The controversial relationship between chitosan and the microorganisms involved in the production of fermented beverages

Chitosan is a promising antimicrobial agent available in the beverage industry, because it ensures the control of a wide range of spoilage microorganisms. As chitosan does not alter the characteristics of fermented beverages, it is nowadays widely employed in the wine sector. In this work, an exhaustive chemical characterization of 12 commercial chitosans was performed in accordance with the OIV methods. These analyses made it possible to confirm or determine the animal or fungal origin of the 12 samples. Furthermore, ionic chromatography coupled with an amperometric detector (IC-PAD) confirmed peculiar polysaccharide profiles for fungal and animal-derived chitosans. The antimicrobial activity of chitosans was evaluated against the microorganisms involved in beverage fermentation or capable spoil wine, beer and cider. Chitosans were tested in static and stirred conditions, in a synthetic medium that reproduces fermented beverage conditions, to discriminate against the physical settling of cells and their specific antimicrobial activity. Moreover, the activity of the soluble portion of chitosan was checked by inoculating microorganisms in the media after chitosans removal. The results highlighted the different sensitivity of microorganisms to chitosans, allowing selective control of spoilage agents. However, the yeast and bacteria involved in fermentation were damaged by chitosan, and the synthetic media treated with this molecule showed a less fermentative aptitude. These results suggest that chitosan is a promising tool in fermented beverage production, but an in-depth study of the biochemical interaction between chitosan and food microorganisms is necessary