Green recovery of phenolic-rich extracts from pineapple crowns using deep eutectic solvents: FTIR characterization and chemometric optimization

This study presents an integrated green analytical strategy combining deep eutectic solvent (DES) screening, Fourier transform infrared spectroscopy (FTIR), principal component analysis (PCA), and Box–Behnken response surface optimization for the valorization of pineapple crowns, an underexplored agro-industrial by-product. An ultrasound-assisted extraction (UAE) method was developed using DESs to obtain phenolic-rich extracts from pineapple (Ananas comosus) crowns. Five DES formulations were characterized by FTIR to evaluate their characteristic vibrational features, while extraction performance was assessed using total phenolic content (TPC) and antioxidant activity determined by the DPPH assay. Among the tested solvents, glycerol/urea (1:1, molar ratio) exhibited the highest extraction performance based on TPC and antioxidant activity measurements. PCA was used as a complementary tool to visualize the relationships among the DES formulations. Following preliminary temperature screening, 50 ◦C was selected for the optimization experiments. The extraction conditions were optimized using a Box–Behnken design coupled with response surface methodology (BBD–RSM), while desirability function analysis was applied to identify the optimum extraction conditions. The predicted optimum conditions were a sample mass of 1.09 g, an extraction time of 24.75 min, and a water content of 38.21%, yielding predicted responses of 34.66 mg GAE/g air-dried sample (ADS) for TPC and 12.30 mg Trolox equivalent antioxidant capacity (TEAC)/g-ADS for antioxidant activity. Experimental confirmation at the optimum showed deviations below 2% between predicted and observed responses, supporting the adequacy of the models. The quadratic models showed high goodness of fit (R2 = 0.9871 for TPC, and R2 = 0.9906 for antioxidant activity). Overall, the integration of DES-based UAE, FTIR characterization, PCA, and chemometric optimization provides a sustainable analytical approach for producing phenolic-rich extracts from pineapple crown biomass.