A comprehensive approach to pecan nut valorization: Extraction and characterization of soluble and insoluble‐bound phenolics

Abstract Pecan nuts are known for having high‐phenolic content and antioxidant capacity. In the present work, exhaustive extraction and LC–MS analysis of the soluble (SP) and insoluble‐bound phenolics (IBP) from pecan nut cake were performed. Its SP fraction (1.72 mg/g) is composed of ellagic acid, its glycosylated derivatives and gallic acid. The IBP fraction (2.20 mg/g) includes hydrolysable tannins derived from ellagic and gallic acids and proanthocyanidins from (epi)catechin and (epi)gallocatechin monomers; comprising 56% of the total phenolic content in pecan. Ellagic acid is the main phenolic found in both extracts corresponding to 1.96 mg/g of pecan nut cake. In addition, the extraction of the main SP found in pecan nut cake (ellagic acid and its derivatives) was optimized. The optimal conditions for SP extraction (40% ethanol, 85°C, and 60 ml/g) were able to extract 77% of the total ellagic acid found in pecan nut cake. In addition, the optimized condition for SP extraction (without the heated acid and methanol applied in IBP extraction) released a substantial quantity of ellagic acid and its glycosylated derivatives that are likely noncovalently absorbed in the pecan matrix. Therefore, the extraction process proposed in the present work shows considerably high efficiency using aqueous ethanol and high temperatures for the obtention of phenolics, particularly of ellagic acid, from pecan nut cake.