Influence of firmness measurements by dehydration and ripening depends on both measurement device and fruit type

Increasing energy prices are leading to reduced storage of produce. Consequently, increased amounts of produce are stored at suboptimal temperatures for extended amounts of time, resulting in accelerated loss of fruit firmness. Simplified, the main processes leading to loss of fruit firmness are fruit ripening-related loss in tissue structure and dehydration-related loss of turgor, both of which are accelerated under suboptimal storage conditions. Classically, ripening-related loss of firmness is assessed using Magness-Taylor type firmness determination using a penetrometer. However, since this measurement is destructive and thus cannot be applied on every fruit, non-destructive alternatives have been developed, using acoustic, impact, deformation, compression and NIR-based technologies, among others. While available devices using these technologies have been validated for ripening-related losses in firmness, little is known about the sensitivity of the underlying technologies to fruit dehydration. This work assesses the influence of ripening and dehydration on multiple 'non'-destructive firmness measurement devices in both blueberry and pear. Firmness was measured using durometer, impact devices, acoustic, limited compression and Magness-Taylor based technologies. Different technologies differed in their dependency on dehydration and ripening. Furthermore, their dependency on dehydration and ripening also differed between blueberry and pear. Strategies to separate dehydration and ripening-related firmness are discussed for different fruit.