Characterisation of internal oxygen concentration of strawberry (Fragaria × ananassa) and blueberry (Vaccinium corymbosum).

Gas exchange mechanisms play crucial roles in maintaining fruit post-harvest quality in perishable fruit such as strawberry (Fragaria × ananassa Duch.) and blueberry (Vaccinium corymbosum L.). The internal oxygen concentration ([O2]) of strawberry and blueberry were measured using Clark-type oxygen sensing electrodes. The volume of intercellular voids in strawberry was obtained by micro-computed tomography (micro-CT). In both berries, internal [O2] was consistent and relatively high across measured tissues. The overall [O2] was well above the Michaelis constant (K m) for cytochrome c oxidase in both fruit and different from previously examined grape (Vitis vinifera L.) berry mesocarp with near zero minimum [O2]. In strawberry and blueberry, cell vitality was also maintained at full maturity in the mesocarp. Higher storage temperature (i.e. 20 vs 4°C) reduced internal [O2] of strawberry. Pedicel detachment in blueberry was associated with greater fruit dehydration and lower internal [O2] after short-term storage of 12 h. The results suggest that the intercellular voids of the fruit's mesocarp provide an efficient gas exchange route for maintaining high fruit internal [O2] post-harvest. Understanding the dynamics and factors regulating internal oxygen concentration ([O2]) of strawberry (Fragaria × ananassa Duch.) and blueberry (Vaccinium corymbosum L.) fruit can assist horticultural improvement and post-harvest management. This work has integrated oxygen sensing and non-destructive imaging techniques to provide insight into the 3D microstructure of the mesocarp of strawberries and blueberries. The results provide fundamental knowledge on how oxygen and tissue anatomy are interrelated in small soft fruit. The implications of the observed anatomical features on post-harvest fruit physiology (specifically internal [O2]) are discussed. [ABSTRACT FROM AUTHOR]