Non-invasive detection of russet on pome fruit by a luster sensor

Russeting (i.e., suberinisation of the fruit peel) changes the physical features of the fruit surface. Affected fruit peel on apple or pear fruit becomes rough and brown, which is associated with changes in light reflection. The objective of the present project was to examine two new technologies as to their suitability for non-destructive determination of russet occurrence. These were a) an industrial luster sensor (type CZ-H72, Keyence, Japan) and b) a new type of a 3D colour microscope (type VHX 5000). Fruit examined by three-dimensional colour microscopy (200×magnification) showed that russet increased peel roughness by ca. 2.5-fold from ca. 20 µm to ca. 50 µm on russet fruit sections. Russet peel showed significantly reduced luster, with smaller variation than russet-devoid peel. These results indicate that this sensor-based russet detection may also be employed for other fruit or skin disorders.