Chitosan as bentonite replacement for white wine fining

Alternative methods have been proposed to counteract the drawbacks [1, 2] of bentonite, traditionally used to lower the risk of wine haze. Enzymatic degradation of wine proteins [3], ultrafiltration [4] and novel fining agents such as negatively charged polysaccharides like carragenans [5] have been proposed. The addition of chitin [6] as a specific agent for the removal of chitinase proteins would be a good choice for wine fining, but chitin is not allowed by EU regulation. Fungoid Fungine chitosan [7] from Aspergillus niger is the only type of chitosan accepted in winemaking to control Brettanomyces spp population [8], and to remove ochratoxin A and metals [9]. The effects of chitosan on wine have been insofar focused on evaluating antioxidant activity [8] and removal of procyanidins and cinnamic acids [10]. Due to its structural similarity with chitin and the activity of chitinases under wine conditions [11], chitosan could be capable to interact with grape chitinases and to remove them. This work aims to fill the lack of data concerning the effect of chitosan on the removal of proteins from wines. One Moscato wine was treated with two chitosan powders, which were characterized for the deacetylation degree, the molecular weight and the solubility. After filtration, the wine was analysed for its haze potential, proteins, total polyphenol index, Folin-Chocalteu. HPLC analyses were carried out to outline any interaction with organic acids and phenolics. Finally, GS-MS analysis quantified the free and glycosylated aroma compounds. The results showed a significant reduction of protein content and haze potential, thus indicating a positive action of chitosan as fining agent. Negligible reductions interested the total polyphenols, while significant depletions of flavons, flavan-3-ols and cinnamic acids occurred. Tartaric and malic were affected also, as like as free aroma compounds, whilst no difference interested the glycosylated forms.