Temperature gradient control during microwave combined with hot air drying. (May 2018)

• Record Type: Journal Article
• Authors: Xu, Wanxiu; Song, Chunfang; Li, Zhenfeng; Song, Feihu; Hu, Shaogang; Li, Jing; Zhu, Guanyu; Vijaya Raghavan, G.S.
• Is Part Of: Biosystems engineering. Volume 169(2018)
• Page Start: 175
• Page End: 187
• Publication Date: 2018-05
• Subjects: Carrot -- Temperature difference -- Drying rate -- Quality; Bioengineering -- Periodicals; Agricultural engineering -- Periodicals; Biological systems -- Periodicals; Génie rural -- Périodiques; Systèmes biologiques -- Périodiques; 631
• DOI: 10.1016/j.biosystemseng.2018.02.013
• Languages: English
• ISSNs: 1537-5110

Abstract

Abstract : Fresh carrot cubes were blanched and dried by microwave processing combined with hot air drying. Material temperature, temperature difference and size of cube were optimised in terms of total vitamin C content, colour change, drying time, sensory evaluation and rehydration ratio of dried samples. During a stage under the optimal drying condition, drying rate was affected by temperature gradient, as evidenced by changed shrinkage. The effect of different temperature gradients on the drying rate and quality was compared with that under the optimal condition by using fitted shrinkage models of the optimised material temperature, temperature difference and size of cube. The quality of dried carrot cubes under the average temperature gradient (ATG) of 6 °C mm −1 was better than that under other ATGs. A simple linear control method was developed based on the control for industrial production. Results showed that the product quality and drying time of samples in linear control were similar to those dried at 6 °C mm −1 . Highlights: To design and build a microwave combined with hot air dryer and test the system. To determine the optimum drying condition through RSM. To establish a shrinkage mathematical model based on the optimal condition. To study the effect of average temperature gradient on the drying kinetics. To develop a simplified temperature control method without mass measurement.