Prototype continuous microwave foam-mat dryer: design and fabrication
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ORIGINAL ARTICLE
Prototype continuous microwave foam-mat dryer: design and fabrication Ovais Shafiq Qadri1,2
•
Abhaya Kumar Srivastava1
Revised: 4 November 2020 / Accepted: 13 November 2020 Ó Association of Food Scientists & Technologists (India) 2020
Abstract A prototype microwave foam mat dryer with continuous operation was fabricated for tomato and guava. Results of preliminary studies on microwave foam mat drying of tomato and guava were used to design the prototype. The continuous foaming operation was achieved with the help of a submersible pump controlled by a time switch which ensured the delivery of pulp into foaming container and streamlined the delivery of foam on the drying surface (belt). The drying section presented a combination of hot air and microwaves, which resulted in accelerated heating and subsequently drying of the foam. Dried flakes were collected at the exit with the scrapper blade, which ensured appreciable recovery. The quality evaluation of guava pulp and tomato pulp dried at different microwave powers and inlet air temperatures revealed that the products dried at 1000 W microwave power and 50 °C exhibited excellent physicochemical properties in both the cases. Performance evaluation study depicted that the capacity of the dryer for guava drying was 4.84 l/h, the final moisture retention in the dried powder was 0.059 g H2O/g d.m, recovery was 98.34% and energy consumption was 1.32 kWh/l. Similarly, for tomato drying the capacity, final moisture content, recovery and energy consumption were 4.03 l/h, 0.062 g H2O/g d.m, 91.29% and 1.49 kWh/l respectively.
Abhaya Kumar Srivastava: Post humous (Deceased: December 2017). & Ovais Shafiq Qadri [email protected] 1
Department of Post Harvest Engineering and Technology, Aligarh Muslim University, Aligarh, India
2
Department of Biotechnology, Thapar Institute of Engineering and Technology, Patiala, India
Keywords Foam mat drying Microwave dryer Guava drying Prototype dryer
Introduction Drying of foods is one of the oldest methods of food preservation. Water is the main constituent of most of the foods and an important requirement for the spoilage of foods by internal or external factors. The affinity of different food constituents to water is different, and depending on composition, the foods show variation in drying characteristics. Removal of moisture from foods invariably increases their keeping quality in addition to reduction in bulk, and easy handling, transportation and storage (Singh and Heldman 2009). With advancement in technology, the methods of drying have also evolved, for instance, freeze drying, microwave drying, foam mat drying, spray drying and many more (Sagar and Suresh 2010). Most of these drying methods are in practice, as each method possesses features for a specific type of drying, making the comparison between the drying processes difficult. Liquid and pulpy foods can be dried by many methods and foam mat drying is one such method. Foam-mat drying of aqueous foods presents a promising future in the drying
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