WINETECH Technical Yearbook 2020

FIGURE 2. Results from the 3D surface plots look at the interaction between two thiols at the time.

> 34 < 34 < 32 < 30 < 28 < 26 < 24

> 28 < 28 < 26 < 24 < 22 < 20 < 18

2a

2b

FIGURE 1. Experimental layout of Experiment 2.

Interactions are often explained in terms of synergisms and masking effects as can easily be illustrated looking at figure 2c and 2d. The attribute represented in those two plots is ‘blackcurrant’, very often associated with 4MMP. The pattern followed by the interaction of 3MH x 4MMP (figure 2c) highlights a maximum synergistic effect once the first compound is added at medium concentration and the second one at high concentrations. In this case 1 + 1 = 3, since the intensity of this particular fruit note is surely higher than the simple sum of the two. In the case of 3MHA x 4MMP, the interaction is much more complicated. A synergism happens at the highest con­ centrations of both compounds and the intensity of ‘blackcurrant’ is amplified. On the contrary, once the additions are at medium levels, a masking effect comes

Secondly, the results fromthe 3D surface plots look at the interaction between two thiols at a time, but from a single attribute perspective. It is very interesting to notice how increasing concentrations of a specific compound do not necessarily result in a linear increase in their associated aroma intensity. Consider the descriptor ‘red berries’ for instance. When comparing the surface plots of 3MH x 4MMP and 3MHA x 4MMP (figure 2a and 2b) we can clearly see an opposite behaviour. At level zero for 4MMP, a linear increase in the intensity of the attribute is observed for 3MH as the concentration is progressing. The same cannot be said for 3MHA; once more and more 3MHA is added to the matrix, the perception of ‘red berries’ follows a bell-shaped pattern inwhich amaximum intensity is reached, but decreases once the concentration keeps on increasing.

2d

2c

SUMMARY We discussed the results of Experiment 2 in which we evaluated the interaction 3MH x 4MMP and 3MHA x 4MMP in a single wine base. From the results, we saw the attributes generated through interaction, the relationship between the samples and how interaction affected the perception of particular attributes. For more information, contact Valeria Panzeri at valeria.panzeri@icloud.com or Astrid Buica at abuica@sun.ac.za.

into play and the intensity is hampered, resulting in the visual depression in the middle of the surface plot (figure 2d). TAKE-HOME MESSAGE This experiment demonstrated that, in the case of one thiol, the perception is often non-linear. Once a second thiol is added to the mixture, the effect is even more complex and cannot be predicted from the behaviour of single compounds. Even with a relative simple mixture of two compounds, we can see major synergistic and masking interaction effects and very seldom additive.

WINETECH TECHNICAL YEARBOOK 2020 90