Nitrogen Fertilization Influences Protein Nutritional Quality in Red Head Chicory

Excess nitrogen fertilization of leafy vegetables may cause undesirable accumulation of nitrates and a decrease in essential amino acids, resulting in a decrease in protein nutritional quality. We investigated the effect of nitrogen (N) fertilization (0, 100 or 200 kg N ha-1) on the nutritional quality of red head chicory proteins. Lysine limited biological value of proteins in the control (0 N) as well as fertilized samples. The lysine content and protein biological value according to Mitchell and Block method decreased significantly (p 0.05) with 100 and 200 kg ha-1 nitrogen applied relative to control. The Oser's essential amino acid index and protein biological value were relatively high and did not decrease with increased N fertilization. The correlation between the protein biological value of red head chicory and crude protein levels was negative (p 0.001). Protein nutritional quality was optimal for adults and lower than optimal for children aged 2-5 and 10-12 years.