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Research Project: New Sustainable Processing Technologies to Produce Healthy, Value-Added Foods from Specialty Crops

Location: Healthy Processed Foods Research

Title: A pilot scale electrical infrared dry-peeling system for tomatoes: design and performance evaluation

item Pan, Zhongli
item LI, XUAN - University Of California
item KHIR, RAGAB - University Of California
item EL-MASHAD, HAMED - University Of California
item ATUNGULU, GRIFFITHS - University Of Arkansas
item McHugh, Tara
item DELWICHE, MICHAEL - University Of California

Submitted to: Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2015
Publication Date: 9/15/2015
Citation: Pan, Z., Li, X., Khir, R., El-Mashad, H.M., Atungulu, G., McHugh, T.H., Delwiche, M. 2015. A pilot scale electrical infrared dry-peeling system for tomatoes: design and performance evaluation. Biosystems Engineering. 137:1-8.

Interpretive Summary: The study demonstrated the feasibility of using IR heating as a sustainable approach for tomato peeling process in a pilot scale. A vacuum treatment is needed after the IR heating to provide the required pressure differences across the tomato skin, which assures the cracking of tomatoes before the pinch roller system. An adequate pinch roller system should be installed after the vacuum unit to assure the removal of cracked skins. For all IR treatment times, the peeled tomatoes were firm and had appealing surface integrity. However, the peeling yields and texture of peeled tomato slightly decreased with the increase of IR heating time.

Technical Abstract: A pilot scale infrared dry-peeling system for tomatoes was designed and constructed. The system consisted of three major sections including the IR heating, vacuum, and pinch roller sections. The peeling performance of the system was examined under different operational conditions using tomatoes with different cultivars and sizes. Three lines of tomatoes were heated and processed at the same time at a residence time of 125 seconds and achieved a percentage of fully peeled tomatoes of 85%, a peeling yield of 82%, and an average thickness of peeled tomato skin of 0.75 mm. When tomatoes were loaded as a single line, the required heating time was reduced to a range from 80 to 100 s, depending of tomato size, for achieving the same level of peeling percentage and yield. The presence of the vacuum section could achieve cracks in 100% of the tomatoes after IR heating. The peeled products from IR heating had high firmness and appealing surface integrity, which indicated desirable quality characteristics. Because the dry-peeling is a chemical- and water-free process, residuals of tomato skins after IR peeling could be easily utilized as value-added byproducts.