The quality of the green fraction of leaf protein concentrate from Chenopodium quinoa Willd. grown at different levels of fertilizer nitrogen

Abstract

Chenopodium quinoa Willd. was grown at fertilizer nitrogen application of 150, 260, 470 and 880 kg per ha. Green fractions of leaf protein concentrate (LPC) were obtained from expressed plant juice using heat fractionation. An increase of the fertilizer level up to 470 kg N ha −1 resulted in higher dry matter yield and true protein content in plants. A further increase of the nitrogen level was ineffective. The LPC contained about 60% of protein. There were no major differences in amino acid composition of proteins extracted from plants fertilized with increasing doses of nitrogen, except for a reduced leucine content and a slight increase of cystine content. The biological value of protein estimated with rats by the Thomas—Mitchell balance method increased with increased N-fertilizer level, but the true digestibility was constant for all preparations. Addition of polyethylene glycol (PEG) 4000 to unfractionated leaf protein concentrate from C. quinoa had an adverse effect on its nutritional value.