Sustainable synthesis and optimisation of ethyl oleate from high oleic acid waste: a pathway to valorise industrial byproducts

Ethyl oleate (EO) is a versatile compound with several industrial applications, such as a vaccine adjuvant, an emollient in cosmetics, and a key component in food products as an additive used for pretreatment in preservation processes such as drying, while preserving valuable nutrients. Ethyl oleate is primarily synthesised from edible oils, which raises concerns regarding competition with food production. This study proposes the use of a high oleic acid waste (HOW) obtained from industrial pipelines as a raw material for EO production, by transesterification with ethanol and using sodium hydroxide as a catalyst. The effects of the HOW : ethanol ratio and recirculated EO addition on both yield and purity levels were investigated. An HOW : ethanol ratio of 6 : 1 (w/w) and a 10% (w/w) of EO recirculated addition resulted in the highest purity (86.16 ± 0.04%) and yield (96.35 ± 0.01%). The resultant EO samples were characterized towards its composition and physicochemical properties. The study highlights the sustainable valorisation of industrial waste. This approach avoids competition with the food chain and offers an eco-friendly method to produce EO for various industrial applications, particularly in food science.