A remote acceptance probe and illumination configuration for spectral assessment of internal attributes of intact fruit

Near infrared spectroscopy can be employed in the non-invasive assessment o f intact fruit for eating quality attributes such as soluble solid content (SSC). Rapid sorting is dependent on a suitable non-contact geometry of fru it, light source and detector assembly, optimized for a given fruit commodi ty. An optical system was designed with reference to distribution of SSC an d light penetration into rockmelon fruit. SSC of mesocarp tissue was not si gnificantly different over the greater part of the proximal-distal axis of the fruit, particularly in the vicinity of the fruit equator. There was als o no consistent variation in SSC of mesocarp tissue with respect to radial position of sampling. Mesocarp SSC was higher (similar to3% w/v) closer to the seed cavity. The optical sampling system was therefore designed to asse ss an equatorial position on the fruit. Light penetrating a rockmelon fruit was empirically assessed to be diffuse at a depth of <15 mm from the fruit surface. Signal decreased in an exponential proportionality with depth int o the fruit, but was still detectable at depths in excess of the seed cavit y of rockmelons. A partial transmittance optical design was employed, with a collimated light source interrupted by a central light stop, and a detect or viewing the shadowed region of the sample. This system did not physicall y contact the sample. It was compared to a system with a light excluding 'c ontacting' shroud between the detector and the fruit surface. The performan ce of calibrations generated using the non-contact configuration was not si gnificantly different than for the configuration requiring contact.