Impact of sensory interactions among volatile compounds of juice of Red Delicious apples

We obtained volatile aroma compounds from the juices extracted from three different Red Delicious apple ( Malus domestica ) varieties, which included esters, alcohols, and aldehydes. Among these compounds, ethyl 2-methylbutanoate, methyl 2-methylbutanoate, ethyl butanoate, ethyl hexanoate, hexanal, and butyl 2-methylbutanoate showed high odour active values in the juices. Four compounds (ethyl 2-methylbutanoate, ethyl octanoate, ethyl butanoate, and ethyl hexanoate) were selected to investigate possible interactions occurring in the apple juices. The results demonstrated that the additions of these four aroma volatile compounds could decrease the threshold and intensity of the sensory notes of the solutions compared to those without the addition of these compounds. Lastly, ethyl 2-methylbutanoate was added to the solutions to investigate interactions with σ–τ function. Here, σ represents the ratio of the aroma intensity of the mixed solution to the sum of aroma intensities of all compounds in the solution before blending. The τ represents the aroma of the mixture ratio between the mixture and the sum of aroma compounds before mixing. The results clearly indicated that additive or synergistic effects occurred among these volatiles at sub-threshold concentrations.