OPTIMISATION OF ANTIOXIDANT ULTRASOUND ASSISTED EXTRACTION FROM PINEAPPLE PEEL AND COCOA POD MIXTURE USING RESPONSE SURFACE METHODOLOGY

Abstract

This study aimed to optimise the ultrasonic-assisted extraction (UAE) of antioxidants from a pineapple peel and cocoa pod mixture using Response Surface Methodology (RSM). Ethanol concentration and sample ratio showed the greatest influence on antioxidant extraction. Subsequently, extraction time, temperature, and sample ratio were optimised using a Box–Behnken design. The optimum extraction conditions were 20 min extraction time, 70 ℃ extraction temperature, and 90% mixture proportion. Under these conditions, the extract achieved the highest TPC (42.23 ± 0.30 mg GAE/g DW), TFC (16.80 ± 0.20 mg QUE/g DW), FRAP (4.08 ± 0.10 mg AAE/g DW), and the lowest DPPH IC50 (1.10 μg/mL), indicating strong antioxidant activity. ANOVA showed that the pineapple peel and cocoa pod ratio significantly affected all responses (p ≤ 0.05). Model validation demonstrated good predictive accuracy with errors below 8%, while FTIR analysis confirmed the presence of phenolic and flavonoid functional groups. These findings demonstrate the potential of UAE to produce antioxidant-rich extracts from fruit processing by-products, promoting waste valorisation and sustainable resource utilisation.