A novel infrared freeze drying (IRFD) technology to lower the energy consumption and keep the quality of Cordyceps militaris

Abstract

Please cite this article as: X.-f. Wu, M. Zhang and B. Bhandari, A novel infrared freeze drying (IRFD) technology to lower the energy consumption and keep the quality of Cordyceps militaris, Innovative Food Science and Emerging Technologies, https://doi. Abstract:A novel laboratory scale apparatus using infrared lamps replacing the electric heating plate for the freeze drying of Cordyceps militaris was developed in this study.The drying time, energy consumption, nutritional properties, antioxidant activities and main volatile compounds of Cordyceps militaris dried by infrared freeze drying (IRFD) and traditional freeze drying (TFD) at different drying temperatures (40, 50, 60 and 70 °C) were compared. Results indicated that drying at 40, 50 and 60 °C resulted in higher retention of cordycepin, total phenolics, hydroxyl radical scavenging activity, reducing power, 3-octanone, 3-octanol and 1,3-octadiene when compared with those dried at 70 °C. IRFD could reduce 7.21~17.78% of the drying time and 11.88~18.37% of the energy consumption at a constant drying temperature in comparison of TFD. In terms of quality, IRFD and TFD had similar retention effects on cordycepin, adenosine, hydroxyl radical scavenging activity and reducing power. Consequently, the results suggest that IRFD should be a promising approach for achieving high-quality dried products.Industrial relevance: IRFD could reduce 7.21~17.78% of the drying time and 11.88~18.37% of the energy consumption at a constant drying temperature in comparison of TFD without compromising the quality of the dried product. This study can help food processing industries to produce high quality freeze dried Cordyceps militaris and many other foods with an energy efficient freeze drying process.

Comparison of quality aspects and energy consumption of restructured taro and potato chips under three drying methods

“…To dry restructured (TR) and (PR) chips, hybrid infrared‐assisted freeze‐drying equipment (Changzhou One‐Step Drying Equipment Co., Ltd., Changzhou, Jiangsu, China) was used in this experiment as shown in Figure which has been used by Wu, Zhang, and Bhandari (). The pre‐frozen chips (200 g) were evenly placed on a wire mesh tray and kept on the shelf in the IRFD chamber.…”

The Freeze-Drying of Foods—The Characteristic of the Process Course and the Effect of Its Parameters on the Physical Properties of Food Materials

“…It was observed that an increase of the shelf temperature caused a shortening of the drying time by more than 50% [ 16 ]. The traditional freeze-drying of mushroom ( Cordyceps militaris ) also showed a significant reduction of the drying time of about 37% when the process temperature was increased from 40 to 70 °C [ 13 ]. The sublimation rate is generally higher at higher temperatures, but material dried at excessive temperatures can collapse and lose the pore structure created by the freezing process [ 87 ].…”

“…In order to control product stability, especially during the secondary drying stage, the temperature of the product should be limited to between 10 and 35 °C for heat-sensitive materials, and for less heat-sensitive materials, the temperature can be higher than 50 °C [ 54 , 90 ]. Higher temperatures of freeze-drying at the secondary stage accelerate the drying process because more energy is required to remove the remaining water in the material [ 13 , 91 ]. However, too high a temperature may cause the melting of ice during the sublimation step of drying, resulting in structural changes such as shrinkage [ 54 , 92 ].…”

“…However, too high a temperature may cause the melting of ice during the sublimation step of drying, resulting in structural changes such as shrinkage [ 54 , 92 ]. The selection of a proper shelf temperature should be based on the balance between the input and the required heat [ 13 ]. Additionally, the final quality of dried material is a crucial factor during the design of the freeze-drying process.…”

“…The effect of freeze-drying conditions on the nutritional properties, antioxidant activities [ 11 , 12 , 13 , 14 ], and glass transition characteristics [ 12 , 15 , 16 ] of different food materials can be found in the literature. It is widely believed that freeze-drying is the best method of drying.…”