## 3 Results
With concentrations above their odour thresholds, this research confirms the importance of the analysed odorants for the orange odour. Especially, limonene [21; 22; 23] showed concentrations drastically above its odour threshold. The \(\alpha\)-terpineol concentration was below its odour threshold throughout the whole storage period and might therefore not contribute to the sensory properties of oranges. In contrast to the bananas, the storage time did not significantly affect the concentrations and no ripening effect was observed. This is in line with the non-climacter properties of the oranges [4]. Instead, the concentrations varied over time and, as in the case of the banana odorants, showed high standard deviations that corresponded to the natural variations of the odorant concentrations in the oranges. Interestingly, the hexanal concentrations increased at the end of the storage period. Concerning a possible effect of ozone on the odorant concentrations, no significant differences were observed between the samples treated with ozone and the control samples, with the exception of hexanal, whose concentration on day 11 was significantly higher in the ozone-treated sample than that of the control sample. As in the case of the odorants in the bananas, no clear trend was observed in the oranges between the samples with and without ozone treatment. Thus, it was concluded that the applied ozone exposition had no impact on the odour properties of the oranges. In addition to the selected key odorants, the total titratable acidity was measured (Figure 3, Table S5). The total acid concentration determined as malic acid decreased during storage in the bananas, which is in line with the findings of [PERSON] and [PERSON] [30]. In contrast to the bananas, the total acid concentration determined as citric acid remained relatively stable in the oranges. The total titratable acidity was not significantly affected by the ozone treatment in both bananas and oranges, and only slight differences were observed between the control samples and those treated with ozone. The weight loss was higher for bananas than for oranges (Figure 4). The bananas had only around 80% of their initial weight at the end of the storage, while the oranges maintained over 93% of their weight at the same point in time. However, no significant differences were observed in bananas with respect to weight loss between the control samples and those treated with ozone. The weight loss in oranges was by trend higher for the samples treated with ozone, but the differences were only significant on day 7. This could be an indication of an impact of ozone on the weight loss in oranges, which has to be verified with more intense ozone treatments. These data show that the applied ozone treatment did not affect important quality parameters, such as key odorants, total acid concentration, and weight loss, neither in oranges nor in bananas. In addition, it was investigated whether the ozone treatment had a positive impact on the shelf life by inhibiting mould growth on the fruits. On bananas, only the growth of _P. expansum_ was slightly reduced. The growth of the other moulds applied was not affected. On oranges, ozone did not affect the growth of any mould tested. Impact of Three Ozone Treatments per Day on Odour-Active Compounds, Total Titractable acidity, Ascorbic Acid, Weight Loss, and Mould Growth  
In a second experiment, a higher ozone exposition per day was tested. In this case, the same settings as during the first experiment were applied, with the exception of three ozone treatments per day instead of one. Consequently, the ozone exposition was tripled. In addition to the previously analysed parameters, ascorbic acid was analysed as a further quality parameter regarding the impact of ozone on vitamins. The odorant concentrations in the bananas during storage are summarized in Figure 5 and Table S3.