## 3 Results and Discussion
### Content and Retention Efficiency of Bioactive Compounds and Antioxidant Capacity in Microcapsules
SD: spray drying; SFB: sprout-fluid bed drying; AC: antioxidant capacity. Different capital letters indicate significant difference in the same sample (extract, microcapsules and dehydrated Mexican plum powder), and lower-case letters indicate significant difference between group (initial content, recovery index and bioaccessibility index). acid was more stable in acidic conditions than in alkaline [15]. During the gastric stage, the hydrochloric acid lowered the pH to 2.5, which might help to increase the ascorbic acid stability. The loss of ascorbic acid during intestinal digestion could be due to pH (7) changes and the presence of oxygen after the enzymatic digestion process contributing to the ascorbic acid degradation. SFB microcapsules showed the highest BI for DHA (96.19%) and total vitamin C (79.70%). Regarding AA, the highest RI was obtained for the Mexican plum powder (83.60%), but the highest BI was obtained for the extract. No significant difference was observed for the AA in the BI between the microcapsules by SD and SFB. For both SD and SFB microcapsules, AA content significantly decreased at the end of the gastric and intestinal phases; however, the DHA and total vitamin C (DHA + AA) contents increased in the intestinal phase (BI). This could be explained by (enzymatic and no enzymatic) AA oxidation into DHA during simulated digestion [43]. These results agree with [PERSON] et al. [44], who reported that AA oxidization can occur after a long storage or after a heat or mechanic treatment, besides intestinal conditions, such as:neutral pH, oxygen, temperature, enzymatic activity (ascorbate-oxidase) and the presence of minerals as copper and iron. As is shown in Figure 4a-f, for Mexican plum extract without any protection and dehydrated plum powder, BI is always lower than RI (PC, AA, DHA, total vitamin C, ABTS, DPPH), but for microcapsules, this is not the case. The role of the microcapsules is to protect bioactive compounds from the gastric environment and release them in the intestine for possible absorption. As Figure 4 shows, this is the case for phenolic compounds but not for AA that is very unstable under digestion conditions. Based on data shown in Figure 4b, both SD and SFB microcapsules did not protect AA, showing a reduction in AA of about 30% for SD and 27% for SFB microcapsules. If we assume that AA was oxidized to DHA due to pH and enzymic action on the molecule, then we would expect an increase of the same magnitude on DHA. Figure 4c shows that DHA increased from about 50% for SD and 55% for SFB microcapsules in the gastric digestion (RI) to about 80% (for SD) and about 90% for SFB in the intestinal digestion (BI), which is an increase of about the same order that was expected due to the loss of AA. The microcapsules obtained by both drying methods proved to protect phenolic compounds, dehydroascorbic acid and total vitamin C from degradation during in vitro digestion in the intestinal phase, where the highest percentages of bioaccessibility were obtained, compared to the extract without microencapsulation and the powder dehydrated Mexican plum. The RI and BI for AC by ABTS and DPPH are shown in Figure 4e,f, respectively. The lowest RI and BI for the antioxidant capacity by ABTS and DPPH were observed in the extract. These results shown that the bioactive compounds in the extract, which have an antioxidant effect, are exposed and are more susceptible to degradation during the digestion process. The Mexican plum powder obtained higher RI for ABTS and DPPH than the extract and microcapsules, while the highest BI was obtained by SD microcapsules for ABTS and by SBD microcapsules for DPPH. These results show that the microencapsulation of Mexican plum extract helps to avoid bioactive compounds' degradation that contributes to antioxidant capacity. It should be noted that the Mexican plum powder displayed a similar DPPH BI that of the SD microcapsules. These results can be explained due to pH variations during digestion.