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Title: Overcoming issues associated with the scale-up of a continuous flow microwave system for aseptic processing of vegetable purees

Author
item KUMAR, PRABHAT - NC STATE UNIVERSITY
item CORONEL, PABLO - NC STATE UNIVERSITY
item TRUONG, VAN DEN
item SIMUNOVIC, JOSIP - NC STATE UNIVERSITY
item SWARTZEL, KEN - NC STATE UNIVERSITY
item SANDEEP, KANDIYAN - NC STATE UNIVERSITY
item CARTWRIGHT, GARY - NC STATE UNIVERSITY

Submitted to: Food Research International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2007
Publication Date: 6/18/2008
Citation: Kumar, P., Coronel, P., Truong, V., Simunovic, J., Swartzel, K.R., Sandeep, K.P., Cartwright, G.D. 2008. Overcoming issues associated with the scale-up of a continuous flow microwave system for aseptic processing of vegetable purees. Food Research International. 41(5):454-461.

Interpretive Summary: A microwave-assisted process for rapid sterilization and aseptic packaging of vegetable purees has been recently developed. However, non-uniform temperature distribution and control of processing parameters during continuous operations are the major hurdles in the implementation of continuous flow microwave heating at commercial scale. This study was undertaken to overcome issues associated with scale-up of the developed technology from pilot plant scale to industrial scale, and to conduct extended run times of 8 hours for processing green peas and carrot purees. The results indicated that installation of static mixers at the exit of the two microwave applicators of the system significantly improved the uniformity of the cross-sectional temperature profiles for both purees during the 8-hour test runs. Successful completion of processing the purees for 8 hours in 60-kW microwave system showed the potential for the scale-up of a continuous flow microwave system from pilot plant scale to industrial scale.

Technical Abstract: Continuous flow microwave heating is a promising alternative to conventional heating for aseptic processing of low-acid vegetable purees. However, non-uniform temperature distribution and control of processing parameters are the major hurdles in the implementation of continuous flow microwave heating. This study was undertaken to overcome issues associated with the scale-up of a continuous flow microwave system from pilot plant scale to industrial scale and to conduct extended run times of 8 hours based on the procedure developed. Dielectric properties and cross-sectional temperature profiles were measured during processing of green pea puree and carrot puree from 20 to 130°C in a 5-kW continuous flow microwave system. During processing of green peas, temperature differences of 8.6 and 5°C between the center and the wall of the applicator tube were observed at the outlet for center temperatures of 50 and 130°C, respectively. These differences were 32.9 and 3.6°C for carrot puree. For process scale-up, green pea puree and carrot puree were processed in a 60-kW microwave system with the objective of successful operation for at least 8 hours. Static mixers, installed at the exit of each of the microwave applicators, improved temperature uniformity for both purees. Successful completion of processing the purees for 8 hours in the 60-kW microwave system showed the potential for the scale-up of a continuous flow microwave system from pilot plant scale to industrial scale.