Colour training and colour differences thresholds in orange juice

• A specific training for a panel to evaluate orange juice colour is proposed.
• Commercial orange juices were evaluated instrumentally and visually.
• Instrumental colour measurements and visual evaluation were correlated.
• The colour attribute intensity correlated significantly with chroma and lightness.
• Difference colour threshold was 1.5 and 2.8 units for trained and untrained panel.

This study was aimed at training a panel of assessors to evaluate specifically orange juice colour, and to establish the colour difference threshold in orange juice for a trained and untrained panel. Panellists were first preselected using Farnsworth–Munsell 100-Hue Test and then trained with a specific method for orange juice colour. This training allowed assessors to evaluate visually orange juice samples in hue and intensity. The final selection of assessors was a panel of 8 trained observers with reproducibility and repeatability, and a significant discrimination among the samples (p < 0.05).On the other hand, commercial orange juices were evaluated both instrumentally by image analysis and visually by the trained panel, and the untrained panel. Instrumental colour measurements and visual evaluation were correlated. Values around 1.5 and 2.8 CIELAB units could be consider the threshold for colour differences between two orange juices for the trained and untrained panel, respectively.