Steed L E, Truong V-D, Simunovic J, Sandeep K P, Kumar P, Cartwright G D, Swartzel K R
Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Raleigh, NC 27695-7624, USA.
J Food Sci. 2008 Nov;73(9):E455-62. doi: 10.1111/j.1750-3841.2008.00950.x.
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 degrees 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.
将紫肉甘薯（PFSP）制成的可泵送泥状食品通过一个60千瓦、915兆赫的连续流动系统进行微波加热，随后在柔性容器中进行无菌包装，以获得一种货架期稳定的产品。最初的测试运行使用一个5千瓦、915兆赫的微波系统来测量在线介电性能并检测泥状食品的温度分布。结果表明，在杀菌温度（>121摄氏度）下泥状食品的加热均匀，介电常数和损耗因子在已发表的橙肉甘薯泥状食品数值范围内。在一个60千瓦微波装置中进行的中试规模测试运行生产出了在室温下稳定的货架期稳定的泥状食品包装。对PFSP泥状食品的多酚含量进行了评估，结果显示，虽然微波处理后总酚含量增加了（5.9%），总单体花青素含量略有下降（14.5%），但通过2,2-二苯基-1-苦基肼（DPPH）自由基清除活性和氧自由基吸收能力（ORAC）测定的抗氧化活性并未因微波处理而显著变化。颜色值表明，微波处理的样品在饱和度和色相角方面与新鲜泥状食品不同，但在整体颜色变化方面没有差异。PFSP泥状食品在经过微波处理、包装和储存后凝胶强度增加，但凝胶可以很容易地被打散成可流动的泥状食品。总体而言，通过对PFSP泥状食品进行微波处理和无菌包装可以实现高品质保留，从而使其能够用作功能性食品成分。
