Digital Image Analysis and Visual Evaluation of Orange Juice: Influence of Different Measurements' Conditions

This study assesses the effect of background, surrounding, thickness and dilutions on the colour specifications of orange juice (OJ) analyzed by digital image and visual evaluation. A commercial OJ was diluted with distilled water to give ten levels of concentration (100, 90, 80, 70, 60, 50, 40, 30, 20 and 10 % of juice). These samples were evaluated instrumentally by digital image analysis using nine combinations of surroundings and backgrounds (black, grey and white) and three different thicknesses. Visual evaluation was also carried out on black, grey and white backgrounds. A grey surrounding, a white background and a fixed thickness are suggested to be used in future measurements of OJ colour by digital image analysis. Results of visual evaluation indicated that panellists were able to order correctly the OJ samples according to the dilution level, independently of the background chosen. The correlations between the instrumental and the visual analysis were significant (p < 0.05) in all the backgrounds explored.