‘Hort16A’ (Actinidia chinensis Planch. var. chinensis) is a yellow-fleshed kiwifruit cultivar that is marketed globally as ZESPRI® GOLD kiwifruit. SSC at harvest is an indicator of fruit maturity, and DM content reflects the potential SSC at “eating ripe,” i.e., when starch reserves in the berry have been converted to sugars during fruit softening. FH is an important quality parameter for ‘Hort16A’, because its yellow color is a primary factor in the appeal of the fruit to the consumer (Martin and Luxton, 2005). Flesh color changes from green to yellow as the fruit matures. However, there is still a considerable degree of variability present in the properties of the fruit at harvest (Schaare and Fraser, 2000).
Fruit variability at harvest leads to problems in post-harvest handling. For example, 1 of 2 weeks of conditioning at 5 °C is used for fruit with FH values above 105°. This enables the flesh degreening process to occur but can result in excessive softening of fruit with FH below 103°. A line of fruit may have a mix of FH. Thus, identification of fruit with lower FH (which are generally associated with more advanced maturity) in the orchard, coupled with staged selective harvesting of the mature fruit, would lead to reduced variation in quality and overall improvement in the quality of the harvested crop. In addition, the ready identification of poorly performing or slowly maturing vines would enable targeted remedial measures to be undertaken.
Near-infrared (NIR) spectroscopic tools suitable for orchard use would enable fast, non-destructive, and effective monitoring of fruit maturity on-vine. The color and taste attributes of ‘Hort16A’ are currently determined in the New Zealand kiwifruit industry by destructive measurement of FH, DM, and SSC. Laboratory-based NIR spectroscopy on samples of ‘Hort16A’ kiwifruit post-harvest has demonstrated that it is possible to measure these attributes with prediction errors of ≈0.5%, 0.9%, and 1.1° for DM, SSC, and FH, respectively (Clark et al., 2004). Portable NIR instruments have been developed and used to assess maturity and quality indices of many fruits (Aoki et al., 2010; Costa et al., 2002; Golding et al., 2006; Khuriyati et al., 2004; Kusumiyati et al., 2008; Saranwong et al., 2003a, 2003b; Zude et al., 2008). However, the performance of these instruments under different temperature and light conditions has not been studied rigorously for in situ measurements of ‘Hort16A’ kiwifruit in the field.
The study reported here evaluated the performance of a commercially available FQA-NIRGUN released by the FANTEC Research Institute (Shizuoka, Japan) with an attempt to determine possible influences of temperature and light conditions. The possibility of transferring predictive models developed on one NIRGUN to another NIRGUN was also tested.
Clark, C.J., McGlone, V.A., De Silva, H.N., Manning, M.A., Burdon, J. & Mowat, A.D. 2004 Prediction of storage disorders of kiwifruit (Actinidia chinensis) based on visible-NIR spectral characteristics at harvest Postharvest Biol. Technol. 32 147 158
Costa, G., Noferini, M., Fiori, G. & Miserocchi, O. 2002 Determination of indications of harvest and fruit quality in kiwifruit Rivista di Frutticoltura e di Ortofloricoltura 64 20 23
Feng, J., Maguire, K.M. & MacKay, B.R. 2002 Effects of package and equilibration time on physiochemical attributes of ‘Hayward’ kiwifruit Acta Hort. 599 149 155
Golding, J.B., Satyan, S., Liebenberg, C., Walsh, K. & McGlasson, W.B. 2006 Application of portable NIR for measuring soluble solids concentrations in peaches Acta Hort. 713 461 464
Khuriyati, N., Matsuoka, T. & Kawano, S. 2004 Precise near infrared spectral acquisition of intact tomatoes in interactance mode J. Near Infrared Spectrosc. 12 391 396
Kusumiyati, T., Akinaga, M., Tanaka, & Kawasaki, S. 2008 On-tree and after-harvesting evaluation of firmness, color and lycopene content of tomato fruit using portable NIR spectroscopy J. Food Agr. Environ. 6 327 332
McGlone, V.A., Jordan, R.B., Seelye, R. & Martinsen, P.J. 2002 Comparing density and NIR methods for measurement of kiwifruit dry matter and soluble solids content Postharvest Biol. Technol. 6 191 198
Montefiori, M., McGhie, T.K., Hallett, I.C. & Costa, G. 2009 Changes in pigments and plastid ultrastructure during ripening of green-fleshed and yellow-fleshed kiwifruit Sci. Hort. 119 377 387
Saranwong, S., Sornsrivichai, J. & Kawano, S. 2003a Performance of a portable NIR instrument for Brix value determination of intact mango fruit J. Near Infrared Spectrosc. 11 175 181
Saranwong, S., Sornsrivichai, J. & Kawano, S. 2003b On-tree evaluation of harvesting quality of mango fruit using a hand-held NIR instrument J. Near Infrared Spectrosc. 11 283 294
Schaare, P.N. & Fraser, D.G. 2000 Comparison of reflectance, interactance and transmission modes of visible-near infrared spectroscopy for measuring internal properties of kiwifruit (Actinidia chinensis) Postharvest Biol. Technol. 20 175 184
Zude, M., Pflanz, M., Kaprielian, C. & Aivazian, B.L. 2008 NIRS as a tool for precision horticulture in the citrus industry Biosystems Eng. 99 455 459