## 3 Results and Discussion
### Total Phenolic Content and Antioxidant Activity
#### 3.1.2 Pineapple Core  
The TPC (Figure 3) showed a significant (\(p<0.05\)) increase (17%) in the sample wounded with heat treatment at 40 \({}^{\circ}\)C and storage time of 24 h (95.34 \(\pm\) 0.82 mg CAE.g\({}^{-1}\) dry matter), compared to the raw material (81.53 \(\pm\) 0.81 mg CAE.g\({}^{-1}\) dry matter). With the longest storage time, the TPC decreased, with a reduction of 7% for storage time 24 h (76.02 \(\pm\) 0.60 mg CAE.g\({}^{-1}\) dry matter) and 27% for storage time 48 h (59.59 \(\pm\) 0.69 mg CAE.g\({}^{-1}\) dry matter). Wounding (63.93 \(\pm\) 0.59 mg CAE.g\({}^{-1}\) dry matter) reduced significantly (\(p<0.05\)) the TPC in 22% compared to the raw material (81.53 \(\pm\) 0.81 mg CAE.g\({}^{-1}\) dry matter), although the reduction is only of 3% in the case of wounded samples with a storage time of 48 h (78.92 \(\pm\) 0.61 mg CAE.g\({}^{-1}\) dry matter). The abiotic stress (Figure 4) caused by the wound along with the storage time promoted a significant increase in antioxidant activity (_p_ < 0.05). The samples with wound and storage time 24 h showed an increase in antioxidant activity of 12%, 16%, and 11% by the DPPH (41.04 \(\pm\) 0.71 umol Trolox g\({}^{-1}\) dry matter), FRAP (33.06 \(\pm\) 0.77 umol Trolox g\({}^{-1}\) dry matter) and ABTS (40.55 \(\pm\) 0.58 umol Trolox g\({}^{-1}\) dry matter) methods, respectively, compared to the raw material (DPPH: 36.62 \(\pm\) 0.91 umol Trolox g\({}^{-1}\) dry matter; FRAP: 28.55 \(\pm\) 0.63 umol Trolox g\({}^{-1}\) dry matter; ABTS: 36.62 \(\pm\) 0.80 umol Trolox g\({}^{-1}\) dry matter). The samples with wound and storage time 48 h showed a significant increase of 9% by the DPPH (39.76 \(\pm\) 0.86 umol Trolox g\({}^{-1}\) dry matter) method, 17% by the FRAP (33.33 \(\pm\) 0.62 umol Trolox g\({}^{-1}\) dry matter) method and 11% by the ABTS (40.77 \(\pm\) 0.63 umol Trolox g\({}^{-1}\) dry matter) method, compared to the raw material, respectively. The samples wound with storage time 24 h and 48 h showed no significant differences in antioxidant activity by any of the methods studied (DPPH, FRAP, and ABTS). The maximum antioxidant activity obtained by the FRAP method was observed for the wounded sample, with heat treatment at 40 \({}^{\circ}\)C and storage time 24 h (34.90 \(\pm\) 0.70 umol Trolox g\({}^{-1}\) dry matter), which registered an increase of 22% (_p_ < 0.05), compared to the raw material (28.55 \(\pm\) 0.63 umol Trolox g\({}^{-1}\) dry matter). As observed in TPC, the increase in storage time maintained or reduced the antioxidant activity (Figure 4). The storage time of 24 h maintained the antioxidant activity as measured by the FRAP (28.77 \(\pm\) 0.77 umol Trolox g\({}^{-1}\) dry matter) method and reduced the antioxidant activity by 5% when evaluated by DPPH (35.00 \(\pm\) 0.96 umol Trolox g\({}^{-1}\) dry matter) and ABTS (34.90 \(\pm\) 0.67 umol Trolox g\({}^{-1}\) dry matter), compared to the raw material, respectively. In the case of storage time 48 h, the antioxidant activity decreased significantly (_p_ < 0.05) 25%, 51%, and 23% by the DPPH (27.57 \(\pm\) 0.68 umol Trolox g\({}^{-1}\) dry matter), FRAP (14.12 \(\pm\) 0.75 umol Trolox g\({}^{-1}\) dry matter) and ABTS (28.15 \(\pm\) 0.66 umol Trolox g\({}^{-1}\) dry matter) methods, respectively, compared to the raw material (DPPH: 36.62 \(\pm\) 0.91 umol Trolox g\({}^{-1}\) dry matter; FRAP: 28.55 \(\pm\) 0.63 umol Trolox g\({}^{-1}\) dry matter; ABTS: 36.62 \(\pm\) 0.80 umol Trolox g\({}^{-1}\) dry matter). Figure 3: Effect of abiotic stresses, heat treatment and wounding, on total phenolic content of pineapple core. Error bars stand for \(\pm\) standard deviation (_n_ = 9). Different letters express significant differences between samples. Figure 4: Effect of abiotic stresses, heat treatment and wounding, on antioxidant activity of pineapple core: (**a**) DPPH (2,2-diphenyl-l1-picrylhydrazyl); (**b**) FRAP (Ferric Reducing Antioxidant Power); and (**c**) ABTS (2,2’-azino-bis (3-ethylbenzothazoline-6-sulphonic acid)). Error bars stand for \(\pm\) standard deviation (\(n=9\)).