Articles
NON-DESTRUCTIVE QUALITY MEASUREMENTS OF APPLES BY MEANS OF NIR-SPECTROSCOPY
In Belgium, the optimal picking time is predicted every year based upon different quality tests.
Because many of these tests are either subjective (for example colour and taste) or time consuming to measure (for example soluble solids and acid determination), there is a demand for an objective, fast and non-destructive assessment of the quality of the apples.
The objective of this contribution was to evaluate the use of NIR reflectance spectroscopy as a tool to measure quality attributes of the apples such as soluble solid contents, acidity, starch index and firmness in the context of optimal picking time determination.
Soluble solids, acidity, starch index and firmness were measured on 255 apples of the varieties Jonagold, Golden Delicious, Elstar, Cox’s Orange Pippin, and Boskoop at different dates before the picking date.
Of each apple, 4 spectra were recorded and averaged.
The maturity age of the apples was correlated with the spectra and resulted in very high correlations, which indicate that the NIR-technology is very well capable to determine the internal quality differences in time.
More precise models, like for soluble solid content, starch content and acidity were also very satisfactory with high validation correlations.
At last, a good correlation was obtained between the Streif-index, which is an indication for the picking time, with the spectra.
The results indicate that it is possible to use the NIR spectroscopy as a non-destructive technique for measuring internal apple quality.