engleski

Effect of wheat bran pre-processing on physical properties of 3D-printed snacks

Novel techniques such as 3D printing, enable the creation of snack foods with a tailored nutritional value and structure. The addition of bran for the enrichment of cereal foods with dietary fibre and bioactive compounds is frequently suggested. However, wheat bran contains a high level of polyphenol oxidase (PPO) which is associated with undesirable browning and reduction in antioxidant activity. This study aimed to investigate the influence of high-intensity ultrasound (HIU) (W=400 W, A=100%, t=2 min), vacuum microwave cooking (MW) (W=350 W, t=20 s) and pulsed light field (PL) (t=125 s, 3 pulses/s) processing of wheat bran, on its PPO activity, total phenolic content (TPC) and antioxidant activity (AO), the colour of 3D-printed dough, as well as on the precision and accuracy of 3D printing, and physical properties (colour, height, width, diameter) of baked snacks. TPC (Folin-Ciocalteu Method), AO (FRAP and DPPH), and PPO activity (AACC 22-85) were determined spectrophotometrically. The snack recipe consisted of oat flour, wheat bran (20% at flour basis), pea proteins, sunflower oil, salt, baking soda and water. Ten dough samples were 3D-extruded in the shape of a heart (20 layers) in duplicate using Createbot S3 printer. The 3D-printed shape accuracy and precision of baked samples were determined by digital image analysis, using ImageJ software, as a proportion of white pixels, and calculating the deviation of printed samples from the desired shape. Dough colour difference (ΔE*) between the first and the last printed sample (after 1 h) was determined by measuring lightness, redness, and yellowness using a spectrophotometer. Snacks were baked in a deck oven for 18 min with the lower heater at 140°C and the upper heater at 160°C. Height, line width and diameter of baked snacks, were determined using a calliper. Bran processing with HIU, MW and PL significantly reduced the PPO activity (by 75%, 73% and 65%, respectively), but also TPC and AO compared to unprocessed bran. Among all treatments, HIU processed bran showed highest values for TPC (0.74 ± 0.02 mg GAE/g d.w.) while PL resulted in lowest TPC values (0.59 ± 0.01 mg GAE/g d.w.) but the highest DPPH and FRAP values (1.17 ± 0.01 and 3.63 ± 0.08 μmol Trolox Eq/g d.w, respectively). Dough ΔE* after 1 h was very distinct (3.25). Compared to unprocessed bran, the addition of pre-processed bran resulted in significantly lighter and yellower 3D printed dough, which was darkening slower. In addition, bran pre-processing resulted in higher shape accuracy, while the top and bottom snack diameter were significantly larger when compared with unprocessed bran. Overall, dough with added HIU processed bran was printed with the highest precision (96%), while showing the lowest ΔE* (1.99), whereas PL resulted in the highest shape accuracy (96%) and the lightest snack. We can conclude that wheat bran pre-processing contributes to the physical properties of 3D-printed snack.

High-intensity ultrasound, vacuum microwave cooking, pulsed light, 3D printing precision, dough enzymatic browning

nije evidentirano