## 3 Results and Discussion  
### Effect of Biosurfactant Extract on the Grape Morphology  
The overall objective of the work was to visualize micro-morphological changes in the grape peel during storage when treated with a biosurfactant solution (coated grapes) or untreated (non-coated grapes). Therefore, grapes were coated with a biosurfactant extracted from CSL in order to evaluate the effect of this bioactive extract on the peel surface of the grapes. This biosurfactant extract possesses a CMC of 306.5 mg/L, and it is able to reduce the surface tension of water to 43.8 mN/m [3]. The grapes were coated with a solution of this biosurfactant extract at a concentration of 1 g/L in order to achieve a bactericide concentration determined in previous work [2]. Figure 2 shows the area, perimeter, major axis length, and minor axis length of coated grapes and non-coated grapes at different storage times. It was observed that coated grapes underwent fewer alterations in these parameters than non-coated grapes. For instance, the area of the non-coated grapes decreased 12.3% after 11 days of storage, whereas the coated grapes decreased 10.0%, although the major difference was noticed in the major axis and minor axis length. In the coated grapes, the major and minor axis decreased 3.8% and 5.0%, respectively, whereas the non-coated grapes decreased 6.3% and 7.6%, respectively. It can be speculated that the biosurfactant extract prevents or reduces water loss in grapes, thus maintaining the shape of the grapes for a greater period of time than non-coated grapes. Additionally, a morphological study that includes the evaluation of grape roughness was carried out. Tables 1 and 2 include the roughness parameters obtained for the two scenarios, taking into consideration roughness and shape or only roughness, respectively, following the ISO 25178-1 [23]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{6}{c}{**NON-COATED GRAPES (FINE STRUCTURE + SHAPE)**} \\ \hline
**Parameter** & **Units** & **1 Day** & **3 Days** & **5 Days** & **9 Days** & **11 Days** \\ \hline  
** & & 0.43 \(\pm\) 0.27 & 0.30 \(\pm\) 0.14 & 0.22 \(\pm\) 0.06 & 0.87 \(\pm\) 0.32 & 1.29 \(\pm\) 0.24 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Roughness parameters for non-coated and coated grapes without eliminating the shape effect. Figure 2: Changes produced in the size of grapes at different storage times. In one case, shape and roughness were taken into consideration together to establish these values (see Table 1), and in the other case, a filter was applied to the images in order to eliminate the effect of shape on the roughness values (see Table 2). When shape and roughness are considered together, the values obtained are strongly affected by the cylindrical shape of the grape, as the height (z) values of the shape are much higher than those of the roughness. Therefore, for a more exhaustive study of roughness, the effect of the shape was eliminated (Table 2) and compared with those values where the shape was considered (Table 1). The most representative parameters for measuring the roughness are the Sa and Sq values, which evaluate the changes in the height differences between points measuring the deformation of the surface, observing that these values from day 3 were always lower in coated grapes compared with non-coated grapes. Roughness can be interpreted based on observing the changes in the fine texture and shape (see Table 1) or just based on fine texture (see Table 2). In both sceneries, coated grapes resist showing changes in roughness for many days, while the untreated grapes quickly showed alterations in the structure of the peel. The roughness changes in the treated grape begin to be noticeable after 9 days when fine texture and shape are considered, while in the non-coated grapes, these significant changes were observed from day 3, which is an indication that deterioration was much faster in untreated grapes than in treated ones.