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Influence of High Intensity Ultrasound Treatment on Bioactive Compounds in Buckwheat and Pumpkin Seed Cake Flour

High intensity ultrasound is a robust, green and rapid technology that has potential in releasing bioactive compounds from whole grains. Buckwheat is an example of alternative crop of high nutritional and antioxidative potential. Similarly pumpkin seed cake, a byproduct of oil production, is rich in proteins (51%), minerals and bioactive compounds. It is usually utilized as animal feed but is also suitable for human consumption. Its potential is especially evident in glutenfree industry, where in combination with a nutritious glutenfree cereal such as buckwheat could result with innovative, sustainable, nutrient dense glutenfree products. However, polyphenols of seed cakes are enclosed in hard and insoluble fiber like structures and cell wall components. This research aimed to determine the effect of high intensity ultrasound treatment (400W power probe; 100% amplitude; 5, 10, 20 minutes) on the release of bioactive components of pumpkin seed cake and buckwheat flour. We wanted to test which of the twofold ultrasound effects would be prevailing: improvement in release of antioxidants from a cell wall due to cell swelling, or the generation of free radicals due to intensity of the cavitation reaction. Balance between these two effects was determined through the free phenolic content (HPLC and FolinCiocalteu method), antioxidant activity (DPPH and FRAP), and unsaturated fatty acid composition (GCFID). Ten minutes high intensity ultrasound treatment had an optimal effect on buckwheat flour, causing 13 and 65% increase in antioxidant activity (DPPH and FRAP), and 24% increase in total phenolic content (TPC). The treatment of buckwheat flour caused a significant decline of only C22:1 (from 0.23% to 0.18% and 0.16% after 10 and 20 minutes, respectively) and C16:1 which dropped from 0.35% to 0.25% after 10 minute treatment. Ultrasound treatment had in general negative effect on pumpkin seed cake flour, decreasing the antioxidant activity and TPC, although a significant increase of pcoumaricacid was noticed under all ultrasonic conditions. The observed antioxidant activity decrease could be result of antioxidant protection of unsaturated fatty acids, which generally stayed unchanged during ultrasound treatment. A small decline from 0.15% to 0.12% was determined only for C20:1 after 5 minutes ultrasound treatment. Future work will examine how to optimize the exploit of pumpkin seed cake flour bioactives in glutenfree bakery industry.

high intensity ultrasound ; buckwheat ; pumpkin seed cake ; antioxidant activity ; unsaturated fatty acids ; free phenolics

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