Rye and Oat crispbread improvement with biologically active substances from plant by-products

Abstract

Vegetable processing in food industry results in significant number of by-products - peel, mark, bark, seeds still rich in bioactive compounds. The objective of this study was to investigate the stability of total phenolic content (TPC) and antioxidant activity after high temperature short time (HTST) extrusion cooking of a rye and oat- based matrix with addition of apple, carrot and pumpkin by-product flour (BPF) in various amounts (5%, 10%, 15% and 20%). Extrusion was performed with co-rotating twin-screw extruder (compression ratio 8:1) at Ltd MILZU. The main drive of extruder was provided with a 7.5 HP motor (400 V, 3 HP, 50 cycles). Temperatures for extrusion zones were 125 °C /135 °C /145 °C. TPC was determined using the Folin Ciocalteu method. Antioxidant activity was evaluated by free radical 2, 2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant scavenging activity. TPC in cereal-based crispbread was 62.03 ± 0.15 mg GAE g -1 DW before extrusion and 37.73 ± 1.96 mg GAE g -1 DW after extrusion. Addition 20% of apple BPF increased TPC in crispbread to 193.92 ± 1.37, carrot BPF 171.36 ± 6.97 and pumpkin BPF to 195.09 ± 4.68 mg GAE g -1 DW after extrusion. Antioxidant activity of control (20% oats, 80% rye flour blends) sample was 0.516 ± 0.192 mg TE g -1 DW but in samples with addition of 20% by-products, it was significantly higher reaching 0.926 ± 0.05 TE g -1 DW in samples with pumpkin by-products after extrusion.