Odour and flavour thresholds for key aroma components in an orange juice matrix: esters and miscellaneous compounds

Thresholds for flavour volatiles have been traditionally calculated in water or air but they may vary widely in more complex matrices such as milk, gels or fruit slurries. The data presented are part of a continuing study to provide the industry with threshold guidelines more adequate for the use of flavours in citrus juices. Thresholds of aroma compounds of orange juice (OJ) were determined in reconstituted pump-out (RPO), approaching a deodorized OJ matrix and served at 10-12 degrees C, the temperature at which OJ is consumed. The three-alternative forced choice (3-AFC) method was used (ASTM: E-679). Sixteen to twenty panelists were presented with RPO samples arranged in five rows of three samples corresponding to five spiking levels, each separated by a factor of 3, with a 3-AFC presentation at each level. For each compound, the test was repeated four times. Compounds tested were verified for purity by GC-MS and GC-O. Orthonasal and retronasal thresholds for esters were twice (methyl butanoate) to 30 times (ethyl propanoate) higher in the orange juice matrix than published values in water. The odour activity values (OAVs) of volatile compounds were calculated for two OJs; nine compounds had an orthonasal OAV < 1 when using thresholds determined in RPO, while in contrast, these compounds had an OAV > 1 when calculated with published thresholds determined in water. The relative OAV of some compounds had changed with respect to each other, indicating a different contribution of these compounds to OJ flavour when their OAV was calculated in RPO. These results show the importance of non-water-soluble compounds on odour and flavour perception. The threshold values provided herein are directly usable by the industry, in comparison with the current values published in water, and will help in developing models that would explain OJ flavour based on interactions with the matrix. Copyright (C) 2008 John Wiley & Sons, Ltd.