3.4.1. Color

Color parameters (L, a\*, and b\*) were measured through the bottom of the same transparent trays during the study (Table 3).

L values were higher in white prickly pear trays than orange ones. The WE treatment led to a higher brightness (L) than the WH treatment; in the orange pears, these differences were only appreciated from day 6 in the OE180P sample. The orange prickly pears had higher a\* values than the white ones, and they behaved differently during shelf life. However, the a\* value increased with storage time in white prickly pears but decreased in orange pears, with only OE90P showing significantly different values. The type of peeling influenced the a\* values shown by white prickly pears more than those shown by orange ones. Ultimately, WH presented a\* values higher than WE during shelf life (Table A1, Appendix A). The b\* parameter showed different trends depending on the studied prickly pear variety; WE showed higher values (*p* < 0.05) than those peeled manually (WH). In the orange variety from the first storage day, the highest and lowest b\* values were detected in OE180P and OH90P, respectively. In addition, this parameter seemed to considerably fluctuate in the white variety during storage time, especially in WE180P, while remaining more or less constant in the orange ones, especially in OE180P (Table A1, Appendix A). The tonality (H◦) decreased with storage time in the white prickly pears and remained more or less constant in the orange ones. In general, WE showed higher H◦ values than WH, and

its trend in orange pears was similar to that described for the b\* parameter. The orange variety showed lower H◦ values than the white variety. The type of film had little influence on the L, a\*, b\*, and H parameters. Electrically peeled white prickly pears showed higher chromaticity (C\*) values than those peeled by hand at each storage time independently of the film used; this fact was not observed in the orange variety. Allegra et al. [39] found reported unremarkable changes in flesh color occurring during the summer storage or late, freshly cut prickly pears that were harvested either at commercial harvest time or when fully ripe.


**Table 3.** Color parameters of white and orange minimally processed prickly pears that were manually or electrically peeled and packed in two films of different permeability during cold storage at 7 ◦C.

Hand-peeled (H) and electrically peeled (E) white (W) and orange (O) prickly pears packaged in 90PPlus (90P) and 180PPlus (180P) film. Different letters in a row indicate that there were significant differences between storage days (*p* < 0.05), and different numbers in a column indicate that there were significant differences between samples (*p* < 0.05).

**Figure 2.** Taster evaluation of the color, smell, taste, and overall appearance of hand-peeled (H) and electrically peeled (E) white (W) and orange (O) prickly pears packaged in 90PPlus (90P) and 180PPlus (180P) film.

**Figure 3.** (**a**) CO2 and O2 concentration (%) evolutions inside white prickly pear trays; (**b**) CO2 and O2 concentration (%) evolutions inside orange prickly pear trays. Hand-peeled (H) and electrically peeled (E) white (W) and orange (O) prickly pears were packaged in 90PPlus (90P) and 180PPlus (180P) film.

In general, loss of color (ΔE) (Table 3) was only observed in electrically peeled prickly pears packed with 180PPlus film, though this parameter was not affected by storage time in the other types of prickly pears, even showing improvement in the case of WH90P. Allegra et al. [39] also reported losses of color, especially after 7 days of storage, as did Ochoa-Velasco and Guerrero-Beltrán [40]. Film type did not influence color loss, with the exception of the OE packed with 90P film that presented higher losses than those packed in 180PPlus film. The whiteness index (WI) significantly increased with the storage time in all types of studied orange prickly pears, though it did not change over time in the white

ones, except in WH180P in which it decreased. Likewise, the WI was much higher in white prickly pears than in the orange ones. The types of peeling and film did not significantly affect this parameter.

#### 3.4.2. Hardness and Texture

The hardness (Table A1, Appendix A) did not significantly change over the 8 days of cold storage in the studied varieties, except when the white ones were electrically peeled and packed in either of the two films. The hardness of the electrically peeled white and orange prickly pears was higher (50.8 and 42.9 ◦Durofel for white and orange varieties, respectively) than that of the manually peeled pears (32.1 and 31.3 ◦Durofel for white and orange varieties, respectively) for all storage times and both types of film. Hardness presented significantly different values during the entire shelf life of the white prickly pears, but the hardness values stopped showing differences by day 3 for the orange prickly pears. The influence of the type of film used was negligible, especially in the orange prickly pears; it was only detected that WH180P showed higher (*p* < 0.05) hardness values than WH90P from day 1 to day 6 of packaging. Another interesting parameter was texture, which was evaluated with a Kramer cell that simulated mastication (Table A1, Appendix A). We found that texture significantly increased during the 8 days of storage, except in WH90P, OE180P, and OE90P, for which it decreased (*p* < 0.05). White prickly pears showed higher texture values than the orange ones during shelf life (10.6 and 6.1 N s/g f.w., respectively). In addition, the texture values were significantly higher when the white prickly pears were peeled by hand than with the electric peeler (11.7 and 9.5 N s/g f.w., respectively). In the orange variety, the electrically peeled fruits presented significantly higher values than the manually peeled ones at the beginning of cold storage. The type of film used in packaging did not influence this parameter.

#### 3.4.3. Dry Matter, pH, and Acidity

At the beginning of storage, the dry matter content (data not shown) was higher in the white prickly pears than in the orange ones (19.8% and 17.5%, respectively), and it was higher in those white fruits peeled by hand than with the electric peeler (21.1% and 18.5%, respectively). Thus, WH were the prickly pears with the highest dry matter values (≥20.5%), and the OE showed the lowest values (<16.5%). Likewise, the dry matter contents of both varieties, regardless of the type of film and peeling, remained almost constant throughout cold storage, which was similar to the results reported by Piga et al. [12] for the "Gialla" variety. The hand-peeled prickly pears showed higher pH values and lower acidity values than the electrically peeled pears (data not shown). It was observed that the pH significantly decreased after 8 days of storage in WH180P, OH180P, and OE180P, and the acidity significantly increased in WH180P, OH90P, and OE180P. In the other treatments, both pH and acidity remained constant over time. Accordingly, the lowest pH value was detected in OE180P at 8 days of storage (pH = 5.39), and pH values lower than 6 were also observed in OE90P. The film used in packaging had little impact on the values of these two parameters in the studied varieties. Piga et al. [12] analyzed prickly pears of the "Gialla" variety and reported similar results (decreases in pH during storage) when fruits were manually peeled and stored at 4◦ C for 9 days. Ochoa-Velasco and Guerrero-Beltrán [40] detected decreases in pH with storage time (16 days at 4◦ C) in white prickly pears of the *O. albicarpa* species. However, Palma et al. [38] reported that pH and acidity significantly decreased with storage time (at 4 ◦C/10 days) in the orange "Gialla" variety, though they remained constant in the white "Bianca" variety.
