Metabotype Dynamics of Market-Ripe Orange (Citrus sinensis) During Postharvest Ageing at Room Temperature

Objectives: To develop and apply a robust method using NMR-based metabolic phenotyping to characterise the metabolic changes occurring in commercially acquired, market-ripe orange (Citrus sinensis—a non-climacteric fruit) during postharvest ageing. Methods: Orange juice was obtained at different postharvest timepoints, based on morphological changes in the fruit (e.g., days 9, 30, and 35). The fruits were stored at room temperature (26 °C) and 60% relative humidity, throughout the study. The NMR spectra of the juice were collected and analysed using a semi-targeted approach alongside multivariate, correlation, and entropy analyses. Results: A robust method to assess the orange juice metabotype was developed with a total of 42 metabolites, of which two were unknowns, including phenolic compounds, carbohydrates, amino acids (essential, conditionally essential and non-essential), alcohols, and other metabolites that may have direct nutritional value. This method proved to be useful to monitor the progressive metabotype complexity derived from postharvest deterioration. Based on metabolite patterns across postharvest stages, correlation structures, and entropy values, the ageing and advanced-ageing metabotypes were defined at days 30 and 35, respectively. Conclusions: Phlorin, galacturonate, succinate, rhamnose and prolinebetaine were associated with ageing profiles, providing a basis for their potential use in targeted monitoring of orange postharvest ageing. These findings could support the future development of compact, affordable devices for rapid in situ assessment of postharvest ageing status, with potential benefits of supporting the preservation of product quality, nutritional and economic values.