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Influence of particle size reduction and high-intensity ultrasound on polyphenol oxidase, phenolics and technological properties of wheat bran

Wheat bran is a by-product rich in bioactive compounds but possess a strong polyphenol oxidase (PPO) activity, which can act undesirably on product quality. This study aimed to optimize the particle size (500, 255, 10 µm) of wheat bran and time and amplitude of high- intensity ultrasound (HIU) treatment on the PPO activity, total phenolics, antioxidant activity, and water swelling using response surface methodology. The PPO activity decreased depending on the particle size and HIU treatment time. Phenolic content, antioxidant activity and swelling were dependent on bran particle size. Temperature rise, depending on the HIU time and amplitude, affected PPO, phenolics and antioxidants. In optimized conditions (particle size 10 µm, HIU 15 min), 93% of bran PPO was inactivated while phenolic content increased for 11%. Wheat flour combined with micronized and ultrasonically treated bran (at 20% w/w) had improved gluten formation and pasting properties compared with flour containing native bran.

high-intensity ultrasound, wheat bran, polyphenol oxidase, cryomilling, response surface methodology

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