Correlation between visual and instrumental colour measurements of orange juice dilutions: effect of the background

The colour of 21 ultrafrozen orange juice samples was measured by spectroradiometry. Each sample was diluted with distilled water to obtain eight levels of concentration (10%, 25%, 40%, 50%, 60%, 75%, 90% and 100% of juice). Measurements were made against both a white and a black background. The results showed that the colour parameters which best correlated with orange juice concentration were different depending on the background used. The correlation between sensory and instrumental measurements was also evaluated. The mixtures were classified by 12 panellists in two cabins, one with white walls and the other one with black walls. These visual assessments revealed that the usage of a cabin with black walls led to better classifications of the samples as a function of their concentration.