The majority of the published studies define the firmness as the resistance to a deformation of the skin measured either with a shoremeter or densimeter, equipped with a 5- [
10,
12,
14,
38,
39] or 2-mm probe [
55], expressed in Newton/cm
2, or with a momentum transfer generator (MTG), that reports the olive firmness as MTG units [
28]. From the first studies on, it was demonstrated that the maintenance of flesh firmness depended on storage temperature [
10]. At 5 °C, the initial values are maintained, while at ambient temperature they fell to almost 50% after 30 days of storage. At 8 °C, a moderate decrease was observed up to 60 days [
17]. The fruit firmness of black-ripe olives declined by 24.4–45.9% in air and 34.2–38.0% in 2 kPa O
2 after 4 weeks of storage [
28]. These observations were contrary to results on mature green olives which firmness was better when stored under 5 or 2 kPa O
2 [
14]. However, ‘Gordal’ olives stored under 1 kPa O
2 did show a decrease in firmness [
10]. The firmness of black-ripe olives at 20 °C decreased by 44% within the first 2 weeks, which was much lower than any of the other examined. Variations among cultivars were observed [
26,
38]. A clear difference was registered between the ‘Mission’ and ‘Sevillano’ varieties, which maintained their firmness up to 8 weeks, and the ‘Acolano’ and ‘Manzanillo’ cultivars, which, respectively, lost 9 and 29% of their firmness at 4 weeks and 16 and 53% at 8 weeks [
26]. Significant differences occurred between ‘Picual’, showing a significant reduction of the firmness after 1 week, and the ‘Manzanilla’ and ‘Verdial’ varieties, only after 4 and 6 weeks, respectively [
38]. Hand-harvested olives softened slower as compared to mechanic harvest. However, it was only after 10 days of storage at 5 °C that a significant difference was observed. A difference that was contributed to the internal partial breakage of the cellulose walls of the cells of the mesocarp during mechanical harvesting [
39]. A similar observation was made in a recent research [
45], in which the use of nets was the damaging factor.