Use of biopolymers for sustainable stabilization of quality wines
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Descrizione del progetto
Project Context and Objectives: STABIWINE project objective is the development of alternative practices for protein and tartaric stabilization of wine, that are important phases of winemaking, particularly for wines exported and sold through organized distribution that undergo long traveling and long storing periods often in not totally controlled conditions. The stabilization technologies in use, albeit effective, have some negative side impacts on wine quality, production costs and environment, and for many decades the wine producers - in Europe and overseas - have looked for alternatives. A possible solution is offered by the use of biopolymers, i.e. compounds of natural origin, obtained from secondary products of the agro-food industry and already exploited in pharmaceutical and cosmetic sectors. The project is composed of two major activity pillars, one devoted to the development of a new processing aid for protein fining, and a second developing a new additive inhibiting the formation of tartrate precipitates in the bottle. Reticulated polymers for elimination of unstable proteins 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. Polyspartate to avoid tartrate precipitation Tartrate, an organic acid typical of grapes, combines with potassium and calcium, two cations highly present in grape and then in wine, thus originating crystals that precipitate in the bottle and form an unwelcome deposit for consumers: to avoid this phenomenon, before bottling most wines are treated in order to eliminate the excess of tartaric acid and/or potassium. According to the most popular technique, the wine is kept refrigerated to temperatures below 0°C for several days, thus inducing the formation and precipitation of crystals in the tank, which are finally eliminated by racking, centrifugation and filtration. This practice represents one of the most important point of energetic consumption in the winery, and has some negative effect on wine sensory profile. Furthermore, many small wineries cannot afford the purchase of the required equipment. The addition of metatartaric acid can represent an alternative to cold treatment, but limited to wines with short shelf life; other additives, such as carboxymethylcellulose (cellulose gum) and mannoproteins are effective only in wines with low instability, and are not allowed in the production of organic wines (increasing percentage of European wines). The same for electrodialysis and resin exchange, whose development in the wine industry is restraint by the high cost and by the related significant water consumption.
Stabiwine project intends to introduce in the wine industry the use of a new additive, able to inhibit the formation of tartrate crystal, thus preserving the original wine composition. The research is focused on polyaminoacids, and in particular on polyaspartate (PAA), a new anti-scaling additive that is seeing an exponential diffusion in other sectors thanks to their positive combination of efficacy, safety and pricing characteristics. Polyaspartate, obtained by polymerization - through simple heating - of aspartic acid, a widespread aminoacid; the compounds obtained has very high surface charge, and peculiar physical and chemical characteristics which makes it ideal for winemaking use.