Non-destructive assessment of the internal quality of intact persimmon using colour and VIS/NIR hyperspectral imaging

- Persimmon astringency can be assessed by hyperspectral imaging and chemometrics.
- Colour ratios obtained from images best correlated with fruit firmness.
- Internal quality control by different non-destructive VIS-NIR instruments.
- Easy applicability of non-destructive technique in quality or chemical analysis.

The internal quality of intact persimmon cv. 'Rojo Brillante' was assessed trough visible and near infrared hyperspectral imaging. Fruits at three stages of commercial maturity were exposed to different treatments with CO2 to obtain fruit with different ripeness and level of astringency (soluble tannin content). Spectral and spatial information were used for building classification models to predict ripeness and astringency trough multivariate analysis techniques like linear and quadratic discriminant analysis (LDA and QDA) and support vector machine (SVM). Additionally, flesh firmness was predicted by partial least square regression (PLSR). The full spectrum was used to determine the internal properties and later principal component analysis (PCA) was used to select optimal wavelengths (580, 680 and 1050 nm). The correct classification was above 92% for the three classifiers in the case of ripeness and 95% for QDA in the case of astringency. A value of R2 = 0.80 and a ratio of prediction deviation (RPD) of 1.86 were obtained with the selected wavelengths for the prediction of firmness which demonstrated the potential of hyperspectral imaging as a non-destructive tool in the assessment of the firmness, ripeness state and astringency level of 'Rojo Brillante' persimmon.