Optimization of ultrasound extraction of phenolic compounds from coconut (Cocos nucifera) shell powder by response surface methodology

Coconut is a tropical fruit largely consumed in many countries. In some areas of the Brazilian coast, coconut shell represents more than 60% of the domestic waste volume. The coconut shell is composed mainly of lignin and cellulose, having a chemical composition very similar to wood and suitable for phenolic extraction. In this work, the use of ultrasound to extract phenolic compounds from coconut shell was evaluated. The effect of temperature, solution to solid ratio, pH and extraction time were evaluated through a 24 experimental planning. The extraction process was also optimized using surface response methodology. At the optimum operating condition (30 °C, solution to solid ratio of 50, 15 min of extraction and pH 6.5) the process yielded 22.44 mg of phenolic compounds per gram of coconut shell.