Free amino acid composition in primary and secondary inflorescences of 11 broccoli (Brassica oleracea var italica) cultivars and its variation between growing seasons

Abstract

Eleven broccoli cultivars were grown in the field in spring/summer (April–July) and summer/winter (September–January). Free amino acid composition was determined by HPLC in primary and secondary inflorescences separately. A total of 17 amino acids were identified: L-alanine (Ala), L-arginine (Arg), L-asparagine (Asn), L-aspartic acid (Asp), glycine (Gly), L-glutamic acid (Glu), L-glutamine (Gln), L-histidine (His), L-isoleucine (Ile), L-leucine (Leu), L-methionine (Met), L-phenylalanine (Phe), L-serine (Ser), L-threonine (Thr), L-tryptophan (Trp), L-tyrosine (Tyr) and L-valine (Val). The major amino acid was L-glutamine, which represented on average between 39.5% (in cvs Durango and Green Valiant) and 55.5% (in cv Shogun) of the total amino acid content among cultivars, followed by L-glutamic acid with a variation between 12.1% (in cv Shogun) and 17.4% (in cv Marathon). A few amino acids represented less than 1% each (Gly, Leu, Met, Phen, Thr, Trp and Tyr). For most of the amino acids there were significant differences between cultivars, whilst only a few amino acids showed significant variations between inflorescences. Season also induced significant differences in the content of most of the identified amino acids. The cultivar with the highest total free amino acid content (323.9 mmol kg−1 DW) on average of both seasons (391.3 in spring/summer and 256.4 in summer/winter) was Shogun, whilst the others were above the minimum of 177.3 mmol kg−1 DW found in cv SK3. There was a general tendency for higher total amino acids levels in spring/summer than in summer/winter, but it was clear that this effect was dependent on the cultivar. © 2000 Society of Chemical Industry