Changes in acetaldehyde, ethanol and amino acid concentrations in broccoliflorets 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 fo r 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 b y 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 a nd ethanol concentrations increased as O-2 concentrations decreased with or without 20% CO2. Aeration for 2 days generally reduced acetaldehyde and et hanol concentrations. The total free amino acid concentration increased dur ing 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 s amples treated with 0.5% O-2, 0.5% O-2 + 20% CO2 and 20% CO2. Amino acid ch ange in samples stored under 0.5% O-2 were similar to those of air-stored b roccoli. Storage for 7 days in the CO2-containing atmospheres resulted in a n 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, gamm a -aminobutyrate accumulated in 20% CO2 but its concentration decreased upo n aeration, and these changes were associated with similar but opposite cha nges in glutamate concentrations. Aspartate content also decreased in 20% C O2 and increased upon aeration, This coincided with the formation of an uni dentified amino acid. In broccoli treated with high CO2 atmospheres, alpha -decarboxylation seemed to be an important path of metabolic interconversio n, however, these reaction pathways were reversible upon aeration. (C) 2001 Elsevier Science B.V. All rights reserved.