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RETICULATED POLYMERS FOR ELIMINATION OF UNSTABLE PROTEINS
Summary of result obtained in the first project period
In order to eliminate the unstable proteins from wine, every year in Europe about 10.000 tons of bentonite are used. Bentonite is a type of clay, mainly originated from other continents, that is suspended into wine where it absorbs proteins; after settlement, it is eliminated by racking, centrifugation and filtration to obtain a clear and stable wine. Bentonite fining is effective and inexpensive, however wine producers dislike it because it tends to reduce and modify the aroma and the taste of wine, and because the treatment often implies significant product losses. Moreover, the transport and distribution of such quantities of bentonite from continent to continent makes use of significant energetic resources.
Stabiwine project aims to exploit for this purpose the characteristics of polymers based on starch derivates, able to interact with proteins. The elemental bricks of these polymers are molecules of glucose and other sugars, obtained from cereals, and linked together in circular or linear compounds. The dextrins can be chemically bound together into reticulated polymers with different dimension, shape and charge, by varying the ingredients, their proportion and the reaction conditions.

The research activity is focused on the identification of a biopolymer effective for protein removal, without negative effects on wine quality, composed exclusively by harmless and natural components, and with production cost compatible with wine industry standards. A multidisciplinary approach was adopted, where chemists were synthetizing several types of polymers with variable combinations of monomers, cross-linkers, functionalizing agents, catalysts and reaction conditions; the polymers were tested by wine experts on different wines, varying usage modalities, to assess their suitability to become a processing aid for winemaking; toxicologists were advising on potential risk for human health or environment of polymer components; industrial partners were suggesting routes to simplify future industrial production and distribution, and to limit production cost; all these inputs were jointly discussed and originated ideas for further improvement of polymers by the chemist, with the consequent restart of the virtuous loop.

Several dozens of polymers of different nature were synthetized, and evaluated for their effectiveness in real wines.
First, research identified the components able to create polymers with the right charge and shape, able to interact with the specific unstable protein fraction of wine, mainly composed by chitinases and TLP proteins. Progressive improvements led to a polymer exclusively constituted by natural compounds, and with significant and consistent removing action on wine proteins.
In a second step, the proportion among polymer components varied, and this brought to a powder that, once added to wine in a batch treatment, is able to remove wine proteins to an extent comparable to that of a high quality bentonite.
Very interestingly, the treatment with the new polymer, even at high dosage, does not seem to affect the concentration of wine volatile compounds, neither it is perceived by expert sensory panels. Conversely, the polymer might pay a positive role against wine oxidation; moreover, its effectiveness is scarcely dependent from wine characteristics, like pH, so allowing its use on a wide range of wines.

The following months of activity will be devoted to the understanding of the mechanisms of interaction of the new polymer with wine proteins, and with other native or added wine components like metals, phenols, other types of proteins, etc. Swelling characteristics and lees volume after batch treatment will be optimized.
The possibility to use the new polymer in a column treatment will also be explored.
The industrial scale-up of the polymer production process, and the activation of the authorization procedure as processing aid for winemaking, will also be an important part of the actions. Additionally, demonstrative trials in different European regions are planned, to evaluate the new practice in real winery conditions. The advantages offered toward better sustainability will be assessed in comparison with bentonite fining.

Results obtained till now encourage the expectation of the wine industry to eventually find an effective and affordable alternative technology to bentonite fining: the use of a reticulated biopolymer, obtained from natural and renewable row matters, specific against unstable proteins, and without alteration of the original wine composition. Possibly, the new processing aid will offer side advantages on wine quality and will reduce wine loss accompanying bentonite fining, with gain in competitiveness for wine producers. Notably, being the new technology very simple and inexpensive, it will be accessible to winery with any size and location around Europe.



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