Sensory impact of three essential oils from the genus Cymbopogon as natural flavorings for fermented yogurt

Essential oils (EOs) used as flavor additives in yogurt are a natural alternative; however, it is essential to conduct sensory tests to determine the appropriate concentrations and thus ensure good product acceptability. The objective of this study was to evaluate the sensory impact of adding three concentrations of EOs from three species of the genus Cymbopogon, C. winterianus (citronella), C. flexuosus (lemongrass), and C. martinii (palmarosa) to yogurt as natural flavorings and aromatics. The yogurt was prepared using reconstituted instant skim milk powder and a commercial starter culture YC-X16 (Chr. Hansen) (4 hours at 40°C). Three concentrations of EOs were also added: 0.02%, 0.01%, and 0.002% w/w. A qualitative focus group analysis was conducted with 8 consumer assessors. For the descriptive analysis, 8 panellists were selected; they were trained and calibrated over four sessions totalling two hours, during which the sensory attributes to be assessed (essence intensity (EI), essence flavour (EF) and yoghurt flavour (YF)) were defined. QDA and Spectrum techniques were combined, using an unstructured linear scale ranging from 0mm (not noticeable) to 150 mm (very intense). For the statistical analysis of the descriptive study, summary statistics, ANOVA and the Tukey test (α = 0.05) were calculated. In the focus group, the flavour enhancers were perceived as best at a concentration of 0.01%. In contrast, the highest concentration (0.02%) was perceived as overpowering in terms of EF. All three EOs were considered products they would consume, but palmarosa was described as the subtlest and lemongrass as the best-tasting additive. In the descriptive analysis, citronella at 0.02% had the highest values for EI (60) and EF (71). At a concentration of 0.01%, no statistically significant differences were observed among the three EOs. In YF, a reduction in intensity was observed with the addition of the EOs, demonstrating a greater effect with citronella. This EOs can be used at lower concentrations to achieve the same intensity as the others. The three EOs evaluated have the potential to enhance the aroma and flavour of yoghurt, which reaffirms that these natural compounds are a good source of aromatic compounds.