Quinoa leaves as a source of soluble proteins: Extraction and proteomic characterization from four different varieties of Chenopodium quinoa

This work assessed four varieties of quinoa leaves, two grown in Ireland and two in Chile, as endogenous sources of soluble proteins. The four leaf protein extracts, obtained using mild extraction conditions, had different nutrient compositions, with protein contents ranging from 53 ± 2 to 63 ± 2 %. The protein extract from variety quinoa Zeno (Ireland) presented the lowest content of chlorophyll, 0.09 ± 0.03 %, and phenolic compounds, 113 ± 8 mg_GA/g, which resulted in the highest solubility, above 90 % at pH ≥5. The protein profile characterized by MALDI-TOF-TOF confirmed the presence of RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) in all the extracts, which contained most of the essential amino acids. Only extract from quinoa Zeno met FAO (2011) recommendations for essential amino acids, consistent with greater content of RuBisCO, while the other extracts had limited sulphur-containing amino acids. Quinoa leaves have the potential to become an alternative source of protein for food applications with good nutritional value.