## 1 Introduction  
Chitin is a linear polymer composed of units of \(N\)-acetyl-D-glucosamine (acetylated unit) and D-glucosamine (deacetylated unit), found in natural sources (i.e., the exoskeleton of arthropods, cell walls of fungi) in association with proteins, minerals and pigments. The removal of these elements, in order to obtain pure chitin, is realized in three steps: the demineralization of the raw material, its deproteinization and its decolorization [1]. Through a process of deacetylation, which consists in the removal of acetyl groups, chitin can be transformed into its derivative chitosan. The amount of acetylated units remaining reveals the efficiency of the transformation of chitin into chitosan and determines their so-called degree of acetylation (_DA_--usually employed for chitin) or degree of deacetylation (_DD_--usually employed for chitosan). If the product resulting from this transformation contains more than 50% of acetylated units (_DA_\(>\) 50% and _DD_\(<\) to 50%), it is called chitin, while if it contains more than 50% of deacetylated units (_DA_\(<\) 50% and _DD_\(>\) to 50%) it is called chitosan [1]. Within a source, chitin can be found in three different polymorphs: \(\alpha\), \(\beta\) and \(\gamma\), depending on the parallel, antiparallel or alternated orientation of the fibers,respectively [2]. \(\alpha\)-chitin is the most abundant polymorph and if found in fungi, insect exoskeleton and shells of crustaceans, while \(\beta\)- and \(\gamma\)-chitin are uncommon and are found in squid pens and in beetles (family _Lucanidae_), respectively [3]. Both chitin and chitosan, due to their biodegradability, biocompatibility and low toxicity, are widely studied in the biomedical and pharmaceutical research fields. However due to the high number of acetyl groups, which form strong hydrogen bonds, chitin is insoluble in water and in most of the common organic solvents such as acetic acid [2]. As a consequence, the use of chitin is limited, and it is often converted to its derivative chitosan. Chitosan has a pKa value of 6.2, meaning that when the pH is above this value, its amino groups (NH\({}_{2}\)) are protonated (NH\({}_{3}^{+}\)) and chitosan becomes cationic and soluble. The cationic nature of chitosan is rather special, since most of the natural polysaccharide are either neutral or negatively charged when dissolved in acidic environment. This property allows chitosan to form electrostatic complexes with negatively charged polymers [4]. Furthermore, chitosan presents a high number of reactive amino (NH\({}_{2}\)) and hydroxyl (OH) groups, which can be easily chemically modified to produce chitosan derivatives [5]. Commercially, chitin is mainly extracted from crustaceans and, in a minor part, from fungi. However, the interest in insects as an alternative source of chitin and chitosan is growing [6]. The investigation of alternative renewable sources is an active field of research that could not only lead to their commercialization, but also the identification of products with different properties and applications. When new sources are identified, it is necessary to characterize the physicochemical properties of the resulting product chitin and investigate its stability over the years. In fact, all the sources (i.e., the exoskeleton of arthropods) are usually composed of the same elements (i.e., chitin, proteins, minerals and pigments), whose relative abundance is usually source-specific. However, the precise amounts can vary due to environmental causes and lead to chitin with different physicochemical properties. [PERSON] et al. [7], for example, reported that within the same source (in this case crustacean shells), the content in minerals, proteins and chitin, as well as the physicochemical properties of the latter, can differ based on the season when the shells are collected. In another study, [PERSON] et al.