Analysis and modelling of firmness and juiciness of peaches, subjected to chilling injury

Nectarine fruit after cool storage soften normally, but become sometimes dry instead of juicy. An experiment was conducted to see if time resolved reflectance spectroscopy (TRS) could distinguish this internal disorder non-destructively. The optical parameter of absorption coefficient μa at 670 nm of nectarine (Prunus persica 'Morsiani 90') was measured at harvest and used to sort the fruit in 15 batches so that each batch had a similar range of fruit maturity according to the value of μa at 670 nm. Fruit were stored at 20°C after harvest or after 30 days of storage at 0 or 4°C. Each day for 5 days during shelf life one batch of 30 fruit per treatment was examined both non-destructively (TRS) and destructively (firmness and expressible juice). Modelling of the data found that fruit softening could be expressed by an exponential model for fruits from all conditions. The effect of cold storage on softening during subsequent shelf life is minimal, with a small increase in softening rate in fruit treated at 4°C. During ripening extractable juice increased in unstored fruit and decreased in stored fruit. Extractable juice was not related to μa at 670 nm. Rearranging data according to the probelation technique, the development of juiciness in stored and unstored fruit could be described by an exponential model.