Fast and accurate quality assessment of Raf tomatoes using NIRS technology

• NIRS was used for measuring quality attributes of Raf tomato.
• Good predictions of color, soluble solids content and titratable acidity were obtained.
• NIRS is suitable for discriminating between tomato ripeness stages.
• The diode array spectrophotometer is a promising tool in online tomato sorting.

Near infrared reflectance (NIR) spectroscopy was used as a fast and accurate technology for the simultaneous measurement of color, sugar and organic acid content in intact Raf tomatoes. The potential of this method coupled with chemometric techniques based on modified partial least squares regression was assessed by comparison with the currently-used traditional method for determining color, dry matter, soluble solid content, glucose, fructose, titratable acidity, malic acid and citric acid. At the same time, the performance of two spectrophotometers, differing primarily in terms of measurement principle and wavelength range, was evaluated. A total of 165 tomatoes (cv. “Raf”) were used in the construction of calibration models for all the parameters previously cited, testing various spectral signal pretreatments. The technology was well suited to sorting Raf tomatoes on the basis of color parameters (a* and a*/b*(r2 = 0.76–0.75; SEP = 2.58–0.09, respectively), soluble solid content (r2 = 0.75; SEP = 0.65%) and titratable acidity (r2 = 0.69; SEP = 0.06%), and useful, though less accurate (r2 < 0.60), for the sorting of fruits by the rest of the color parameters tested (b*, L*), as well as by sugar content (glucose and fructose), dry matter and citric and malic content, particularly when the diode array instrument was used.