Controlled atmosphere-induced changes in pH and organic acid metabolism may affect color of stored strawberry fruit

Skin and flesh of 'Selva' strawberries (Fragaria x ananassa Duch.) stored at 5 degrees C in air or 2 kPa O-2 became darker red and accumulated anthocyanin levels, but these changes were reduced in fruit stored in air + 20 kPa CO2, 2 kPa O-2 + 20 kPa CO2, 0.5 kPa O-2, and 0.5 kPa O-2 + 20 kPa CO2 (balance N-2 in all CA treatments). Increasing pH and decreasing titratable acidity in tissues during storage, especially in the internal tissues, were more marked in fruit stored in high CO2 atmospheres. Since pH affects color expression of the anthocyanin pigment, these changes may contribute to the observed changes in color. Combined citric and malic acid concentrations were higher in the external tissues (10.6 mg g(-1)) than internal tissues (5.5 mg g(-1)), and decreases in concentration of both acids were greater in fruit kept in high CO2 atmospheres. Succinic acid in fruit tissues was present in low concentrations, but usually increased in high CO2 atmospheres. (C) 1999 Elsevier Science B.V. All rights reserved.