Content of Free Amino Acids in Onion ( Allium cepa L.) as Influenced by the Stage of Development at Harvest and Long-term Storage

The changes in free amino acid (FAA) composition during long-term storage of onions ( Allium cepa L.) were investigated over a 3 year period. The influence of development at the time of harvest on the FAA composition of onions was investigated over a 2 year period. In addition, the composition of FAA in different morphological parts was analysed over a 1 year period. The most abundant amino acids were arginine and glutamine. The results indicated that the later the onions were harvested the lower the content of almost all the FAA in the dry matter. These differences in content were maintained throughout long-term storage. The percentage of FAA in the dry matter increased in relation to the centrality of leaves in the bulb but was independent of storage time.