VALORIZATION OF PINEAPPLE PEEL AS A SOURCE OF PHENOLIC COMPOUNDS AND ANTIOXIDANTS

The pineapple (Ananas comosus L. Merr.) is one of the world's major tropical fruits. Industrial processing generates large quantities of waste, primarily peels, which can account for 40% to 60% of the fruit's mass and represent an important source of bioactive compounds. Therefore, this study aims to determine the total phenolic content and evaluate the antioxidant capacity of pineapple peel flour extract.The sample was extracted using 70% ethanol at a 1:40 (m/v) ratio and agitated at 200 rpm for 90 minutes at 25°C. The samples were centrifuged at 8,000 rpm for 10 minutes at 10°C. The supernatant was filtered through qualitative filter paper, placed in amber vials, and stored at -18°C.Total phenolic content was determined using the Folin-Ciocalteu method, employing a 1:5 (v/v) extract dilution. Briefly, 0.5 mL of extract, 2.5 mL of Folin-Ciocalteu reagent (10%), and 2 mL of 7.5% Na2CO3 were mixed and incubated in a water bath at 50°C for 6 minutes. Absorbance was measured at 750 nm using a UV/Vis spectrophotometer.Antioxidant activity via DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging was quantified using 100 μL of diluted sample (1:5, v/v), 4.0 mL of ethyl alcohol, and 1.0 mL of 250 μM ethanolic DPPH• solution. After 30 minutes, absorbance was measured at 517 nm. For ABTS+• (2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging, 30 μL of diluted sample (1:5, v/v) was added to 3.0 mL of ABTS+• solution. After homogenization, the tubes were kept in the dark at room temperature for 6 minutes, and absorbance was measured at 734 nm.Reducing power was evaluated using the FRAP (Ferric Reducing Antioxidant Power) method. A 45 μL aliquot of diluted sample (1:1, v/v) was mixed with 315 μL of distilled water and 2.7 mL of FRAP reagent. After homogenization, samples were incubated at 37°C for 30 minutes, and absorbance was measured at 595 nm.The total phenolic content was 6.319 ± 0.130 mg GAE/g. Antioxidant activity values were 27.428 ± 2.095 µmol TE/g for DPPH, 32.767 ± 3.886 µmol TE/g for ABTS, and 100.155 ± 3.584 µmol TE/g for FRAP.The higher FRAP response suggests greater reducing capacity toward ferric ions than radical-scavenging activity under the evaluated conditions. This difference reflects the complementary nature of these assays, which rely on distinct reaction mechanisms. Previous studies have reported phenolic compounds and antioxidant activity in pineapple peel, emphasizing the effects of cultivar, processing, drying, solvent, and extraction conditions on bioactive compound recovery and activity.These results demonstrate that pineapple peel flour contains extractable compounds with antioxidant properties and support its potential as a raw material for value-added food ingredients. Its utilization may contribute to agro-industrial by-product valorization and more sustainable food production.