3.4.4. Sugars

In general, the TSS content was higher in the white prickly pears than in the orange ones (Table 4). However, Palma et al. [38] did not observe that the prickly pears of the "Bianca" variety were sweeter than those of the "Gialla" variety. The prickly pears with the highest and lowest TSS were WH and OE, respectively, which coincided with the results


**Table 4.** Total soluble solids, fructose, glucose, and sucrose contents in white and orange minimally processed prickly pears peeled by hand or with an electric peeler 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).

#### 3.4.5. Bioactive Compound and Antioxidant Capacity Analyses

The ascorbic acid content considerably varied depending on the variety, storage time, and type of peeling (Table 5), but the type of film showed little influence. A decrease in ascorbic acid during storage was observed, and it was more pronounced in the electrically peeled pears. Palma et al. [38] reported a decrease in ascorbic acid content during the storage of the "Bianca" and "Gialla" varieties. In contrast, Piga et al. [12] did not describe any significant differences in the content of this vitamin during the storage of the minimally processed "Gialla" variety. However, it should be noted that after 8 days of storage at 7 ◦C in this study, the ascorbic acid content ranged between 15 and 21 mg/100 g of fresh weight, with losses relative to the initial time ranging between 8% and 38%. Significant differences were also detected between the white prickly pear treatments for each day of storage, and we obtained different results for the orange variety. WE showed higher values (*p* < 0.05) of ascorbic acid for all storage days than WH, but those differences in the orange ones were not significant (*p* > 0.05) (except on day 3, in which OH showed higher values than OE).

**Table 5.** Ascorbic acid, total phenolics, and antioxidant capacity (DPPH) in white and orange minimally processed prickly pears peeled by hand or with an electric peeler 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).

Total phenolic content increased with storage time (Table 5). Ochoa-Velasco and Guerrero-Beltrán [40] found that the phenolic content in white prickly pears slightly decreased during storage but significantly increased in red prickly pears after 4 days of storage. In contrast, Palma et al. [38] reported decreases in the contents of these compounds over storage time in the "Bianca" and "Gialla" varieties and Piga et al. [12] described a decrease after 3 days of storage at 4 ◦C in the "Gialla" variety. In our study, the white and orange

varieties suffered more noticeable increases from days 3 and 1 of storage, respectively. It was also observed that the peeling method influenced the antioxidant compound contents; the electrically peeled pears showed higher values than the hand-peeled pears. Significant differences were observed in OE depending on the type of film, with the exception of days 0 and 3. In contrast to total phenolic content, as storage time progresses, a decrease in antioxidant capacity (DPPH) was observed for both varieties. These results were similar to those obtained by Palma et al. [38] in the "Bianca" variety but not in the "Gialla" variety, as well as those of Piga et al. [12]. No significant differences were detected in antioxidant capacity (DPPH) depending on the type of film used or the type of peeling performed, except for WH fruits that presented higher values than WE at the moment of processing.

## **4. Conclusions**

In this study, minimally processed white and orange prickly pears maintained suitable microbial and nutritional quality after 8 days of storage at 7 ◦C. Throughout storage, the counts of microorganisms increased regardless of the variety, peeling method, or microperforated film used. However, the counts of aerobic mesophiles bacteria remained below the limits established by the Spanish legislation (<7 log(CFU/g f.w.) until day 8. Similarly, the counts of psychrophiles, molds, and yeasts did not exceed values of 6 log(CFU/g f.w.).

Electrically peeled prickly pears presented interesting characteristics from a technological and nutritional point of view. Moreover, the contents of bioactive compounds such as ascorbic acid and total phenolic compounds were higher in the electrically peeled fruits.

Fresh-cut orange prickly pears were well evaluated independently of the peeling method and the micro-perforated film used from the beginning to the end of the experiment. White prickly pears were initially evaluated less well when peeled with the electric peeler than with the knife because the electrically peeled pears presented part of the thick pericarp characteristic of this variety.

We recommend using the 180PPlus film and adjusting the electric peeling method depending on the thickness of the prickly pear pericarp to prevent consumers from perceiving any unpleasant sensation, as occurred with the white prickly pears used in this study.

Electrically peeled minimally processed prickly pears could be a value-added healthy alternative because of their high nutritional quality, thus facilitating their consumption. The by-products generated in the agro-industries can be used for animal feeding or as sources of antioxidants, fiber, natural colorants, mucilage, etc.

**Author Contributions:** Conceptualization, M.G.L. and G.L.D.-D.; methodology, M.G.L., G.L.D.-D., E.M.R.-R. and E.D.; software, E.M.R.-R. and G.L.D.-D.; validation, E.M.R.-R., G.L.D.-D. and M.G.L.; formal analysis, G.L.D.-D. and E.M.R.-R.; investigation, G.L.D.-D., M.G.L., E.M.R.-R. and E.D.; resources, M.G.L.; data curation, G.L.D.-D. and E.M.R.-R.; writing—original draft preparation, G.L.D.-D.; writing—review and editing, M.G.L., E.M.R.-R. and E.D.; visualization, G.L.D.-D., M.G.L., E.M.R.-R. and E.D.; supervision, M.G.L. and E.M.R.-R.; project administration, M.G.L.; funding acquisition, M.G.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by "Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA)", gran<sup>t</sup> number RTA 2015-00044-C02 "Estudio integral de aprovechamiento de Opuntia (Tuna o Higo Chumbo) para la obtención de derivados e ingredientes funcionales mediante la aplicación de tecnologías innovadoras".

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the sensorial evaluation.

**Data Availability Statement:** Data will be made available on reasonable request.

**Acknowledgments:** The authors would like to acknowledge the support and collaboration given by the orchard farmers.

**Conflicts of Interest:** The authors declare no conflict of interest.
