Formation of anaerobic products in sweet cherries and their partial release into ambient atmosphere under low oxygen storage

Abstract

Concentrations of acetaldehyde, ethanol and ethyl acetate in the flesh of ripe, sweet cherries were consistently enhanced by very low oxygen conditions in the ambient atmosphere. At the onset of storage the initial concentration of ethanol in the flesh was 6.0 and 6.4 mg l^-1 for the cvs. 'Kordia' and 'Vanda' respectively. After 28 days under anaerobic conditions the concentration in the flesh of cv. 'Kordia' was 5,502 ± 35 mg l^-1, which during the next 10 days of storage in air was increased to 6,476 ± 771 mg l^-1. The production of ethanol under anaerobic conditions increased during the storage period from 101 μg kg^-1h^-1 to 550 μg kg^-1h^-1 from the 16th to the 27th day. The ethanol released from fruit stored at ULO and CA atmospheres was accumulated in the ambient atmosphere at very low concentrations, two orders lower than in the anaerobic atmosphere, at concentrations from 1.2 to 1.6 μg kg^-1h^-1. The concentration of ethyl acetate during the first 10 days under very low oxygen atmosphere did not increase, because biosynthesis practically ceased. At the start it was 0.76 mg l^-1 and after 10 days it had increased to only 0.88 mg l^-1. Until the fruit is exposed to a normal supply of oxygen from the air, there is no change in the esterification rate. Some quantitative relations relate to the production and subsequent release of ethyl acetate from intact fruit, which under subsequent ambient atmosphere storage was detected at very low trace concentrations, of 20 to 80 nl l^-1 overall, for all the different storage regimes.