Ripeness Prediction in Table Grape Cultivars by Using a Portable NIR Device

Abstract

In the past years, near infrared (NIR) spectroscopy has been applied to the agricultural industry as a non-destructive tool to predict quality parameters, e.g., ripeness of fruit, dry matter content, and acidity. In two years, 2019 and 2020, berries of four table grape cultivars (Cotton Candy™, Summer Royal, Allison™, and Autumncrisp®) were collected during the season to obtain spectral measurements and quality data for developing predictive models based on NIR spectroscopy to be practically used in the vineyard. A SCiO™ sensor was used in 2019 for predicting the ripening parameters of Cotton Candy™; in particular, total soluble solids (TSS) (R2 = 0.95; RMSE = 0.60, RPD = 13.13), titratable acidity (R2 = 0.97; RMSE = 0.40, RPD = 7.31), and pH (R2 = 0.96; RMSE = 0.07, RPD = 26.06). With these promising results, in the year 2020, the above-mentioned table grape cultivars were all tested for TSS prediction with successful outcomes: Cotton Candy™ (R2 = 0.97; RMSE = 0.68, RPD = 7.48), Summer Royal (R2 = 0.96; RMSE = 0.83, RPD = 7.13), Allison™ (R2 = 0.97; RMSE = 0.72, RPD = 8.70) and Autumncrisp® (R2 = 0.96; RMSE = 0.60, RPD = 9.73). In conclusion, a rapid and economic sensor such as the SCiO™ device can enable a practical application in the vineyard to assess ripening (quality) parameters of table grapes. Thus, this device or similar ones can be also used for a fast sorting and screening of quality throughout the supply chain, from vineyard to cold storage.

Keywords

• NIR spectroscopy
• PLSR
• table grape
• TSS
• acidity
• optical sensor