Kinetic modeling and process intensification of ultrasound-assisted extraction of d-limonene using citrus industry waste

Citrus limetta is a widely-processed fruit that generates 40 % peel waste involving considerable constraints for waste management. Citrus limetta peel is a rich source of essential oil, especially d-limonene, commonly used as a fragrance and flavor ingredient. This study investigated the application of ultrasonication as a process intensification tool with improved extraction-efficiency. Pelegs mathematical model was used to study the kinetics of ultrasound-assisted extraction (UAE) of d-limonene. The use of UAE reduces the total extraction time to 20 min compared to 185 min in a conventional process. In UAE, the highest extraction yield of d-limonene (32.9 mg/g, 97 %) was obtained using hexane as food-grade solvent, biomass:solvent ratio of 1:10, 2 mm particle size, agitation speed 300 rpm, temperature 60 degrees C with ultrasonic power 80 W, 50 % duty cycle and frequency 25 kHz. Analysis and characterization of the extract were carried out using HPLC, GC-MS, and FTIR. Also, the surface morphology of raw material after extraction was studied using SEM analysis. The acceptable agreement was seen in the calculated values of C-eq from Pelegs mathematical model and actual experimental results of extracted d-limonene. UAE stands as a fast, efficient, and economical method for the extraction of d-limonene from the fresh sweet lime peel.

Automated summary

This study investigated the use of ultrasonication as a process intensification tool for the extraction of d-limonene from Citrus limetta peel. By using ultrasonic-assisted extraction, the extraction time was reduced to 20 minutes compared to 185 minutes in a conventional process. The highest extraction yield of d-limonene was achieved using hexane as solvent, biomass:solvent ratio of 1:10, 2 mm particle size, agitation speed 300 rpm, temperature 60 degrees C, ultrasonic power 80 W, 50% duty cycle and frequency 25 kHz.