# Statistical Analysis Applied to the Production of Mirto Liqueur
## 1 Introduction  
_Myrtus communis_ L. (myrtle) is a wild aromatic plant belonging to the _Myrtaceae_ family [1]. The genus _Myrtus_ is the only spontaneous genus in Europe, represented by the _M. communis_ species [2]. It is an evergreen species of the Mediterranean scrub, known for its summer flowering, the intense green color of its leaves, and their characteristic resinous aromatic scent. It grows naturally in some Mediterranean areas, such as the coastal regions of Southern Italy, particularly Sardinia [3]. Myrtle is often used in the production of essential oils, for flavoring meat, and in the perfume and cosmetic industries. Its berries are industrially processed into liqueurs, producing more than three billion bottles each year. Additionally, the berries are commonly made into jams and sweets [4]. Typically, myrtle liqueur is obtained through the cold hydroalcoholic infusion of berries (red myrtle) or leaves (white myrtle) [5]. However, only a few authors have focused on optimizing the extraction parameters [6].  
Nowadays, multivariate analysis offers perhaps the best approach to establishing the optimized parameters in a process. Design of Experiments (DoE) has been successfully applied in various industrial and academic research fields, such as optimizing the recycling of waste cooking oils [7], customizing the synthesis of important pharmaceutical intermediates through Nazarov cyclization [8] and studying low-melting mixtures [9].  
Regarding the chemical composition of myrtle berries, the typical color and flavor are related to their polyphenol and volatile content [10]. Anthocyanins can undergo several transformations during the extraction procedure, showing limited stability depending on the pH, light exposure, water activity, oxygen, temperature, duration of processing, and storage conditions [11; 12; 13]. Thus, the extraction method plays a key role and strongly affects the chemical profile of the liquor [14].  
In accordance with European regulation CE n. 110/2008 [15] regarding spirit beverages, details concerning the extraction process for the production of _Myrtus_ liquor are outlined. The provided data, however, are somewhat broad and generic. For instance, the extraction time is specified to fall within a range of 15 days to 8 months, and the ethanol concentration required for extraction is stated to be a minimum of 40%. The present study aimed to provide a suitable statistical model to customize the chemical profile of myrtle liquor obtained by ethanolic extraction. Using a Design of Experiments (DoE) approach and multivariate analysis, the influence of the time, ethanol concentration, temperature, and the ratio between the amount of _M. communis_ berries and the extractant volume (v/w) on the amounts of anthocyanins, volatile compounds, and dry residues in the liqueur was assessed. The kinetics of the main parameters of the optimized extracts were also measured by fixed-wavelength UV-VIS spectroscopy and gas chromatography coupled with mass spectrometry (GC/MS). Our results could assist the spirit beverage industry in enhancing the extraction methods for liqueur production.