Response surface method – Molecular gastronomy (II)

Now we are ready to go forward with the results. The experimental results are presented below.

Table 1. Experimental results of sphere formation using the pisco mix.

In this opportunity, we will analyze some of the most important parameters to ensure the validity of the model obtained by applying the response surface methodology. The experimental results obtained using the response surface methodology are evaluated by applying ANOVA. The most influential factors or interactions are determined according to the p-value. A p-value less than 0.05 indicates that the factors are significant or influence the final response (sphere shape). Factors A, B, C, D and the interactions BC and BD were found to be significant. Likewise, the lack of fit is determined to be non-significant. The lack of fit of 7.61% indicates the probability that the lack of fit value is due to noise. Although it complies with a p-value over 0.05, it is recommended that the lack of fit value be greater than 10%.

Table 2. ANOVA for the response surface model.

The estimated coefficients represent the change that would occur in the response if these factors were removed and the other factors were kept constant. When the factors are orthogonal the variance inflation value (VIF) is 1. As a rule of thumb, the VIF is expected to be less than 10.

Table 3. Variance inflation as a function of the coded terms.

Table 4 presents the equation obtained represented as a function of the coded factors. Therefrom we can make predictions about the response for a given level on each factor. High-level values are coded as +1 and low levels as -1 by default. In this way, we can compare the relative impact of the factors on the response by comparing their coefficients.

In general, it can be observed that the Pisco concentration (Factor A) and the interaction between CaCl2 concentration and alginate concentration (BC) have an unfavorable influence on sphere formation. On the other hand, the alginate concentration is the factor that favors the formation of the spheres.

Table 4. Model in terms of the codified factors.

Figure 1 shows the spheres of pisco macerate obtained.

Figure 1. Strawberry (left) and passion fruit (right) pisco mix spheres.

Figure 2 shows the interaction between CaCl2 and alginate concentration in the formation of the spheres of the pisco mix. It can be observed pisco concentration up to 30% of the spheres formed with the strawberry mix have a better appearance compared to those of the passion fruit mix. In both cases, higher alginate and low CaCl2 concentration favor the formation of the spheres.

Figure 2. Contour plots of the influence of CaCl2 and alginate on sphere formation with strawberry (left) and passion fruit (right) pisco macerate.

Figure 3 shows how pisco sphere formation is favored with increase alginate concentration for both strawberry and passion fruit macerates. At the same time, it is observed that the CaCl2 concentration does not have a very influential effect compared to the alginate concentration on the formation of the pisco macerate spheres. These three-dimensional plots are projected onto the alginate vs. CaCl plane to obtain the contour plots seen previously (Figure 2).

Figure 3. Three-dimensional representation of the spheres of strawberry (upper) and passion fruit (lower) macerate at 30%.

The decrease in alcohol concentration in the passion fruit macerate spheres favors their formation (Figure 4). Remember that the pisco is mixed with tonic water in different proportions.

Figure 4. Three-dimensional representation of passion fruit mix spheres with 10% alcohol.

In Figure 5 it can be observed that the increase of alcohol concentration in the macerate spheres does not favor their formation.

It can be determined that the alginate concentration, the pisco flavor, and the alcohol concentration have a significant influence on the formation of the spheres.

Figure 5. Three-dimensional representation of passion fruit macerate spheres with 50% alcohol.

We learned a little more about the response surface methodology. Now you can enjoy your pisco mix in this fun presentation.

Design-Expert 12 (StatEase, Minneapolis - USA) software was used in the creation and analysis of this optimal design with the surface response method.

Figure 6. Strawberry (left) and passion fruit (right) mix in the form of spheres ready to enjoy.

You can try these delicious pisco mixes by looking at the following link Kusikuy on instagram.

Figure 7. Strawberry pisco with eucalyptus (left) and passion fruit with ginger (right) macerate from the brand kusiky (@kusikuy_macerados).

©Daniel Obregón, 2021