An attempt to find a non-destructive method to determine ripeness of kiwifruit (Actinidia chinensis Planch. 'Jintao')

Actinidia chinensis Planch. 'Jintao' was successfully introduced to the Iberian market. Commercially harvested 'Jintao' kiwifruit need to be ripened before consumption to develop desirable texture and flavor. Ripeness determination is based mainly on soluble solids content (SSC) and firmness measured using destructive methods. The objective of this work was to find a non-destructive methodology to determine ripening stage. Measurements of SSC (°Brix), firmness, titratable acidity, dry matter, weight loss and ethylene production were taken for every fruit at two harvest dates and through storage at ambient temperature for 20 days. Complementary non-destructive visible/near-infrared (Vis/NIR) interactance spectroscopy was also performed. The results showed that firmness decreased rapidly after 10 days. SSC increased through storage and reached up to 18%. Dry matter and titratable acidity changed very little during storage. Autocatalytic ethylene production started after 13-14 days and the peak value was higher in fruit from the first harvest than those from the second harvest. The interactance spectra showed good correlation with SSC, fair correlation with firmness and no significant correlation with titratable acidity, pH and dry matter. It was concluded that SSC may be assessed non-destructively through Vis/NIR spectroscopy, while more research is needed to establish the feasibility of measuring firmness, dry matter and titratable acidity using Vis/NIR methods.