2018 ASHS Annual Conference

The concentrations of free amino acids in the peel and pulp of banana (Musa L. spp., AAA group, Cavendish subgroup. ‘Valery’) fruit during ripening at 20 °C were studied. A high-throughput method combining high performance liquid chromatography (HPLC) with multiple reaction monitoring (MRM) of selected mass spectra ions were used to quantify amino acids at seven distinct ripening stages as defined by measures of internal ethylene, O₂, and CO₂ concentrations, aroma volatile emissions, and peel color. Volatile production commenced two days after the peak in ethylene production and a day following the climacteric peak in internal CO₂. The maximum rate of branched-chain ester synthesis occurred two to three days days after its onset. Production of 2-propyl and 3-methylbutyl esters was much higher in the pulp compared to the peel, confirming that the pulp rather peel is the primary site of banana aroma synthesis. Of the 20 amino acids measured, only leucine, valine, and cysteine increased concomitantly with ester formation. This was observed in the pulp, but not in the peel. The data support the role of the metabolic pathways for valine and leucine in the formation of, respectively, 2-methylpropyl and 3-methylbutyl esters. There was a slight peak in the formation of several amino acids in the pulp (e.g., alanine, arginine, asparagine, glutamine, and methionine) coinciding with the climacteric peak in CO₂, but a similar pattern was not seen for the peel. These data are the first to demonstrate distinct differences in amino acid metabolism in the peel and pulp of banana related to their role in ripening and aroma biosynthesis.