Comparison Between the Kinetics of Conventional Maceration and A Cyclic Pressurization Extraction Process for the Production of Lemon Liqueur Using A Numerical Model

The purpose of this study was to compare two extraction processes for the production of lemon liqueur (limoncello)—the traditional maceration of lemon peels and a cyclically pressurized extraction process also known as rapid solid-liquid dynamic extraction (RSLDE) that uses a Naviglio extractor. To evaluate the extraction efficiency of the two processes, dry matter obtained by the evaporation of the extracts was used to construct kinetics curves. The dry matter was directly proportional to the amount of the active principle (terpenes) extracted and consequently to the total concentration. Alcoholic extracts were analysed by gas chromatography (GC) to monitor the extraction kinetics for major components of the terpene fraction and for minor components of essential oils. Moreover, alcoholic extracts were analysed by UV spectrophotometry to identify the more abundant chemical species, while the organoleptic tests (i.e., a consumer test) performed on the final product (limoncello) provided an indication of the taste of the final product and revealed features undetectable with instrumental analytical techniques. To better understand the phenomenon considered, a numerical simulation was performed to evaluate and compare the matter flow of extractable compounds during the process.