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Optimisation of High Intensity Ultrasound Treatment of Proso Millet Bran to Improve Physical and Nutritional Quality

Millet is an unexploited cereal with potential in the food industry due to its nutritional value and resistance to harsh climate conditions. Nutritious millet by-products have a potential to be exploited in the development of functional cereal products, but require processing in order to improve their physical and nutritional quality. Therefore, we investigated high intensity ultrasound as a pre-treatment for increasing the amount of freely available bioactives from proso millet bran. We also investigated high intensity ultrasound effect on enzymatic browning, water retention and protein digestibility, that are crucial for the utilization in the bakery and pasta industry. A 15 % millet bran suspension in water was treated with 400 W ultrasound probe during 5, 12.5, or 20 min, with the 60, 80, or 100 % of amplitude. High intensity ultrasound treatment with 80 % amplitude during 12.5 min showed the most significant improvement of the nutritive value ; – the antioxidant activity measured by FRAP test increased by 15 % (p < 0.05), total phenolic content by 16 % (p < 0.05). Still, the impact on the dietary fibre soluble in water and not ethanol, was Food Technology and Biotechnology 57 (2) 2019 www.ftb.com.hr Please note that this is an unedited version of the manuscript that has been accepted for publication. This version will undergo copyediting and typesetting before its final form for publication. We are providing this version as a service to our readers. The published version will differ from this one as a result of linguistic and technical corrections and layout editing. evident after the 100 % amplitude and 20 min treatment, causing a rise by 38 %. High intensity ultrasound treatment of 100 % amplitude and 5 min caused largest improvements in water retention and limited browning of the sample. Polyphenol oxidase was activated by high intensity treatment, regardless of the applied heating of the sample. Ambiguous impact of high intensity ultrasound on proso millet bran characteristics required an optimization which showed that the optimal pre-treatment for a 15 % millet bran suspension in water is at 100 % amplitude during 9.3 min.

antioxidant activity, enzymatic browning, high intensity ultrasound, millet bran, water retention

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