Porosity quantification in pear fruit with X-ray CT and spatially resolved spectroscopy

Hypoxia-related disorders in apple and pears such as browning have been associated with insufficient transport of respiratory gasses inside the fruit during controlled atmosphere (CA) storage. Tissue porosity affects gas exchange and, hence, fruit respiration. It might, therefore, be interesting to adapt the storage conditions to the porosity of the fruit, especially in the case of low-porosity fruit like pears, which are highly susceptible to browning disorders. To improve the current CA storage strategies in that direction, fast, non-destructive measurement of fruit porosity is required. To this end, X-ray CT-based porosity maps and spatially resolved spectroscopy (SRS) were used to characterize respectively the porosity and optical properties of intact pear cultivars (Pyrus communis L.), including 'Thimo', 'Cepuna', and 'Conference'. Thereafter, the link between the fruit porosity and light-scattering properties was investigated. The porosity of the tissue region from the fruit surface down to 3 mm deep as well as the spatially averaged porosity of intact pears from 3 cultivars were found to be linearly correlated to the reduced scattering coefficient (mu(s')) at 760 nm and 835 nm calculated from SRS measurements. Both 'Cepuna' and 'Conference' pears showed similar porosities and scattering levels, which were slightly higher than those observed for 'Thimo' pears. The presented results suggest the possible application of laser scatter imaging at 760 nm and 835 nm for fast, contactless and non-destructive assessment of pear porosity.