Optimization and scale-up of the extraction process of added value compounds from by-products of the walnut from Nerpio (Juglans regia L.)

Abstract

The study optimizes and extends the extraction of polyphenols from by-products of the walnut from Nerpio (Juglans regia L.), thereby addressing the underutilization of agricultural waste and contributing to the development of a circular economy model. The by-products, including walnut shell and walnut tree pruning, were processed to extract high added value polyphenols. The optimal laboratory conditions were an ethanol solution with an alcohol strength of 60°, a solid/solvent ratio of 1:4, a particle size of 6 mm, a temperature of 25 °C and an extraction time of 1.5 h. The scalability of the process was validated on a semi-industrial scale, resulting in a 35.4 and 23.3% extraction yield for walnut shell and winter pruning, respectively. Extraction yields at a semi-industrial scale were higher than those obtained in the laboratory. The extracted polyphenols included ellagic acid, gallic acid and flavonoids, which have antioxidant, antimicrobial, anticarcinogenic, antimutagenic and cardioprotective activities. The process demonstrated technical feasibility, with potential applications in biomedicine, cosmetics and the food industry. This method enhances the value of walnut by-products from Nerpio, increasing their market value while promoting sustainable agricultural practices.