Valorization of rambutan peel (Nephelium lappaceum L.) byproducts through pulsed electric field-assisted green extraction of pectin optimized by response surface methodology

Abstract

The global demand for sustainable food ingredients has driven interest in fruit by-product valorization into high-value compounds. Rambutan (Nephelium lappaceum L.) peel, an underutilised fruit by-product, contains abundant pectin, which is suitable for various industrial applications such as gelling and emulsifying agents. This study explored a green extraction strategy combining pulsed electric field (PEF) pretreatment with optimization by response surface methodology (RSM) to recover high-quality pectin while minimising thermal degradation and processing time. Three identified key factors influencing extraction performance, such as electric field strength, extraction time, and solid-to-solvent ratio, were optimized using a Central Composite Design (CCD). The optimum condition (20 kV cm⁻¹, 12.69 min, 30 mL g⁻¹) produced pectin with 4.37% yield, 8.76% methoxyl content, 75.72% galacturonic acid, and 65.66% degree of esterification, classifying it as high methoxyl pectin. Structural characterisation via Fourier Transform Infrared Spectroscopy confirmed functional groups consistent with commercial standards, while Scanning Electron Microscopy revealed extensive cell wall disruption induced by PEF. This approach not only enhances extraction efficiency but also provides an eco-friendly valorisation pathway for tropical fruit waste, contributing to circular economy practices in the food industry.