Assessment of Yellow-fleshed Kiwifruit (Actinidia chinensis ‘Hort16A’) Quality in Pre- and Post-harvest Conditions Using a Portable Near-infrared Spectrometer

Abstract

Dry matter content (DM), soluble solids content (SSC), and flesh hue (FH) are important quality attributes of yellow-fleshed kiwifruit (Actinidia chinensis ‘Hort16A’). Rapid non-destructive measurement tools enable effective assessment of quality attributes in the field or in packhouses and offer the potential for selective harvesting and differential postharvest treatments. This study investigates a few practical issues for use of one such tool, a portable near-infrared spectrometer, the FANTEC™ FQA-NIRGUN. Experimental results indicated that the precision of the NIRGUN in predicting the DM, SSC and FH of ‘Hort16A’ kiwifruit, given as the root mean square error of calibration (RMSEC), is 0.6%, 0.9% and 1.4°, respectively, and is similar to that reported for standard laboratory benchtop spectrometers. These levels of precision are good enough to distinguish differences in fruit quality between fruit from different vines. However, this is only possible when measurements are carried out under similar conditions either within a short period of time in the field when fruit temperature is stable or in a temperature-controlled laboratory. The calibration developed on one instrument could be transferred to another instrument, but bias correction is necessary after the calibration transfer. Hence, the absolute accuracy of predictions from the NIRGUN is limited by significant and variable bias offset issues, particularly for field measurements when fruit are on the vine.