Ultrasonic cavitation assisted deep eutectic solvent extraction of pectin from waste sweet lime peel: Statistical optimization and energetic analysis

Abstract

The present work investigates the extraction of pectin from the waste sweet lime peel (SLP) using deep eutectic solvent (DES), Choline chloride: Citric acid, using an ultrasonic cavitation-assisted process. Box Behken Design (BBD) in response surface methodology was adopted to optimize the process variables for maximum yield of pectin and understand the interactive effect. An assessment of the physicochemical properties and energy requirements were also conducted to evaluate the feasibility of the extraction process. The BBD analysis with desirability function resulted in a maximum pectin yield of 37.21 % and a degree of esterification of 85.49 % under optimized conditions of time: 34.55 min, power amplitude: 60 %, solid/liquid ratio: 1:30 and DES to water ratio of 1:5.38. The ANOVA assessment of BBD revealed the significance of the process variables on pectin extraction in the decreasing order as DES to water ratio>solid to liquid ratio>time>amplitude. The thermal, functional group, and elemental analysis indicate the extracted pectin to be similar to commercial pectin. The energetic study revealed that cavitation-assisted extraction has an energy savings of 0.718 KJ/g compared to conventional extraction. Therefore, the results show that the present extraction strategy can be a cost-effective and eco-friendly process that has the potential for scale-up. The process also projects a crucial valorisation route for waste SLP.