An Eco-Friendly High-Pressure Biorefinery Approach for the Recovery of Valuable Compounds from Cashew Nut Testa Shell (Anacardium occidentale L.)

Abstract

The cashew agroindustry generates substantial by-products that are often improperly used. Cashew nut testa shell (CNTS) has attracted interest due to its elevated fatty acid contents and phenolic compounds, raising the relevance of environmentally friendly extraction techniques for its recovery. CNTS was submitted to high-pressure (supercritical fluid extraction, SFE; pressurized liquid extraction, PLE; and subcritical water extraction, SWE) methods compared to traditional low-pressure (Soxhlet and maceration) techniques. Supercritical fluid extraction with CO₂ as solvent was selective to recover fatty acids, such as palmitate (12.63 mg g⁻¹), linoleic (39.03 mg g⁻¹), stearic (29.65 mg g⁻¹), and oleic (25.61 mg g⁻¹) acids, as well as behenic (46.42 mg g⁻¹) and erucic (28.00 mg g⁻¹), quantified by GC–MS. In contrast, the ethanolic and aqueous extracts, by pressurized liquid and subcritical water extraction, presented polyphenols like catechin, epicatechin, and procyanidin identified by UPLC-PDA-ESI-QDa, known for their high antioxidant potential and biological activities. In addition, fractions of proteins and sugars were also recovered. Considering the different compounds in the raw material, sequential extraction routes were conducted to fractionate the CNTS and provide different products from an underestimated raw material. This novelty increases the value of the cashew processing chain, enhancing further applications of the extracts in the food, chemical, and pharmaceutical industries.

Graphical Abstract