A critical review of the extraction methods of value-added products derived from rambutan (Nephelium lappaceum) seeds

Abstract

Rambutan processing discards the peels and seeds as fruit by-products constituting almost 50 percent of the total fruit weight. In the Philippines, the country’s total rambutan fruit production volume reached 8,312 metric tons in 2020 which usually ends up in landfills, contributing to municipal solid waste. Production of value-added products (VAPs) is an effective agro-waste management approach to valorize rambutan seeds for food and non-food applications. This paper aimed to assess the extraction methods of rambutan seed VAPs, the benefits and limitations of each extraction technique, and the strategies for optimizing the operational conditions to ensure maximum yield. Conventional extraction methods heavily rely on the use of large amounts of organic solvents which pose safety and environmental risks, typically requiring long extraction time with low yield. In this paper, digestion, solvent extraction, mechanical oil extraction, maceration, and Soxhlet extraction were the conventional methods assessed. Recently, development towards addressing these limitations is the focus of non conventional extraction methods such as supercritical fluid, ultrasound-assisted, and enzyme-assisted extraction. These extraction methods are environment-friendly and can be employed to produce VAPs, often with higher extraction yield at shorter extraction time. Choosing the most suitable extraction method is a challenging task as it weighs multifarious considerations in terms of economic value, technological cost, extraction time, environmental issues, and feasibility of scaling up. Strategies to improve extraction yield include pretreatments and optimization studies through response surface methodology. The development of smart, low-cost, and greener extraction methods addresses the environmental issues and low extraction efficiencies of conventional methods.