# Chitin and Chitosan in the Alcoholic and Non-Alcoholic Beverage Industry: An Overview
## 3 Chitosan Applications in Beverages
### Extending the Shelf-Life  
There is an increase in consumer demand for safe and healthier products; in this way, an increase in the consumption of freshly processed products has been observed, and the beverage industries need to search for compounds to extend the shelf life of these products by application of natural products. The antimicrobial and antioxidant activity of chitosan permits its application to extend the beverage shelf life, as shelf life is constrained by microbial spoilage and oxidation [57; 82; 83; 84]. The antioxidant activity of chitosan is related to the scavenging effect on free radicals [83; 85; 86]. Chitosan deacetylation degree influenced its antioxidant activity, and this activity rises with unsubstituted amino groups [57]. Therefore, the antioxidant activities of chitosan increased with an increase in deacetylation degree [87]. The molecular weight of chitosan has also been described to have a main effect on its antioxidant activities, with low molecular weight (16 to 190, 127 kDa), chitosan having more marked scavenging effects on superoxide and hydroxyl radicals than those with high molecular weight (>300 kDa), probably related to the compact structure of the chitosan with a high molecular weight that limited the antiradical activity of the hydroxyl and amino groups [88,89]. For antimicrobial activity, the most important factors are the type of microorganism [84,90,91,92], the chitosan charge density, concentration, molecular weight [84,92], hydrophilic/hydrophobic characteristics, chelating capacity, and the degree of deacetylation [84]. It has been suggested that the polycationic nature of chitosan that forms from acidic solutions below pH 6.5 is a crucial factor. A higher positive charge density leads to strong electrostatic interaction. Therein, the positive charge is associated with the deacetylation degree of chitosan [93]. The chitosan antifungal and antimicrobial activity against different fungi, Gram-positive and Gram-negative bacteria, is related to the chitosan cationic properties in an acidic media at pH values below chitosan pKa. As protonated amino groups bind to the negatively charged carboxyl groups, such as bacterial cell wall surface peptidoglycan, altering their barrier properties, leading to permeabilization and destruction of external membranes [94]. Therefore, Chitosan is most active at the fungi or bacteria cell surface leading to permeabilization [95,92,96,97,95,98,99], which results in leakage of intracellular material and consequently in cell death [96,98,99]. Challenges in the wine industry are preventing wine spoilage, maintaining wine color, and avoiding aromatic defects by limiting oxidation. Sulfur dioxide may be added to achieve these objectives; however, sulfur dioxide may have adverse effects on human health, such as pseudo-allergies [100,101], and winemakers are, therefore, trying to limit the use of sulfites (mainly sulfur dioxide) in the winemaking process [102,103,14]. Natural products such as metabolites produced by living organisms and/or those naturally occurring in nature have been studied, aiming to prevent microbial spoilage, and thus are an appropriate alternative to the use of synthetic products, such as sulfur dioxide [104]. Among the products studied, chitosan meets these requirements, as several activities have been demonstrated for different types of chitosan, namely as a preservative and an antimicrobial agent [105,106,107,21,85]. It has already been shown that chitosan has antimicrobial effects against bacteria (lactic acid bacteria and acetic acid bacteria), fungi, and spoilage yeasts, such as _Brettanomyces_ sp., during wine storage [23,25,107]. However, it is permissive for the growth of _Saccharomyces_ species [22,25,108]. In this way, OIV- OIV/OENO 338A/2009 resolution [12] allows the use of fungal chitosan to control the development of undesirable microorganisms, namely _Brettanomyces_ sp at a maximum dose of 10 g/hL.