food component with the highest thermal conductivity and diffusivity. Thus, water contributes to the quicker temperature decrease that occurred on guava surfaces stored at 5°C.…”

Section: Surface Temperature Analysis By Ir Thermographymentioning

confidence: 99%

Using infrared thermography to evaluate the injuries of cold-stored guava

et al. 2015

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This study aimed to identify using the infrared (IR) thermography data the injuries of guavas during cooling and storage at different temperatures. Three experiments were performed at three different temperatures with one storage time. The first experiment was done with static air in a refrigerator at 5°C, the second experiment was conducted in a tunnel with forced air at 10°C, and the third experiment was conducted in an air conditioned environment at 20°C. Mechanical injuries caused by the impact of a pendulum were induced on guava surfaces. The surface temperatures were obtained for bruised and sound tissues during cooling and storage using an Infrared (IR) camera. With thermography, it was possible to distinguish the injured tissues of the fruits that were unaffected at temperatures of 5, 10 and 20°C in first hours of cooling. The results suggest that the storage of guava fruits at 5°C in static air resulted in cold-induced injury, while storage at 20°C resulted in an altered activity pattern. The stored guava fruits were analyzed for mass loss, firmness, color, total sugars, total pectin and solubility. The parameters values were lower during the forced-air cooling and storage at 5 and 10°C. When stored at 20°C, there was fruit maturation that caused tissue softening, which makes the fruits more susceptible to deterioration and thermographic readings showed opposite trends.

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Section: Surface Temperature Analysis By Ir Thermographymentioning

confidence: 99%

Using infrared thermography to evaluate the injuries of cold-stored guava

et al. 2015

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“…A continuous increase in mass was observed with decreasing temperature, with the largest increase observed for the range of 0 to -10°C. According to Pereira et al, [13] these two equations are presented as those featuring the lowest error in the prediction of the mass fraction of ice. Figure 3D shows the gain in percentage of ice fraction and conductivity for each variation of temperature drop to -5°C, starting is from 0 to -30°C, to better understand and evaluate the changes in thermal conductivity of mango pulp at low temperatures.…”

Section: Fraction Of Frozen Watermentioning

confidence: 99%

“…The experiment with the hot wire probe is based on the application of a constant heat flux from the heat source to the material, initially at equilibrium, thereby generating a variation in temperature of T o to T. [13,[15][16][17][18] To review the theoretical thermal conductivity, the existence of a relationship between the effective thermal conductivity of a food with the intrinsic conductivities of its components and their individual volume fraction is assumed, as described by Eq. (2).…”

Section: Mathematical Analysis and Theoretical Models For The Evaluatmentioning

confidence: 99%

“…The probe was calibrated for temperature and thermal conductivity. [13] First, the probe calibration was performed with respect to the temperatures of analysis (-30, -25, -20, -15, -10, -5, and 0°C). A thermometer was also [12] Composition per 100 g of edible portion [14] With the calibration, a correction factor f was obtained as shown in Eq.…”

Section: Sample Preparation For Analysis Of Thermal Conductivitymentioning

confidence: 99%

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Thermal Conductivity of Mango Pulp (Mangifera indicaL.) Cultivar “Ubari” in Freezing Temperatures

Giarola

Pereira

Resende

2015

International Journal of Food Properties

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The aim of this study was the experimental determination of the thermal conductivity of mango pulp of cultivar "ubari" and its subsequent comparison with values estimated using different structural models, such as the serial, parallel, and Maxwell-Eucken models. A linear heating probe calibrated with a solution of 10% sucrose was utilized. Heat was applied to the probe, generating an increase in temperature, which was recorded through a signal conditioning system. The thermal conductivity of the pulp was calculated from the slope obtained by linear regression of the natural logarithm of the temperature versus time. The data was within the range of 0.465 to 1.595 W/m.K for temperatures of 0 and -30°C, respectively, showing an increase of conductivity with freezing. The initial freezing temperature and ice fraction were determined at every temperature of analysis for further use in the models. The best fit to the experimental data were obtained using the Maxwell-Eucken model, yielding minimum and maximum errors of 10.8 and 17.8%, respectively. An exponential model was fitted, which allowed for the direct calculation of the thermal conductivity of mango pulp using only the knowledge of the recorded temperature during thermal processing.

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“…Knowledge of thermophysical properties then becomes essential for the optimization and design of the equipment used in processes involving heat transfer (MERCALI et al, 2011). A large amount of data has been published in the literature, but for tropical fruit pulps, data are still scarce (PEREIRA et al, 2013;RENO et al, 2011;AZOUBEL et al, 2005). At low temperatures, the measurements are quite difficult to perform due to the dependence of the properties on the continual change of the content of ice in the temperature range between 0 and -40 °C and the large variations in these properties (RENAUD et al, 1992).…”

Section: Introductionmentioning

confidence: 99%

Effect of concentration and temperature on the thermal conductivity of frozen acerola pulp

et al. 2015

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The purpose of this work was the experimental determination of the thermal conductivity of acerola pulp at concentrations of 5.5, 7.5, 9.5, 11.5 and 13.5 °Brix and temperatures of 0, -5, -10, -15, -20, -25 and -30 °C. The methodology used involved a hot wire probe, and the experimental results were compared with values estimated by several theoretical models (series, parallel and Maxwell-Eucken models) to evaluate the error involved. We observed an influence both of the concentration and the temperature on the thermal conductivity of the pulp. An increase of the conductivity with a decrease in temperature and in the solids concentration was detected. We observed the greatest increases in the range of 0 to -10 °C. Linear and polynomial equations were adjusted for the direct determination of the thermal conductivity of the pulp in the range of temperature and concentration studied. Key words: Frozen acerola pulp, thermal conductivity, hot wire probe, theoretical model ResumoA finalidade deste trabalho foi a determinação experimental da condutividade térmica da polpa de acerola nas concentrações de 5.5, 7.5, 9.5, 11.5 e 13.5 °Brix e nas temperaturas de 0, -5, -10, -15, -20, -25 e -30 °C. A metodologia utilizada foi a da sonda linear de aquecimento e os resultados experimentais obtidos foram comparados com valores estimados pelos modelos teóricos em série, paralelo e Maxwell-Eucken, avaliando o erro envolvido. Observou-se uma influência tanto da concentração quanto da temperatura na condutividade térmica da polpa. Houve aumento da condutividade com a redução da temperatura e da concentração de sólidos, observando-se os maiores aumentos na faixa de 0 a -10 °C. Equações polinomiais e lineares foram ajustadas para a determinação direta da condutividade térmica da polpa de acerola na faixa de temperatura e concentração estudada. Palavras-chave: Polpa congelada de acerola, condutividade térmica, sonda de fio quente, modelo teórico

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Thermal Conductivity Measurements and Predictive Models for Frozen Guava and Passion Fruit Pulps

Cited by 7 publications

References 17 publications

Using infrared thermography to evaluate the injuries of cold-stored guava

Using infrared thermography to evaluate the injuries of cold-stored guava

Thermal Conductivity of Mango Pulp (Mangifera indicaL.) Cultivar “Ubari” in Freezing Temperatures

Effect of concentration and temperature on the thermal conductivity of frozen acerola pulp

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