Influence of ethylene on carotenoid biosynthesis during papaya postharvesting ripening

The carotenoid composition was evaluated during ripening of papaya cv. 'Golden' under untreated (control) conditions and treated with ethylene and 1-methylcyclopropene (1-MCP). At the end of the experiments, the total carotenoid content in the control group (2194.4 μg/100 g) was twice as high as that found in ethylene (1018.1 μg/100 g) and 1-MCP (654.5 μg/100 g) gas-treated samples. Separation of 21 carotenoids by HPLC connected to photodiode array and mass spectrometry detectors showed that no minor carotenoids seemed to be particularly favoured by the treatments. Lycopene was the major carotenoid in all untreated and gas-treated samples, ranging from 461.5 to 1321.6 μg/100 g at the end of the experiments. According to the proposed biosynthetic pathway, lycopene is the central compound, since it is the most abundant carotenoid indicating a high stimulation of its upstream steps during ripening, and it is the source for the synthesis of other derivative compounds, such as β-cryptoxanthin. The influence of both gas treatments on the carotenoid biosynthetic pathway was considered.