A group of researchers of the University of Aveiro, Portugal, created an ecological wine conservative which consists of a film prepared from fungi and from shrimp by-products. This novel solution is healthier, environmental friendly, and causes neither allergies in consumers nor changes in the wine properties.
But let’s start from the beginning. Basically, the films were made of chitosan obtained either from shrimp exoskeleton* waste or from certain fungi. Well, simplifying these concepts, the exoskeletons of shrimps are composed by chitin, and it can be converted into chitosan (a polysaccharide) by a chemical procedure (partial deacetylation).
Shrimp industries generate about 45-55% of the weight of raw shrimps in exoskeleton waste. From this by-product, it is possible to extract chemically 15-25% of chitosan. Besides, chitin is also the major component of fungi cell walls. So, two relevant source for chitosan are the shrimp exoskeleton waste and certain fungi.
Obtaining chitosan from shrimps by-products.
Chitosan films consist of a cross-linked network of chitosan. Genipin, a molecule that comes from Gardenia fruits, is a natural cross-linking agent, and was added to chitosan to improve the water stability of chitosan films. Thus, it was possible to obtain chitosan films with antioxidant and antimicrobial properties, as well as with ability to hydrate but not to solubilize.
After alcoholic fermentation, the wine was transferred to glass bottles, and three lots of the same wine were prepared: (1) with addition of one chitosan-genipin film; (2) with addition of SO2; (3) with addition of no preservative. Before wine analyses, chitosan-genipin films were removed from the respective wine lot. The three lots of wines were analysed in relation to their sensorial properties, volatile composition, colour, phenolic compounds, ability to remove iron ions, and allergenicity.
Wines with addition of chitosan-genipin films showed organoleptic properties similar to those prepared using SO2, as well as the overall volatile character. Also, chitosan films could remove iron ions, which were responsible for promoting oxidative reactions and consequently wine browning. Thus, when iron ion was removed from wine, researchers could note an inhibition of oxidative reactions and microbial growth. Even though, the presence of chitosan-genipin films promoted some chemical reactions, which led to the production of volatile compounds with positive wine flavours.
Given this promising results, researchers protected this novel preservative procedure by a patent, and they believe that it could be easily implemented at an industrial scale with no additional costs. Indeed, Dão Sul Company (a Portuguese wine company) could already produce three thousands liters of white wines and sparkling wines using this ecological methodology.
In sum, Portuguese researchers could develop a circular economy technology that uses a by-product of the food industry to produce a value added product - chitosan-genipin films. In turn, the application of chitosan-genipin films in winemaking showed to be an innovative, green and environmentally friendly alternative to SO2, being an effective wine conservative and causing no allergenicity problems to consumers.
*an exoskeleton is the external skeleton that supports and protects an animal's body.
References:
Nunes, C., Maricato, É., Cunha, Â., Rocha, M.A.M., Santos, S., Ferreira, P., Silva, M.A.,Rodrigues, A., Amado, O., Coimbra, J., Silva, D., Moreira, A., Mendo, S., Lopes Da Silva, J.A., Pereira, E., Rocha, S.M., Coimbra, M.A. Chitosan-genipin film, a sustainable methodology for wine preservation. Green Chem. 18, 5331–5341. (2016) doi: 10.1039/c6gc01621a.
Santos, M.C., Nunes, C., Saraiva, J.A., Coimbra, M.A. Chemical and physical methodologies for the replacement/reduction of sulfur dioxide use during winemaking: review of their potentialities and limitations. Eur Food Res Technol. 234, 1-12. (2012) doi: 10.1007/s00217-011-1614-6.
Coimbra, MA, Nunes, C, Maricato, É, Cunha, Â, Barroso, S & Silva, JA 2011, Processo de produção de vinhos sem adição de anidrido sulfuroso por utilização de filmes com base em quitosana, PCT/PT2012/000043
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