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Fresh and aged coconut water (CW) samples were introduced directly into the electrospray ionisation (ESI) source, and were combined with the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) technique to characterise in situ chemical compounds produced during natural ageing (from 0 to 15 days) at room temperature (23 °C). The ESI-FT-ICR MS readings were acquired and the data were correlated to conventional methodologies: pH, total titratable acidity (TA), total soluble solids, microbial analyses, and ultraviolet visibility (UV-vis) spectroscopy analysis. In general, the pH and TA values changed after 3 days of storage making the CW unsuitable for consumption. The ESI(-)-FT-ICR data also showed a clear and evident change in the chemical profile of CW after 3 days of ageing in the m/z 150-250 and 350-450 regions. Initially, the relative intensity of the natural markers (the m/z 215 and 377 ions-sugar molecules) decreases as a function of ageing time, with the last marker disappearing after 3 days of ageing. New chemical species were then identified such as: citric (m/z 191), galacturonic (m/z 193), gluconic (m/z 195), and saccharic (m/z 209) acids. ESI(-)-FT-ICR MS is a powerful tool to predict the physicochemical properties of CW, such as the pH and TA, where species such as fructose, glucose, sucrose, and gluconic acid can be used as natural markers to monitor the quality of the fruits.

Some bacterial species can colonize humans and plants. It is almost impossible to prevent the contact of clinically pathogenic bacteria with food crops, and if they can persist there, they can reenter the human food chain and cause disease. On the leaf surface, microorganisms are exposed to a number of stress factors. It is unclear how they survive in such different environments. By increasing adhesion to diverse substrates, minimizing environmental differences, and providing protection against defence mechanisms, biofilms could provide part of the answer. Klebsiella pneumoniae subsp. pneumoniae is clinically important and also associated with fruit diseases, such as “pineapple fruit collapse.” We aimed to characterize biofilm formation and adhesion mechanisms of this species isolated from pineapple in comparison with a clinical isolate. No differences were found between the two isolates quantitatively or qualitatively. Both tested positive for capsule formation and were hydrophobic, but neither produced adherence fibres, which might account for their relatively weak adhesion compared to the positive control Staphylococcus epidermidis ATCC 35984. Both produced biofilms on glass and polystyrene, more consistently at 40°C than 35°C, confirmed by atomic force and high-vacuum scanning electron microscopy. Biofilm formation was maintained in an acidic environment, which may be relevant phytopathologically.

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