As a preliminary step to understand and characterize what metabolites are responsible for the bitter off-favor of Huanglongbing infected fruit, the thresholds of limonin, nomilin, and their combination in a sugar and acid matrix, as well as in healthy ‘Valencia’ orange juice were determined by taste panels. Food grade limonin and nomilin were added alone or in combination to a simple (sucrose and citric acid) or complex (sucrose, glucose, fructose, citric and malic acid) matrix, or were added directly into orange juice. Thresholds were determined by taste panels, composed of 16 to 23 trained panelists, using a three-alternative forced choice (3-AFC) method (ASTM: E-679). In the simple matrix, the threshold of limonin was lower than nomilin. The synergetic effect of limonin and nomilin was significant in decreasing their individual thresholds. Interestingly, the thresholds of limonin and nomilin were lower in orange juice compared to the thresholds measured in the complex matrix. Our current results show that the threshold concentrations of limonin and nomilin when added to healthy ‘Valencia’ orange juice are higher than the concentrations of those compounds measured in juice made with symptomatic HLB fruit, which was perceived bitter by a taste panel. Possibly, the lower sugar and higher acid content of HLB fruit decreased the threshold of those bitter compounds. Moreover, different concentrations of ‘Valencia’ and ‘Hamlin’ HLB infected juice were blended into healthy juice to determine the detection and recognition thresholds. Panelists were able to detect the symptomatic HLB juice at different levels depending on the variety. For both Hamlin and Valencia juices, however, panelists could detect a difference when blending normal juice with 25% HLB symptomatic juice and could describe the difference (bitter, metallic) when normal juice was blended with 50% HLB symptomatic juice. Nomilin was discovered to have a lingering metallic taste that was different from limonin, which was found to be just bitter. This study looked at flavor compounds in juice made from fruit harvested from 15+ trees symptomatic for HLB compared to healthy trees grown in the same area for multiple harvests of Hamlin (December/January, 2009) and Valencia (April/June, 2009). Fruit from HLB symptomatic trees were separated into asymptomatic (normal looking, HLBAS) and symptomatic (small, green and lopsided, HLBS) fruit for comparison to healthy (H) fruit prior to juicing using a JBT extractor/pasteurizer. For Valencia, there were no differences in Brix, but HLB juices tended to have higher titratable acidity (TA), lower ratio (April) and higher oil (June). For Hamlin, Brix was higher in H juice (December), TA higher in HLBS (December), ratio lower in HLBS and oil higher for HLBS juice (December). Healthy juice tended to have higher levels of sucrose and fructose, whereas glucose was variable, especially for HLBS juice. HLB juice had higher levels of citric acid (December Hamlin/April Valencia) but there were no differences for the other two harvests/cultivars. Malic acid tended to be lower in HLB juices. Limonin and nomilin were higher in HLB juices, especially HLBS, but were below reported thresholds. Gas chromatography-olfactometry (GC-O) research did not show differences between H and HLBAS juice, but observed some volatiles that were found either exclusively or at higher aroma intensity in either H or HLBS juices. There were more :green’/ ‘fatty’ aromas in HLBS while there were more ‘sweet’/’fruity’ components in H juices with respect to each other.