Use of chitosan as a secondary antioxidant in juices and wines
Abstract
Chitosan is a polysaccharide produced from the deacetylation of chitin extracted from crustaceous and fungi. In winemaking chitosan is mainly used in the clarification of grape juice and wine, stabilization of white wines, removal of metals and to prevent wine spoilage by undesired microorganisms. The addition of chitosan to model wine systems was able to retard browning, reduce levels of metallic ions (Fe and Cu) and to protect varietal thiols due to its antiradical activity1. The present experiment was planned in order to evaluate the use of chitosan as a secondary antioxidant at three different stages of Sauvignon blanc fermentation and winemaking. Sauvignon blanc juices from three different locations were obtained at a commercial winery in Marlborough, New Zealand. One lots of grapes was collected from a receival bin and pressed into juice with a water-bag press, and a further juice sample was collected from a commercial pressing operation. Chitosan (1 g/L, low molecular weight, 75 – 85% deacetylated) was added to the juice after pressing, after cold settling, after fermentation, or at all these stages. Controls without any chitosan additions were also prepared. The fermentation was carried out using Saccharomyces cerevisiae EC 1118, with 700 mL of juice at 15°C. Analysis by GC-MS of C6 aldehydes and alcohols in the juices revealed that the addition of chitosan to the pressed juice lowered the concentration of E-2-hexenal, a known precursor of varietal thiol 3-mercapto hexanol, loss with cold settling. The juices that had chitosan added after pressing had their potential to form 3MH and 3MHA greatly lowered (by up to 90%), in comparison to control juices, and juices to which chitosan had been added after cold settling or after fermentation. In conclusion, the addition of low molecular weight chitosan as antioxidant or clarifying agent is not advised in the initial stages of winemaking if the higher levels of varietal thiols in the final wine are desired.
1 Chinnici, F., Natali, N., & Riponi, C. (2014). Efficacy of chitosan in inhibiting the oxidation of (+)-catechin in white wine model solutions. J Agric Food Chem, 62(40), 9868-9875.
Issue: Macrowine 2016
Type: Poster
Authors
*University of Auckland