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Title: Continuous flow microwave-assisted processing and aseptic packaging of purple-fleshed sweetpotato purees

Author
item STEED, LAURIE - NC STATE UNIVERISTY
item Truong, Van Den
item SIMUNOVIC, JOSIP - NC STATE UNIVERSITY
item SANDEEP, KANDIYAN - NC STATE UNIVERSITY
item KUMAR, PRABHAT - NC STATE UNIVERSITY
item CARTWRIGHT, GARY - NC STATE UNIVERSITY
item SWARTZEL, KEN - NC STATE UNIVERSITY

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/2008
Publication Date: 11/7/2008
Citation: Steed, L.E., Truong, V., Simunovic, J., Sandeep, K.P., Kumar, P., Cartwright, G.D., Swartzel, K.R. 2008. Continuous flow microwave-assisted processing and aseptic packaging of purple-fleshed sweetpotato purees. Journal of Food Science. 73(9):E455-E462.

Interpretive Summary: This study aimed to evaluate the application of microwave-assisted technology in aseptic processing of purple-fleshed sweetpotato puree (PFSP). Pumpable purees from purple-flesh sweetpotatoes (PFSP) were subjected to microwave heating using a 915 MHz continuous flow system, followed by aseptic packaging in flexible containers to obtain a shelf-stable product. Results demonstrated uniformity in heating of the puree were achieved at sterilization temperatures (>121 ºC). Pilot-scale test runs produced PFSP packages that were shelf-stable for over 12 months at room temperature. Total phenolic content of PFSP slightly increased (5.9%) and anthocyanin content decreased by 14.5% with microwave heating. However, antioxidant activity of the purees did not significantly change as a result of microwave processing. Color values showed that microwave processed samples differed from fresh puree in saturation and hue angle, but not in overall color change. Overall, high quality retention can be obtained by microwave processing and aseptic packaging of PFSP purees that can be used as functional food ingredients in processed foods.

Technical Abstract: Pumpable purees from purple-flesh sweetpotatoes (PFSP) were subjected to microwave heating using a 915 MHz continuous flow system, followed by aseptic packaging in flexible containers to obtain a shelf-stable product. Initial test runs were conducted using a 5 kW microwave unit to measure dielectric in-line properties and examine the puree temperature profiles. Results demonstrated uniformity in heating of the puree at sterilization temperatures (>121 ºC), and the dielectric constants and loss factors were within the range of published values for orange-fleshed sweetpotato purees. The pilot-scale test runs in a 60 kW microwave unit produced shelf-stable puree packages for >12 months at room temperature. Polyphenolic content of the PFSP purees were evaluated and the results showed that while total phenolics increased (5.9%) and total monomeric anthocyanins slightly decreased (14.5%) with microwave application, antioxidant activity determined by DPPH radical scavenging activity and oxygen radical absorbance capacity (ORAC) assays did not significantly change as a result of microwave processing. Color values showed that microwave processed samples differed from fresh puree in saturation and hue angle, but not in overall color change. PFSP purees increased in gel strength when microwave processed, packaged, and stored, but the gel could be easily disrupted into flowable purees. Overall, high quality retention can be obtained by microwave processing and aseptic packaging of PFSP purees that can be used as functional food ingredients.