Microstructure analysis and detection of mealiness in ‘Forelle’ pear (Pyrus communis L.) by means of X-ray computed tomography

• Defects in mealy pear macrostructure were visualised with macro X-ray CT.
• Less dense zones were observed in the neck of mealy pears, also before ripening.
• Micro-CT confirmed mealy tissues contain more pores larger than 56.53 μm.
• Larger and oval shaped cells were observed in mealy fruit.
• Evidence of lysigenous pore formation in mealy fruit was found.

Mealiness causes fruit to develop a soft and dry texture during ripening. No technique currently exists to detect mealiness non-destructively. Two studies were conducted to i) determine the potential of X-ray macro computed tomography (macro-CT) to detect mealiness in ‘Forelle’ pear (Pyrus communis L.) non-destructively, and to ii) establish histological differences between mealy and non-mealy fruit using X-ray micro computed tomography (micro-CT). Scans were made after 8 and 11 weeks of cold storage at −0.5 °C and at the end of shelf life of 7 days. Total porosity, pore size distribution and connectivity of cells were measured on regions of interest (ROI) cubes excised from the neck and equator of individual fruit. Macro-CT scans showed the presence of structural disorders in the cortex tissue, identified by micro-CT as large pores, in mealy fruit. These pores were already present at the end of cold storage before fruit would become mealy. Statistical differences with fruit which would ripen and become juicy were significant (P < 0.05). The disorder appeared more clearly in the neck than in the equator region of the cortex. At the end of shelf life, porosity was significantly higher in mealy than non-mealy fruit. Micro-CT results confirmed that tissues of mealy fruit were more porous than those of non-mealy fruit, with a larger proportion of pores greater than 56.53 μm. Evidence was found of lysigenous pore formation in mealy fruit. Cells of mealy fruit were larger and oval-shaped while non-mealy fruit cells were more spherical. X-ray computed tomography was shown to be a promising technology for the non-destructive determination of mealiness at an early stage.