Laboratory Production of Lemon Liqueur (Limoncello) by Conventional Maceration and a Two-Syringe System To Illustrate Rapid Solid–Liquid Dynamic Extraction

Two experimental techniques of solid–liquid extraction are compared relating to the lab-scale production of lemon liqueur, most commonly named “limoncello”; the first is the official method of maceration for the solid–liquid extraction of analytes and is widely used to extract active ingredients from a great variety of natural products; the second is a two-syringe system based on a Naviglio extractor, which represents a new solid–liquid extractive technology called rapid solid–liquid dynamic extraction (RSLDE) that changes the philosophy of the process of solid–liquid extraction. Maceration is based on the principle of diffusion (Fick’s law) that depends mainly on temperature; in fact, to increase the speed of maceration, heating of the system is required. In the case of RSLDE, the principle is based on the generation, in the presence of an appropriate solvent, of a negative pressure gradient between the outside and the inside of the solid matrix, followed by a sudden restoration of the initial conditions of equilibrium, which induces the forced extraction of compounds not chemically bonded to the matrix; consequently, the extraction can be performed at room temperature. In the experiment described, students evaluate the efficiency of extraction by the two methods. This laboratory experiment can be used in a food science laboratory course for secondary schools and for university students.