“Enhancing quinoa (Chenopodium quinoa Willd) protein extraction: Alkaline solubilization coupled to isoelectric precipitation effects on structure, digestibility and antinutrients”

Abstract

Quinoa (Chenopodium quinoa Willd) has gained popularity as a plant-based protein source due to its high protein content and complete amino acid profile. However, protein extraction methods such as alkaline solubilization coupled to isoelectric precipitation (ASIP), can affect protein structure, digestibility, nutritional quality, and the composition of antinutritional factors. This study aimed to assess the effects of ASIP on the secondary structure, protein quality and antinutritional factors (ANFs) composition from three quinoa varieties. The results showed that quinoa protein isolates exhibited a decrease in random coil structures, while β-turns and β-sheets increased, as indicated by FTIR analysis. In vitro protein digestibility improved after protein extraction, ranging from 82.12% to 84.50%. The amino acid score ranged from 0.67 – 0.88, with Yellow quinoa protein concentrate exhibiting the highest value. Black quinoa protein isolate showed the lowest total oxalate content (105.00 mg/100g), while Red quinoa protein concentrate presented higher levels of phytic acid (2.0 g/100 g), saponins (150.0 mg/g), and total phenolic compounds (161.5 mg GAE/100g). Notably, gluten content decreased in all samples following protein extraction. Despite the presence of certain ANFs in quinoa protein isolates/concentrates, the protein quality of quinoa isolates and concentrates was not adversely affected. In conclusion, the extraction process reduced several ANFs, including lectins, oxalates, and gluten, while enhancing the overall protein quality.