Prediction of apple firmness from mass loss and smunkage

Prediction of firmness from mass loss and shrinkage was investigated in apples (Malus x domestica Borkh.) under regular atmosphere (RA) storage conditions. Apples ('Delicious' and 'Fuji') were repeatedly weighed to determine mass loss. Shrinkage was measured with a strain gauge sensor. 'Delicious' apples lost firmness (73 to 58 N) while 'Fuji' apples maintained firmness at 69 N over 57 days in storage. Apples lost mass at a constant rate with 'Delicious' losing mass slower (0.6% per month) than 'Fuji' (1.1% per month). 'Delicious' apple shrank less (0.28 mm) than the 'Fuji' (0.70 mm) over 57 days. The relationship between firmness and mass loss, or shrinkage was dependent on apple cultivar. Firmness was significantly and linearly related to mass loss and to shrinkage in 'Delicious' apples. It is possible to predict firmness of 'Delicious' apples under RA storage conditions by tracking mass loss or shrinkage.