News Update on Drying Methods : Nov 2020

Evaluation of energy consumption in different drying methods

This study was conducted to evaluate energy consumption in various drying systems including hot-air convection, use of microwave pretreatment with convection dryer, microwave drying, vacuum drying and infrared drying. Tests were conducted using pomegranate arils under various experimental conditions as follows. In convection dryer at six temperature levels (45, 50, 55, 60, 65 and 70 °C) and three air velocity levels (0.5, 1 and 1.5 m/s) at three pretreatments of control, 100 W microwave pretreatment for 20 min and 200 W microwave pretreatment for 10 min. Experiments in the microwave dryer were done at three power levels of 100, 200 and 300 W and in vacuum dryer at five temperature levels (50, 60, 70, 80, and 90 °C) under 250 kPa pressure. For infrared drying, there were four air velocity levels (0.3, 0.5, 0.7 and 1 m/s) and three illumination levels (0.22, 0.31 and 0.49 W/cm2). Experimental results showed that minimum and maximum energy consumption in pomegranate drying were associated with microwave and vacuum dryers, respectively. The use of microwave pretreatment in drying pomegranate arils in hot air dryer decreased drying time and energy consumption in comparison with pure convection drying. In infrared drying, it was found that drying time increased with air velocity which resulted in increased energy consumption. [1]

Chemical composition, physical properties, and antioxidant activities of yam flours as affected by different drying methods

Yams (the tubers of the Dioscorea spp.), consumed and regarded as medicinal food in traditional Chinese herbal medicine, are seasonal foods and easily deteriorate during storage. It is of great importance to prolong the storage of yams for supplying in the off-season and without losing nutritional functionality. Three varieties of yams, Dioscorea alata (cultivars of Tai-Nung no. 2 and Ta-Shan) and D. purpurea (cultivar of Ming-Chien), were made into flours by freeze-drying, hot air-drying, and drum-drying in this report. The proximate compositions and physical properties, as well as antioxidant activities, of yam flours were determined. While drying methods showed significant effects on the moisture contents of yam flours, they had no marked effects on other components of yam flours. Colour attributes and physical properties were all affected by drying methods to different extents. While freeze-drying usually preserved more antioxidant activity of the yam flours, yam flours made of different yam varieties showed different antioxidant mechanisms. [2]


Drying of Guava and Papaya: Impact of Different Drying Methods

Heat pump dryers (HPD) are known as high-energy-efficiency devices with low economic cost. As it is usually a closed system, the drying media can be substituted by inert gases. In this study, the effect of nitrogen and carbon dioxide on guava and papaya were investigated. Both drying kinetics and quality of these dried fruits resulting from the two methods were compared with normal air HPD, vacuum dryer, and freeze dryer. When using CO2, the effective diffusivity during the drying process was 44% higher in guava and 16.34% higher in papaya. There was less browning, faster rehydration, and more vitamin C retention in the final products. All these reveal the great potential of modified atmosphere heat pump dryer in the food drying industry. [3]

The Effect of Different Drying Methods on the Phytochemicals and Radical Scavenging Activity of Ceylon Cinnamon (Cinnamomum zeylanicum) Plant Parts

Aim: The research aimed at ascertaining whether the different drying methods and plant parts have effect on the radical scavenging activity and phytochemical properties of cinnamon as an herb/spice.

Methodology: Fresh samples of the cinnamon (Cinnamomum zeylanicum) was collected at the Aburi Botanical Gardens, Ghana. Some of the samples were sun, oven, room and freeze dried. The dried and fresh samples were extracted with methanol and water and the extract analyzed.

Results: Only the sun dried samples had the total phenolic and total flavonoid been degraded compared to the fresh sample. The flavonoid and phenolic contents and the DPPH radical scavenging activity were significantly expressed in different amounts in the root, stem, leaf and seed.

Conclusion: Generally, the drying influenced the phytochemical contents which are major contribution to the radical scavenging activity of the cinnamon. [4]

Effect of Drying Methods on the Chemical, Pasting and Functional Properties of Unripe Plantain (Musa paradisiaca) Flour

Aims: The effect of different drying methods on the chemical, pasting and functional properties of unripe plantain flour was evaluated in this study.

Study Design: Research study.

Place and Duration of Study: This study was carried out in the Food Chemistry and Food Processing Laboratories of the Department of Food Technology, Federal Polytechnic Ado-Ekiti, Ekiti State between October 2013 and April 2014.

Methodology: Equal quantity of unripe plantain pieces of the same dimension was subjected to four different drying methods: hot air oven (70°C), tray dryer (70°C, 1.5 m/s), fluidized bed dryer (70°C, 2.75 m/s) and sun drying until constant weight was obtained. The resulting samples were pulverized and then subjected to chemical, pasting and functional analysis.

Results: Hot air oven was the most effective in drying the unripe plantain to the lowest moisture content of 3.24%, the moisture content of unripe plantain dried with tray dryer was the highest (5.43%). The protein and ash contents of the unripe plantain dried with hot air oven; fluidized bed dryer; tray dryer and sun drying were 3.82% and 3.11%; 3.07% and 3.14%; 3.21% and 3.91%; 3.04% and 3.56% respectively. The pH and energy value of the four samples were in the range of 5.70 – 6.20 and 3.68 – 3.83 Kcal/g respectively. The peak and final viscosities of the unripe plantain dried with hot air oven; fluidized bed dryer; tray dryer and sun drying were 166.25 RVU and 293.33 RVU; 119.67 RVU and 126.50 RVU; 163.17 RVU and 243.58 RVU; 239.83 RVU and 124.33 RVU respectively. The water absorption capacity, oil absorption capacity and swelling power of samples dried with hot air oven; fluidized bed dryer; tray dryer and sun drying were 160 ml/100 g, 195 ml/100 g and 3.58; 160 ml/100 g, 200 ml/100 g and 3.65; 180 ml/100 g, 165 ml/100 g and 3.22; 130 ml/100 g, 210 ml/100 g and 3.05 respectively.

Conclusion: Oven and fluidized bed drying provided better alternatives to the traditional natural sun drying of unripe plantain especially in terms of final viscosity, peak viscosity, breakthrough viscosity; chemical and functional  properties. [5]

Reference

[1] Motevali, A., Minaei, S. and Khoshtagaza, M.H., 2011. Evaluation of energy consumption in different drying methods. Energy conversion and management, 52(2), pp.1192-1199.

[2] Hsu, C.L., Chen, W., Weng, Y.M. and Tseng, C.Y., 2003. Chemical composition, physical properties, and antioxidant activities of yam flours as affected by different drying methods. Food chemistry, 83(1), pp.85-92.

[3] Hawlader, M.N.A., Perera, C.O., Tian, M. and Yeo, K.L., 2006. Drying of guava and papaya: Impact of different drying methods. Drying Technology, 24(1), pp.77-87.

[4] Bernard, D., Isaac Kwabena, A., Daniel Osei, O., Achel Daniel, G., Achoribo Elom, S. and Sandra, A. (2014) “The Effect of Different Drying Methods on the Phytochemicals and Radical Scavenging Activity of Ceylon Cinnamon (Cinnamomum zeylanicum) Plant Parts”, European Journal of Medicinal Plants, 4(11), pp. 1324-1335. doi: 10.9734/EJMP/2014/11990.

[5] Arinola, S. O., Ogunbusola, E. M. and Adebayo, S. F. (2016) “Effect of Drying Methods on the Chemical, Pasting and Functional Properties of Unripe Plantain (Musa paradisiaca) Flour”, Current Journal of Applied Science and Technology, 14(3), pp. 1-7. doi: 10.9734/BJAST/2016/22936.

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