Fungal chitosan is a wine additive used to eliminate unwanted microorganisms that alter the quality of wines. Although authorized by the OIV, biocompatible and renewable, chitosan is little used by winemakers because doubts persist about its effectiveness and its effects on wine taste and quality. The CHITOWINE project aims to clarify the spectrum and the antiseptic mechanism of chitosan in order to propose new or improved modes of use.
Grape juice and wine harbor complex microflora that usually contributes to the final quality of the wine. However, an imbalance of this microflora may cause the formation of undesirable compounds or unwanted fermentations. These deviations tarnish the image of the product and hijack buyers, often permanently. The most common method for preventing or eliminating wine spoilage microorganisms is the addition of sulfur dioxide (SO2). However, the use of SO2 can cause unwanted odors and headaches in many people. In addition, SO2 is one of the 14 priority food allergens in Europe and the authorized doses will be downgraded in the future. Furthermore, sulfites do not always avoid the risk of organoleptic deviations due to the emergence of resistant strains. <br />Alternative molecules or antiseptic methods are therefore essential. To this end, the addition of fungal chitosan in wine has been authorized since 2009 (OIV/OENO 338A/2009). However, it is currently little used, because random results and adverse effects on later stages of winemaking and on wine quality have been reported. It is currently not allowed in organic farming, and chitosan-treated wines cannot be marketed in some countries as decision-making bodies have indicated that further studies are needed. <br />The CHITOWINE project aims to (i) better define the antiseptic spectrum of chitosan in wine, taking into account the genetic diversity within and between microbial species, (ii) identify, at least in part, the active molecules of chitosan, (iii) propose analytical methods to assist in the use of chitosan and (iv) develop improved use recommendations that will maximize antiseptic efficacy and clearly indicate the benefit/risk ratio for each type of wine.
In 2018, during the first year of the ANR project, an important screening work will be carried out to determine (1) the antiseptic spectrum of chitosan among the microbial species of wine and (2) if less sensitive or even resistant strains exist at within the species studied. Several model strains will then be chosen for further study.
With these strains, we will analyze the influence of different reaction parameters on the treatment effectiveness (wine parameters, chitosan lots, dose, contact time, population level ...). Different complementary experimental designs will be realized for this purpose. This work will be done in collaboration between the Oenology Unit and Microflora (ADERA).
At the same time, different homogeneous fractions of chitosan (in terms of MW and DA) will be prepared and characterized by Institut Pascal, and their antiseptic activity will be assayed on the selected model strains.
The project began in January 2018. Work is in progress.The screening has been completed and is being analyzed. We begin experiments aiming at better understanding the mode of action of chitosan with selected model strains.
To come up
..Brasselet C., G. Pierre, P. Dubessay, M. Dols-Lafargue, J. Coulon, J. Maupeu, A. Vallet-Courbin, H. De Baynast, T. Doco, P. Michaud, C. Delattre. 2019 Modification of chitosan: How generating new functional derivatives? Applied Sciences, 9(7), 1321; doi
Fungal chitosan is a polysaccharide made up of glucosamine and N-acetyl-glucosamine and derived from chitin-glucan from Aspergillus Niger or Agaricus bisporus. It has been authorized as an antiseptic agent in wine in 2009 (OIV). Only the fungal chitosan is allowed in wine, with total exclusion of those extracted from crustaceans. At the maximum dose of 10g/hl, it was shown to allow to efficiently eliminating Brettanomyces bruxellensis, a volatile phenol producing yeast and the main spoilage agent in red wines. Although the fungal chitosan is highly renewable, biocompatible (ADI equivalent to sucrose) and non-allergenic, winemakers very often prefer to use sulfites (SO2), though they are classified as priority food allergens. Indeed, fungal chitosan appears as a poorly reliable product because of many conflicting reports and advices on its efficiency and on its side effects towards beneficial wine microorganisms or wine taste. These contradictions could be explained by the heterogeneity of the fungal chitosan lots traded, the diversity of the wines (chemical composition, winemaking route chosen) but also by the recently highlighted huge genetic diversity prevailing in wine microbial species.
The CHITOWINE project is based on the collaboration of three academic partners, a technology transfer unit and an industrial partner. It primarily aims to better demonstrate the potential and limitations of fungal chitosan use as an antimicrobial agent in wine. The work will first enable to better define the spectrum of fungal chitosan through the screening of a large microbial collection representative of the inter- and intraspecific diversity of wine ecosystem (16 species, 200 strains). The chemical characteristics essential to the antiseptic activity of fungal chitosan (degree of acetylation, molecular weight, solubility) and the influence of extrinsic parameters of reaction (pH, temperature, dose) will be evaluated. In addition, the physiological effects of chitosan will be sought through a battery of biochemical, microscopic and transcriptomic tests, to identify, if possible, the molecular targets of chitosan and to understand the sensitivity differences observed, between species and between strains in the same species, and improved use recommendation will be proposed and evaluated. The need for additional treatments (filtration, enzymatic treatments) to completely eliminate B. bruxellensis and the efficiency of fungal chitosan for solving other microbiological issues in winemaking will be examined. The consequences of chitosan treatment on the colloidal stability and organoleptic properties of wines will be studied. Analytical methods to guide chitosan use (for checking the quality of chitosan lots, for the detection of resistant strains, for determination of chitosan residue after wine treatment) will be developed and optimized.
The results will be widely disseminated in an efficient and modern way to a wide audience (scientists, students, wineries wine professions, oenological product purchasers, decision-making bodies such as OIV). If the use of fungal chitosan confirms that it is safe and efficient for treating specific oenological contamination (B. bruxellensis or other), it could, in these specific cases, efficiently replace sulfur dioxide as an antimicrobial agent. This would contribute to lower the dose of sulfites in wines and to consolidate the current approach for more natural and sustainability in the wine industry (challenge 5, focus 4). The economic and societal benefits will be important since this sector is the second largest exporting sector in France and wine a main symbol of French art of living.
Madame Marguerite DOLS-LAFARGUE (Unité de recherche Oenologie)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
UMR SPO UMR Sciences pour L'oenologie
IP, GePEB Institut Pascal, Axe GePEB, UMR CNRS 6602
U Oeno Unité de recherche Oenologie
Help of the ANR 633,880 euros
Beginning and duration of the scientific project: December 2017 - 48 Months