scholarly journals Hot air drying of coconut residue: shelf life, drying characteristics, and product quality

Author(s):  
J S Jongyingcharoen ◽  
P Wuttigarn ◽  
R Assawarachan
Foods ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 101 ◽  
Author(s):  
Senadeera ◽  
Adiletta ◽  
Önal ◽  
Di Matteo ◽  
Russo

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.


Author(s):  
Xiaoli Huang ◽  
T. Li ◽  
S.N. Li ◽  
Z.H. Wu ◽  
J. Xue

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


Author(s):  
Dan Huang ◽  
Yuchao Tao ◽  
Wei Li ◽  
S. A. Sherif ◽  
Xiaohong Tang

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.


Author(s):  
Takahiro Orikasa ◽  
Long Wu ◽  
Yasumasa Ando ◽  
Yoshiki Muramatsu ◽  
Poritosh Roy ◽  
...  

Changes in the quality of sweet potato during hot air drying, such as L-ascorbic acid, sugar content, surface color and hardness, and drying characteristics, were investigated at temperatures of 30, 40, 50, and 60°C. Equilibrium moisture contents (EMC) of sweet potato samples in the desorption process were measured by a static method at the four aforementioned temperatures and six selected relative humidity levels. Using both the measured moisture content data in the drying test and the EMC values, hot air drying characteristics of sweet potato was estimated. Changes in L-ascorbic acid content of sweet potato during hot air drying was measured, wherein a first-order reaction rate equation was applied to model the change in decomposition of L-ascorbic acid content. In addition, surface color, sugar content, and surface hardness were also measured. The total color change (?E) of the samples was observed to decrease as drying temperature was increased. The effects of sample sugar concentration on surface hardening during hot air drying of sweet potato are discussed.


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