Fermented quinoa flour: Implications of fungal solid-state bioprocessing and drying on nutritional and antioxidant properties

Quinoa (Chenopodium quinoa Willd) is a pseudocereal rich in protein and excellent source of vitamins, antioxidants, and minerals. Developing new quinoa-based products would be a strategy to extend its consumption. The aim of this study is to evaluate the impact of solid-state fermentation with Pleurotus ostreatus and drying (hot-air at 50, 60 and 70 °C and lyophilization) on the nutritional and functional properties of fermented white and black quinoa flours. Changes in proximal composition revealed that white variety was more suitable for solid-state fermentation (SSF), according to the higher biomass production, higher increase of protein (2.11%) and insoluble fiber (7.82%) content. SSF was highly effective in phytic acid reduction (90%) regardless the variety. However, after fermentation, quinoa seeds presented reduced total phenolic content (TPC) and antioxidant capacity, especially on black variety. Nonetheless, hot-air drying improved the antioxidant properties (increased TPC and antioxidant capacity) and promoted changes in the phenolic profile. These changes were characterized by a release of gallic acid together with a notable reduction of vanillic, caffeic and ferulic acids, quercetin-3-glucoside and/or quercetin. A notable increase of the angiotensin converting enzyme-I inhibitory activity was found on the fermented flours mainly due to SSF.