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

Abstract

Millet is an unexploited cereal with potential in the food industry due to its nutritional value and resistance to harsh climate conditions. Nutritious millet byproducts have a potential application 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 pretreatment to increase the amount of freely available bioactives from proso millet bran. We also analysed the effect of high intensity ultrasound on enzymatic browning, water retention and protein digestibility, which 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 for 5, 12.5 or 20 min, with the 60, 80 or 100 % amplitude. High intensity ultrasound treatment with 80 % amplitude for 12.5 min improved most significantly the nutritive value; the antioxidant activity measured by FRAP test increased by 15 % (p<0.05), and total phenolic content by 16 % (p<0.05). Still, the impact on the increase of water-soluble and ethanol-insoluble dietary fibre by 38 % was evident after the treatment for 20 min at 100 % amplitude. High intensity ultrasound treatment at 100 % amplitude for 5 min caused the largest improvements in water retention and limited browning of the sample. High intensity ultrasound treatment activated polyphenol oxidase, regardless of the applied heating of the sample. Due to its ambiguous impact on proso millet bran characteristics, the treatment required an optimization, which showed that the optimal pretreatment of a 15 % millet bran suspension in water is at 100 % amplitude for 9.3 min.

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

“…The temperature rise during HIU treatment occurs as a result of a transformation of acoustic to cavitation energy (Mamvura et al, 2018), thus, the acoustic power can be used to describe the HIU treatment (Čukelj Mustač et al, 2019). Our results of the acoustic power ( Figure 2b) was significantly influenced and correlated with the HIU amplitude (r = .99).…”

“…where m is the mass of the sonicated sample (kg), c p is the specific heat capacity of the media (the mixture of water and bran; 3,876.9 J/ kg K -1 ), and dT dt is the increase in temperature (K) over time (s). The predicted specific heat capacity of the bran (c p ) was calculated from its chemical composition according to Čukelj Mustač et al (2019).…”

“…The extraction of free phenolic was performed in triplicates as previously reported (Čukelj Mustač et al, 2019). Sample (250 mg) and 1 ml of 80% ethanol were vortexed (IKA MS 3) in a horizontal position for 10 min, placed into ultrasonic bath (Bandelin Electronic RK 100 H, Sonorex, Berlin, Germany) for 10 min, and centrifuged (MicroCL 21, Thermo Fisher Scientific) at 8,000 rpm for 15 min.…”

“…However, the effect of HIU on the PPO of bran seems cereal dependent since Čukelj Mustač et al (2019) showed that HIU treatment leads to the activation of proso millet bran PPO.…”

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

“…TPC was determined by the Folin-Ciocalteu assay, and antioxidant activity was determined by the ferric reducing antioxidant power (FRAP) and the 2,2′-diphenyl-1-picrylhydrazyl (DPPH) assays according to Čukelj Mustač et al (2019) after extraction of free phenolics in triplicates (Habuš et al, 2021). All measurements were performed on spectrophotometer (Perkin Elmer Lambda UV/Vis/NIR, USA).…”