Recovery and evaluation of chloroplast-free protein concentrates from leaves of Chenopodium quinoa and Atriplex hortensis grown in Sweden and Australia

Abstract

Yields and nutritive quality of protein fractions separated from genetically identical plant material (Atriplex hortensis and Chenopodium quinoa) grown under 2 different agricultural conditions in 2 geographically distant locations (Sweden and Australia) were compared, and reasons for the existing differences were studied. Optimum growth stage at which plants should be used for most efficient protein extraction was established as 14 wk for A. hortensis and 15 wk for C. quinoa for both planting locations. Also, optimum conditions of protein fractionation process for A. hortensis extracts were established (45degrees C at pH 5.75 for recovery of chloroplast-containing fraction, followed by precipitation of chloroplast-free fraction [food-grade fraction] at 80degrees C) from the point of view of yield and quality of recovered food-grade protein fraction. Protein concentrates recovered under optimum fractionation conditions were nutritionally equal to casein, with the 3 essential amino acids methionine, lysine and tryptophan (both total and available) being at levels exceeding FAO/WHO standards.