In GreenCHAINge fruit & vegetables, non-destructive measurement techniques are explored and developed. The general aim is to measure quality aspects non-destructively, objectively, repeatable and reliably. One of those measurement methods is by using NIR. In this subproject, NIR measurements of kiwi are explored.
Experiment and Results
More than 350 kiwifruits were stored at 20 °C. The kiwis were measured using a SCIO portable NIR (reflectance mode) spectrometer. Each kiwi was measured with and without skin. Firmness, determined with a penetrometer, and Brix measurements were taken as reference (ground truth).
Correlation matrix of NIR measurement with Brix and Firmness measurements
|R2 measured on Flesh
|R2 measured on Skin
|0.745 ± 0.036
|0.564 ± 0.055
|0.553 ± 0.054
|0.440 ± 0.053
The prediction (R2) of the Brix and Firmness was improved by removal of the skin. The skin of kiwi suppresses reliable non-destructive measurements of internal quality characteristics like Brix and firmness.
The SCIO portable NIR can better predict firmness and brix based on measurements on the flesh than measurements on the skin.