Near infrared light penetration in watermelon related to internal quality evaluation.

The interaction between near infrared (NIR) light and the sample is a key factor to take into consideration when developing applications using NIR spectroscopy. The aim of this study was to assess the penetration depth of the NIR light through both intact watermelons and the red flesh of the cut fruit, using an interactance NIR system. The results showed a maximum penetration of between 9 and 11 mm in the assays carried out on intact watermelons and 11 mm in the watermelon flesh. The prediction performance of the different NIR system configurations used were compared by quantifying the SSC in intact watermelons in a non-destructive way. The results obtained for the assay in which the illuminated regions were separated by 28 mm (Distance 4) reported the best results for determination of SSC (%) obtaining an R2 cv = 0.73 and RMSECV = 0.39 % and an R2 p = 0.81 and RMSEP = 0.30 % when the set of data for that distance was split into calibration and internal validation sets. • The penetration depth of NIR light into different watermelons tissues was studied. • The penetration depth of NIR light was assessed using MCR-ALS. • The optimum optical measurement geometry of the NIR system was identified. • Penetration depth through the rind of the watermelon was about 9–11 mm. • NIR interactance spectroscopy was used to measure the SSC in intact watermelons. [ABSTRACT FROM AUTHOR]