Apple (Malux ×domestica Borkh., cv. Fuji) fruit were harvested from two California orchards 190 and 210 days after full bloom and from an additional three orchards at 190 days after full bloom. Fruit were immediately exposed to 20 or 50 kPa CO2 in air at 20 °C. Area of flesh browning and tissue ethanol, acetaldehyde, and ethyl acetate concentrations for individual fruit were determined immediately before exposure and after 3 and 7 days (20 kPa) or 1 and 3 days (50 kPa) exposure to CO2. Area of flesh browning and concentrations of all compounds increased with increasing duration of exposure to high CO2, were greater in response to 50 kPa than to 20 kPa CO2, and were greater for fruit harvested later in the season. For individual orchards and for individual fruit within most orchards, greater flesh browning was associated with higher acetaldehyde concentrations after 7 days exposure to 20 kPa CO2 or 3 days exposure to 50 kPa CO2. Similarly, flesh browning was positively correlated with ethanol concentrations after 7 days at 20 kPa CO2, but was not related to tissue ethyl acetate concentrations at either CO2 partial pressure. However, higher production of ethanol, acetaldehyde, or ethyl acetate relative to flesh browning occurred during exposure to 50 kPa than to 20 kPa CO2. This suggests that the relationship between accumulation of these compounds and CO2-induced flesh browning in `Fuji' is not simply causal.
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