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Continuous Flow Microwave-Assisted Processing and Aseptic Packaging of Purple-Fleshed Sweetpotato Purees

Authors

  • L.E. Steed,

    1. Authors Steed, Simunovic, Sandeep, Kumar, Cartwright, and Swartzel are with Dept. of Food, Bioprocessing and Nutrition Sciences, North Carolina State Univ., Raleigh, NC 27695-7624, U.S.A. Author Truong is with U.S. Dept. of Agriculture, Agricultural Research Service, South Atlantic Area, Food Science Research Unit, North Carolina State Univ., Raleigh, NC 27695-7624, U.S.A. Direct inquiries to author Truong (E-mail: Den.Truong@ars.usda.gov).
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  • V.-D. Truong,

    1. Authors Steed, Simunovic, Sandeep, Kumar, Cartwright, and Swartzel are with Dept. of Food, Bioprocessing and Nutrition Sciences, North Carolina State Univ., Raleigh, NC 27695-7624, U.S.A. Author Truong is with U.S. Dept. of Agriculture, Agricultural Research Service, South Atlantic Area, Food Science Research Unit, North Carolina State Univ., Raleigh, NC 27695-7624, U.S.A. Direct inquiries to author Truong (E-mail: Den.Truong@ars.usda.gov).
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  • J. Simunovic,

    1. Authors Steed, Simunovic, Sandeep, Kumar, Cartwright, and Swartzel are with Dept. of Food, Bioprocessing and Nutrition Sciences, North Carolina State Univ., Raleigh, NC 27695-7624, U.S.A. Author Truong is with U.S. Dept. of Agriculture, Agricultural Research Service, South Atlantic Area, Food Science Research Unit, North Carolina State Univ., Raleigh, NC 27695-7624, U.S.A. Direct inquiries to author Truong (E-mail: Den.Truong@ars.usda.gov).
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  • K.P. Sandeep,

    1. Authors Steed, Simunovic, Sandeep, Kumar, Cartwright, and Swartzel are with Dept. of Food, Bioprocessing and Nutrition Sciences, North Carolina State Univ., Raleigh, NC 27695-7624, U.S.A. Author Truong is with U.S. Dept. of Agriculture, Agricultural Research Service, South Atlantic Area, Food Science Research Unit, North Carolina State Univ., Raleigh, NC 27695-7624, U.S.A. Direct inquiries to author Truong (E-mail: Den.Truong@ars.usda.gov).
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  • P. Kumar,

    1. Authors Steed, Simunovic, Sandeep, Kumar, Cartwright, and Swartzel are with Dept. of Food, Bioprocessing and Nutrition Sciences, North Carolina State Univ., Raleigh, NC 27695-7624, U.S.A. Author Truong is with U.S. Dept. of Agriculture, Agricultural Research Service, South Atlantic Area, Food Science Research Unit, North Carolina State Univ., Raleigh, NC 27695-7624, U.S.A. Direct inquiries to author Truong (E-mail: Den.Truong@ars.usda.gov).
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  • G.D. Cartwright,

    1. Authors Steed, Simunovic, Sandeep, Kumar, Cartwright, and Swartzel are with Dept. of Food, Bioprocessing and Nutrition Sciences, North Carolina State Univ., Raleigh, NC 27695-7624, U.S.A. Author Truong is with U.S. Dept. of Agriculture, Agricultural Research Service, South Atlantic Area, Food Science Research Unit, North Carolina State Univ., Raleigh, NC 27695-7624, U.S.A. Direct inquiries to author Truong (E-mail: Den.Truong@ars.usda.gov).
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  • K.R. Swartzel

    1. Authors Steed, Simunovic, Sandeep, Kumar, Cartwright, and Swartzel are with Dept. of Food, Bioprocessing and Nutrition Sciences, North Carolina State Univ., Raleigh, NC 27695-7624, U.S.A. Author Truong is with U.S. Dept. of Agriculture, Agricultural Research Service, South Atlantic Area, Food Science Research Unit, North Carolina State Univ., Raleigh, NC 27695-7624, U.S.A. Direct inquiries to author Truong (E-mail: Den.Truong@ars.usda.gov).
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  • Paper nr FSR08-10 of the Journal Series of the Dept. of Food, Bioprocessing and Nutrition Sciences, North Carolina State Univ., Raleigh, N.C. 27695-7624, U.S.A. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Dept. of Agriculture or North Carolina Agricultural Research Service, no does it imply approval to the exclusion of other products that may be suitable.

Abstract

ABSTRACT:  Pumpable purees from purple-flesh sweetpotatoes (PFSP) were subjected to microwave heating using a 60 kW, 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 915 MHz microwave system to measure dielectric in-line properties and examine the puree temperature profiles. The results demonstrated uniformity in heating of the puree at sterilization temperatures (>121 °C), 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 stable 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 2,2-diphenyl-1-picrylhydrazyl (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 so that they can be used as functional food ingredients.

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