INFLUENCE OF HIGH-INTENSITY ULTRASOUND ON BIOACTIVE COMPOUNDS OF BUCKWHEAT HULLS

Buckwheat hulls are by-products of the milling industry with a potential to be used as a functional food or in pharmaceutical preparations. The main advantage of hulls is their high dietary fibre and bioactive compound content, which have numerous positive health effects. This study aimed to investigate the effect of high-intensity ultrasound (400 W, 24 kHz) on the extractability of free bioactive compounds, antioxidant activity, water swelling and activity of enzyme polyphenol oxidase of buckwheat hulls milled to a particle size of <= 56 mu m. A 10% aqueous suspension of buckwheat hulls with different initial temperatures (9.7; 20.0; 45.0; 70.0 or 80.4 degrees C) was treated (2.9; 5.0; 10.0; 15.0 or 17.0 min) by direct immersion of the ultrasonic probe (d = 22 mm) at 100% amplitude following a central composite design. In comparison to the control sample, it was found that high-intensity ultrasound treatment increased the content of total phenolic compounds, antioxidant activity, water swelling and polyphenol oxidase activity. Optimum treatment conditions should be defined depending on the intended application of the treated hulls in cereal foods production.