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

Abstract

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, and 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% wt/wt) had improved gluten formation and pasting properties compared with flour containing native bran. Practical applications Consumers show a growing awareness of health benefits of whole wheat and highfiber foods. Bran is a by-product of milling industry with a great potential as a functional food ingredient. However, the enzymatic browning of bran containing products that occur during processing worsens their sensory properties, nutritional value, and consumers' acceptance. Currently, new technologies such as micronization and ultrasound treatment are getting more attention in cereal processing. This study showed that the combined micronization and high-intensity ultrasound treatment can successfully inactivate the polyphenol oxidase (up to 93%) from wheat bran, and thus, prevent the enzymatic browning. Also, treated bran can be successfully incorporated up to 20% to wheat flour with lesser disruption of the gluten formation and pasting properties when compared with the native bran. The findings of this study contribute to better future usages of wheat bran in food applications adding the sustainability of cereal chain. How to cite this article: Habuš M, Novotni D, Gregov M, et al. Influence of particle size reduction and high-intensity ultrasound on polyphenol oxidase, phenolics, and technological properties of wheat bran.

Influence of Flour Type, Dough Acidity, Printing Temperature and Bran Pre-processing on Browning and 3D Printing Performance of Snacks

“…PPO activity was determined according to the method AACC 22-85.01 (AACC, 2000), as described by Habuš et al (2021), by measuring the absorbance of the reaction mixture at 475 nm over a period of 1 h, and is expressed as the mean of the absorbance of two replicates. The activity unit (U) for PPO is defined as an increase in absorbance of 0.001 per min per gram of bran.…”

“…Cereal products containing wholemeal flour or bran are susceptible to enzymatic browning over time (Hidalgo et al, 2013;Niu et al, 2014). Bran possesses high polyphenol oxidase (PPO) activity (Habuš et al, 2021), which catalyses the formation reaction of o-quinons in the presence of molecular oxygen, resulting in undesirable browning (Fan et al, 2020;Niu et al, 2014;Pathare et al, 2013;Pellicer et al, 2018;Zhang et al, 2019). PPO activity can be controlled by pH, temperature and processing (Ghazal et al, 2019;Habuš et al, 2021;Niu et al, 2014;Yadav et al, 2010).…”

“…Bran possesses high polyphenol oxidase (PPO) activity (Habuš et al, 2021), which catalyses the formation reaction of o-quinons in the presence of molecular oxygen, resulting in undesirable browning (Fan et al, 2020;Niu et al, 2014;Pathare et al, 2013;Pellicer et al, 2018;Zhang et al, 2019). PPO activity can be controlled by pH, temperature and processing (Ghazal et al, 2019;Habuš et al, 2021;Niu et al, 2014;Yadav et al, 2010). The addition of reducing agents can reduce the discolouration of barley dough (Quinde-Axtell et al, 2006).…”

“…Therefore, various thermal and non-thermal processing techniques that can inactivate PPO are being developed. Recently, high-intensity ultrasound (HIU) was proved to effectively reduce PPO activity of wheat bran (WB) (Habuš et al, 2021), vegetables (Fan et al, 2020;Zhang et al, 2019) and fruit (Costa et al, 2013;Rodríguez et al, 2015). Furthermore, microwave cooking effectively inactivates PPO in barley (Sharma & Gujral, 2011), pear snacks (Devi et al, 2021), apple juice (Siguemoto et al, 2018) and strawberry purée (Marszałek et al, 2015), while pulsed light (PL) treatment can inactivate PPO of fungi (Pellicer et al, 2018) and pineapple juice (Vollmer et al, 2020).…”

Processing, chemical signature and food industry applications of Camellia sinensis teas: An overview

“…Thus, the time and temperature used in the process must be strictly controlled during the process. High pressure assisted freezing ( Cheng, Zhu, & Sun, 2021 ) and high-intensity ultrasound ( Habuš et al, 2021 ) may be alternatives for the denaturation of PPO, reducing damage to the concentration of polyphenols. The residual content of this oxidase in teas can also be inhibited by ultra-high pressure ( Chen et al, 2021 , Chen et al, 2021 ).…”