*2.4. Cracking Index, Soluble Cuticular Wax Content, and Texture Parameters*

The fruit cuticle is a hydrophobic and semi-permeable membrane consisting of two major lipid types: cutin and cuticular waxes [22]. Cuticular waxes play an important role in the water permeability of sweet cherries [23].

The correlation between the CI and the cuticular wax content is presented in Figure 4A. Cv. Early Bigi presented lower CI, but significantly higher wax content than cv. Lapins (*p* = 0.000). This means that these two parameters were negatively correlated (R<sup>2</sup> = 0.8389, *p* = 0.012). In general, the lower the wax content, the greater the water intake for the fruit, and consequently, the higher the cracking index. Indeed, according to [24], cultivars more tolerant to cracking have higher wax contents.

**Figure 4.** Correlations between (**A**) the cracking index (%) and the wax content (µg g−<sup>1</sup> ), (**B**) the cracking index (%) and the flesh firmness (N mm−<sup>1</sup> ), and (**C**) the cracking index (%) and the epidermis rupture force (N) of two sweet cherry cultivars: Early Bigi and Lapins.

Fruit firmness (FF) is an important quality attribute in sweet cherries, which is associated with a greater resistance to decay and mechanical damage, and consequently, to the increase of storage life [25]. In the present work, according to Figure 4B, the CI is positively correlated with the FF (R<sup>2</sup> = 0.7755, *p* = 0.021), being that cv. Lapins presented the highest values for both parameters. Indeed, cv. Lapins presented a significantly higher FF than cv. Early Bigi (*p* = 0.000). According to [26], sweet cherries with higher flesh firmness can have consequently fewer physiological disorders during handling, storage, and shipping, but according to [21], these firmer fruits are simultaneously more affected by cracking. In fact, it is usually assumed that cultivars with firm-fleshed fruits have more tendency to cracks, but the literature concerning this correlation is still very unclear [19]. It is likely that the epidermis elasticity is smaller in the hardest fruits.

In a previous work developed by [27,28], cv. Lapins presented an average fruit firmness of 2.65 N at harvest, which was lower than the results obtained in the present work for both cultivars (3.75 N for Lapins and 3.74 N for Early Bigi), perhaps due to the pre-harvest applied treatments and/or the different edaphoclimatic conditions.

No correlation was observed between the CI and the epidermis rupture force (ERF) (R<sup>2</sup> = 0.0099, *p* = 0.870) (Figure 4C). Furthermore, no significant differences were observed in ERF between cultivars (*p* = 0.963).
