Phophorous nuclear magnetic resonance (31P-NMR) spectroscopy was used to study the vacuolar and cytoplasmic pH and the inorganic phosphate (Pi) pool distribution in `Fino de Jete' cherimoya (Annona cherimola Mill.) fruit stored at a chilling temperature (6 °C). Fruit stored at the ripening temperature (20 °C) for 3 days were used as a control. 31P-NMR results confirmed that 6 °C storage caused cytoplasmic acidosis (a decrease of 0.72 ± 0.08 pH units) and a notable increase in the amount of Pi in the cytoplasm. Spectra of perchloric acid extracts also revealed that storage at 6 °C was associated with an increase in the total amount of Pi and phosphorylated metabolites. Moreover, perfusion experiments with a phosphate medium confirmed the preferential accumulation of Pi in the cytoplasm in chilled tissues. Specific activation of phosphoenolpyruvate carboxylase (PEPC) (32.1 ± 1.7 μmol·min-1·mg-1) was observed in those fruit. In chilled fruit the amount of ADP was held at steady-state levels and ATP levels increased, contrary to observations for ripe fruit, where the pool of total nucleotides decreased beyond the point of NMR detection. Fruit stored at 6 °C exhibited a low respiration rate, but metabolism was not arrested and an increase in total soluble solid contents was also observed.
Quality changes of little tuna fillet (Euthynnus affinis) during chilling temperature storage
