Non-destructive determination of impact bruising on table olives using Vis–NIR spectroscopy

Bruise damage on table olives is the main factor that reduces fruit quality and leads to a severe loss of product during harvesting and postharvest handling operations. The Manzanilla cultivar is the most important table olive variety and it is also very susceptible to the formation of bruises. In this study, visible and near-infrared spectroscopy techniques were used to detect bruise damage on fruit with different absorbed impact energy levels (low = 13 ± 2 mJ, medium = 27 ± 2 mJ and high = 58 ± 7 mJ). The visible spectral region of 535–680 nm was used to distinguish between undamaged and damaged fruit for qualitative analysis. The greater differences in reflectance in the near-infrared region of 700–950 nm enabled a good quantitative analysis by distinguishing between the different impact energy levels. Modified partial least square models were developed to determine the bruise volume in damaged fruits and the absorbed energy during impact. Good fits (r2 = 0.87–0.90) were obtained between the values predicted by visible and near infrared spectroscopy and the values measured in laboratory by the reference methods for bruise volume and absorbed impact energy.

► Bruise damage on table olives is highly related to the absorbed impact energy. ► Colour changes on bruised fruits are detected in the visible region of 535–670 nm. ► Degree of fruit damage is detected in the NIR region of 700–950 nm. ► Quantitative analysis of table olive bruises is possible using Vis–NIR spectroscopy. ► Bruise volume and impact energy on damaged fruit is predicted by MPLS models.