Studies on microwave assisted hot air drying characteristics and rehydration of Bitter gourd (Momordica charantia L.)

Drying characteristics of persimmon, cv. “Rojo Brillante”, slabs were experimentally determined in a hot air convective drier at drying temperatures of 45, 50, 55, 60, and 65 °C at a fixed air velocity of 2.3 m/s. It was observed that the drying temperature affected the drying time, shrinkage, and colour. Four empirical mathematical models namely, Enderson and Pabis, Page, Logarithmic, and Two term, were evaluated in order to deeply understand the drying process (moisture ratio). The Page model described the best representation of the experimental drying data at all investigated temperatures (45, 50, 55, 60, 65 °C). According to the evaluation of the shrinkage models, the Quadratic model provided the best representation of the volumetric shrinkage of persimmons as a function of moisture content. Overall, higher drying temperature (65 °C) improved the colour retention of dried persimmon slabs.

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Hot air drying combined vacuum-filling nitrogen drying of apple slices: Drying characteristics and nutrients

Proceedings of 21th International Drying Symposium ◽

10.4995/ids2018.2018.7477 ◽

2018 ◽

Author(s):

Xiaoli Huang ◽

T. Li ◽

S.N. Li ◽

Z.H. Wu ◽

J. Xue

Keyword(s):

Moisture Content ◽

Drying Rate ◽

Slice Thickness ◽

Relative Pressure ◽

Hot Air Drying ◽

Air Drying ◽

Drying Characteristics ◽

Hot Air ◽

Apple Slices ◽

Apple Slice

In this paper, hot air drying (HAD) was applied when moisture content of apple slices range from 50% to 86%, and then vacuum-filling nitrogen drying (VFND) was used till moisture content reaching 7%. Results showed that, the drying rate of apple slice during VFND period increased with temperature increment and decreased with increment of slice thickness; compared to freezing dried samples, samples dried in this research were owned lower Vc and higher flavonoid; when HAD (70℃,3.0m/s)+VFND(relative pressure 0.08MPa, 50℃) and thickness of 6.0mm, nutrients reached better levels: retentions of Vc, total phenolics and flavonoid were 1.63mg/100g, 4.07mg/100g and 2.10mg/100g, respectively. Keywords: apple slices, hot air drying, vacuum-filling nitrogen drying, drying rate, nutrients

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Heat Transfer Characteristics and Kinetics of Camellia oleifera Seeds During Hot-Air Drying

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4045118 ◽

2019 ◽

Vol 12 (3) ◽

Cited By ~ 2

Author(s):

Dan Huang ◽

Yuchao Tao ◽

Wei Li ◽

S. A. Sherif ◽

Xiaohong Tang

Keyword(s):

Heat Transfer ◽

Camellia Oleifera ◽

Heat Transfer Characteristics ◽

Hot Air Drying ◽

Drying Time ◽

Air Drying ◽

Drying Characteristics ◽

Hot Air ◽

Rate Period ◽

Kinetics Of

Abstract The heat transfer characteristics and kinetics of Camellia oleifera seeds under hot-air drying were investigated at different temperatures (40, 60, and 80 °C) and loading densities (0.92, 1.22, and 1.52 g/cm2) with a constant air velocity of 1 m/s. Twelve common drying kinetic models were selected to fit the experimental data. The most suitable model was chosen to describe the hot-air drying process of C. oleifera seeds and help in its optimization. The results showed that the drying temperature has a significant influence on the hot-air drying characteristics of C. oleifera seeds. As the drying air temperature increases, the drying time decreases. The effect of the loading density on the drying characteristics of C. oleifera seeds is much smaller than that of temperature. With the increase in the loading density, the drying time slightly increases. The hot-air drying curve of C. oleifera seeds consists of a very short acceleration rate period at the beginning and a long falling rate period, indicating that the drying of C. oleifera seeds is mainly controlled by the diffusion of moisture inside the material. An effective moisture diffusion coefficient of C. oleifera seeds was estimated to range from 0.81256 × 10−9 to 3.28496 × 10−9 m2/s within the temperature range studied. The average activation energy was 28.27979 kJ/mol. The logarithmic model was found to be the best model to describe the kinetics of hot-air drying of C. oleifera seeds.

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Microwave and Blanching Pretreatments for Hot Air Drying of Orange-Fleshed Sweet Potato Slices (Ipomoea batatas)

International Journal of Food Science ◽

10.1155/2020/8872429 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12

Author(s):

Ernest Abano

Keyword(s):

Sweet Potato ◽

Ipomoea Batatas ◽

Moisture Diffusivity ◽

Hot Air Drying ◽

Air Drying ◽

Logarithmic Model ◽

Microwave Assisted ◽

Hot Air ◽

Orange Fleshed Sweet Potato ◽

Potato Slices

Microwave and steam blanching as pretreatments to hot air drying of orange-fleshed sweet potato (OFSP) were studied. The air-drying experiment was performed at constant temperature of 70°C and airflow of 1.0 m/s. The effective moisture diffusivity varied from 1.5 × 10 − 9 to 4.4 × 10 − 9 m2/s, and 1.1 × 10 − 10 to 7.9 × 10 − 10 m2/s, for the microwave and blanched assisted hot air drying, respectively. The activation energy obtained for the various microwave-assisted hot air drying was 29.1 W/mm for 4 min, 68.1 W/mm for 3 min, and 79.7 W/mm for 2 min. Ascorbic acid degradation and formation of brown pigments in the OFSP slices were lower in microwave than in steam blanch-assisted drying. Microwave-assisted drying of OFSP is best governed by Page model, M R = exp − k t n , while the blanch-assisted followed the logarithmic model, M R = a exp − k t + c . To produce better quality OFSP flour, it is recommended to cut the tubers into 3 mm slices, microwave at a power of 630 W for 2 min or blanch for 1 min, 43 seconds prior to hot air drying.

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