Changes in acetaldehyde, ethanol and amino acid concentrations in broccoli florets during air and controlled atmosphere storage

Acetaldehyde, ethanol and non-protein bound amino acids were determined in broccoli florets (Brassica oleracea L. var. Italica cv. Marathon) stored for 7 days at 10 degreesC in air or controlled atmospheres (0.125, 0.25, or 0.5% O-2 alone or in combination with 20% CO2, or 20% CO2 in N-2) followed by 2 days aeration. Floret yellowing was visible at days 7 and 9 in air. Low O-2 or low O-2 plus high CO2 atmospheres delayed yellowing. Acetaldehyde and ethanol concentrations increased as O-2 concentrations decreased with or without 20% CO2. Aeration for 2 days generally reduced acetaldehyde and ethanol concentrations. The total free amino acid concentration increased during air-storage from 244 mu mol g(-1) dry weight at harvest to 573 ymol g(-1) dry weight at day 9. Due to severe soft rot development in the broccoli treated with 0.125 and 0.25% O-2 free amino acids were only determined in samples treated with 0.5% O-2, 0.5% O-2 + 20% CO2 and 20% CO2. Amino acid change in samples stored under 0.5% O-2 were similar to those of air-stored broccoli. Storage for 7 days in the CO2-containing atmospheres resulted in an increase in non-protein amino acids and a decrease in protein amino acids, although total amino acid content remained the same. Alanine accumulated in 0.5% O-2 or 20% CO2 in N-2 atmospheres. The non-protein amino acid, gamma -aminobutyrate accumulated in 20% CO2 but its concentration decreased upon aeration, and these changes were associated with similar but opposite changes in glutamate concentrations. Aspartate content also decreased in 20% CO2 and increased upon aeration, This coincided with the formation of an unidentified amino acid. In broccoli treated with high CO2 atmospheres, alpha -decarboxylation seemed to be an important path of metabolic interconversion, however, these reaction pathways were reversible upon aeration. (C) 2001 Elsevier Science B.V. All rights reserved.