OPTIMIZATION OF PECTIN EXTRACTION FROM ARAÇÁ-BOI (EUGENIA STIPITATA) FIBROUS RESIDUE ASSISTED BY ULTRASOUND

Pectin is a biopolymer widely used in the food, pharmaceutical, and cosmetic industries. The peel of araçá-boi (Eugenia stipitata), a frequently discarded agro-industrial byproduct, offers a promising source of pectin. Ultrasound-assisted extraction (UAE) is an effective method for improving pectin recovery, reducing energy consumption, and shortening processing time. The objective of this study was to optimize UAE conditions for extracting pectin from araçá-boi peel, focusing on yield. Fruits collected in the city of Manaus (Amazonas, Brazil; 3°6′7″S, 60°1′30″W) were sanitized and pressed to obtain juice, leading to the production of a fibrous residue, which was dried at 60 °C and processed. Fibrous residue flour (FRA) was obtained by sieving (20 mesh). Soluble compounds were removed using 80% ethanol (1:3 w/v, 33 min, 70 °C), and the residue was dried at 40 °C, resulting in the alcohol-insoluble residue (AIR) used for extraction. Optimization was conducted using a Central Composite Design (CCD) employing three independent variables, which resulted in 18 experimental runs. The independent variables and their levels were: ultrasonic amplitude (30–90%), solid-to-liquid ratio (SLR, 1:76–1:21 w/v), and pH (1.5–3.5), with a fixed sonication time of 10 minutes. The response variable was pectin yield (%). The quadratic model fitted to the experimental data showed good predictive capability (R² = 0.8981, adjusted R² = 0.78347) and was statistically significant (F = 8.4613), confirming its adequacy. Significant quadratic effects were observed for amplitude (x₁², p = 0.005346) and SLR (x₂², p = 0.001497), indicating optimal operating ranges. Although pH (x₃) and the interaction terms (x₁x₂, x₁x₃, x₂x₃) were not statistically significant (p > 0.05), maximum yields (~6.99%) occurred with amplitudes between 60–70%, SLR around 1:33, and pH close to 2.5. Very high or low values of these parameters led to reduced efficiency due to effects like solvent saturation, limited diffusion, or pectin degradation. These findings demonstrate the importance of optimizing variable combinations to maximize UAE efficiency. This study confirms the feasibility of UAE for extracting pectin from araçá-boi residues, especially when amplitude and SLR are properly adjusted. The method presents a sustainable alternative for valorizing agro-industrial byproducts, in line with green chemistry principles. Further studies are recommended to explore pulsed ultrasonication modes, additional extraction parameters, and industrial-scale applications.