## 3 Results and Discussion  
### Antioxidant Capacity  
After applying the FCR, the TPC content in the pineapple core was on average slightly higher than in the peel as shown in Table 2. Core values ranged from 66 to 22 mg GAE 100 g\({}^{-1}\), presenting all the samples' significantly different content, meanwhile, in the peel samples the values were comprised between 41 and 15 mg GAE 100 g\({}^{-1}\). The peel S2 sample was the one with the higher TPC. From the data obtained some variability among samples was found. As was mentioned in the introduction section, the TPC is dependent on the extractant employed in the ripeness stage and the part of the fruit; for that reason it is common to find differences among samples from different origins. Nonetheless, the variability indicated that the values obtained are in the same range of concentration as others found in the literature using similar extractants. [PERSON] et al. [34], for example, found the content of about 75 mg GAE 100 g\({}^{-1}\) fresh weight in the fruit which is only a little bit higher than the values obtained in the present study in the core and peel of pineapple. In another study, the effect of the extractant was studied over the TPC in three pineapple cultivars. The methanolic extracts evaluated, which were the most similar to the one employed in the present study, showed TPC ranging from 30 to 54 mg GAE 100 g\({}^{-1}\) of fresh weight [35] and similar variability values among samples to the ones encountered here.  
Regarding the TPC in the pineapple wastes, in a recent study in which different proportions of ethanol in the extractant were assayed, the highest content resulted to be 12.71 mg GAE g\({}^{-1}\) dry basis of pineapple crown extracts [13]. The peel and core extracts showed slightly lower values, 10.7 and 4.8 mg GAE g\({}^{-1}\) dry basis, respectively, from 50% ethanol extracts [13]. Considering that the average water content for the core pineapple could be 89.4% [34], the 4.8 mg GAE g\({}^{-1}\) dry basis found in the core corresponds approximately to 53 mg GAE 100 g\({}^{-1}\) fresh weight. This value is very close to the one observed in core S1 and core S2 and slightly higher than in core S3.  
Furthermore, other antioxidant assays based on electron transference were applied to compare the antioxidant behavior of the pineapple extracts under a different mechanism of reaction and pH. Thus, the FRAP assay was carried out under acidic pH, the ABTS and DPPH under neutral, and the TPC under basic pH. Independently on the assays employed, some significant differences were observed among the samples of the same type, which corroborates the influence in these parameter factors such as the ripening stage, the cultivar, and growing conditions, among other variables. A comparison with literature is not exactly possible as the values obtained depend on the extractant, the state of the sample, and the extraction conditions. Anyhow, it seems that the values obtained by [PERSON] et al., were in the same range of concentration as the ones obtained here [34]. In that study, different tropical fruits were compared and for the pineapple, they found values near 170 umol TE 100 g\({}^{-1}\) in the ABTS and DPPH assay. Nevertheless, the value found by [PERSON] et al. was nearly double the values encountered in the present study. For the three assays, the core and peel antioxidant content were similar; only the peel S2 sample seems to show a higher content compared to the rest. Other data found in the literature are expressed per g of dry extract or sample, and for that reason is not possible to compare the results with those works [9; 22; 35]. From the data obtained on the core and peel pineapple antioxidants content, it can be remarked that those waste parts have similar antioxidant content as the edible pineapple pulp and that the content is very dependent on the ripeness stage.