TECHNICAL FIELD

The present invention concerns a method for preparing preservatives in the wine industry.

BACKGROUND ART

As is known, wines require the addition of chemical substances to prevent their deterioration due to the action of micro organisms or oxidisation by the oxygen contained in the air. Said chemical substances are generally indicated as preservatives.

Few preservatives are truly harmless. The majority of preservatives can have undesired effects if certain consumption limits are exceeded. These food preservatives include the sulphites commonly used in the wine industry.

For a correct evaluation of the toxicity of said preservatives it is important to remember that, for example, sulphites, which are often added in the form of sulphurous anhydride (S0 ₂ ) , can trigger allergies in sensitive persons which manifest themselves in breathing problems, while in the case of non-sensitive persons, they are nevertheless toxic if consumed in large quantities.

In the wine industry, the need for preservatives that are effective in preventing deterioration of the food and at the same time are free from toxicological contraindications is therefore widely felt.

The Applicant has devised a method for producing preservatives for wines based on extracts and molecules from appropriate plant species so as to replace the molecules produced by chemical synthesis like the sulphites, for example, currently widely used in the wine industry. DISCLOSURE OF INVENTION

The subject of the present invention is a method for preparing preservatives in the wine industry comprising in an operating sequence the following steps:

- extraction in which a plant species with antioxidant and antimicrobial properties is subject to an extraction process to obtain a phytoextract mixture;

- separation in which the phytoextract mixture resulting from the extraction step is subject to a separation process in order to separate said phytoextracts as a function of their molecular mass;

- mixing in which a light portion of phytoextracts obtained from the separation step and a heavy portion of phytoextracts obtained from the separation step are mixed together with the addition of water.

Preferably, during said extraction step said plant species with antioxidant and antimicrobial properties is subject to a flow of sub-critical carbon dioxide.

Preferably, in said extraction step the sub-critical carbon dioxide is used at a temperature ranging from 20 to 30°C and at a pressure ranging from 50 to 75 atm.

Preferably, in said separation step the phytoextract mixture resulting from the extraction step is subject to chromatographic extraction by means of the action of sub- critical carbon dioxide .

Preferably, in said separation step the sub-critical carbon dioxide is used at a temperature ranging from 20 to 40°C and at a pressure ranging from 40 to 70 atm. Preferably, in said mixing step bi-distilled water is used at a temperature ranging from 11 to 30°C, a pH ranging from 7 to 7.5 and a redox potential ranging from 100 mV to 200 mV.

Preferably, the plant species used comprises one or more of the following compounds: Vitis Vinifera Sativa, Pisum Sativum, Acacia Arabica, Acer Campestre, Actinidia Chinensis, Alpinia Galanga, Anemone Epatica, Arbutus Unedo, Artemisia, Atriplex Orthensis, Beta Vulgaris, Borago Officinalis, Carum Copticum, Caria Illinoensis, Alchemilla Alpina, Polygonum Cuspidatum, Triticum Vulgaris.

Preferably, in the mixing step a fraction of the phytoextract portion with molecular mass ranging from 7000 to 20000 Dalton obtained from the separation step and a fraction of the phytoextract portion with molecular mass ranging from 100 to 1000 Dalton obtained from the separation step are mixed with each other.

A further subject of the present invention is a preservative for use in the wine industry.

A further subject of the present invention is a wine comprising a preservative as defined above in the amount of 0.1 to 2.0 ^' ml per litre of wine. BEST MODE FOR CARRYING OUT THE INVENTION

For a better understanding of the present invention, an implementation example is given below for illustrative non- limiting purposes. PREPARATION OF PRESERVATIVE FOR WINES

- Primary extraction with sub-critical carbon dioxide - An extraction apparatus comprises an extraction unit and a precipitation unit. The extraction unit comprises, in turn, a rectangular-shaped receptacle made of stainless steel, in which the plant material is subjected to a flow of sub- critical carbon dioxide at constant temperature of 25 °C and pressure of 68 atm for a period of 5 minutes; the plant species consists of 100 g of grape seeds of Vitis Vinifera with a piece size of 2 mm, 50 g of pods of Pisum Sativum with a piece size of 5 mm and 50 g of grains of Triticum Vulgaris with a piece size of 3 mm. After a period of equilibrium, the saturated solution is passed into the precipitation unit through an expansion device, for example a capillary nozzle, where it remains for 2 minutes . Once the primary extraction has been completed, the exhausted plant raw material is eliminated, while the liquid portion consisting of phytoextract is collected ready for the next separation step. - Chromatographic separation with sub-critical fluid -

Dense gas phase carbon dioxide at a temperature of 30°C and a pressure of 71 atm is used as the sub-critical fluid.

A separation column is filled with zeolite having a diameter of 1 mm. In particular, the separation column is divided into an extraction portion and a discharge portion.

The separation is performed by means of a temperature gradient. The extraction portion is provided with a heating system by temperature gradient throughout its height, with temperatures ranging from 15 to 30°C and increasing with height .

In the extraction portion the phytoextract mixture to be separated and sub-critical carbon dioxide react for a period of 5 minutes at a temperature ranging from 15 to 30°C allowing solubilisation of the compounds to be fractionated; in the following adjacent discharge portion, the mixture of phytoextracts and sub-critical carbon dioxide react for a period of 3 minutes at a temperature ranging from 5 to 10°C so as to drastically reduce the solubility of one or more compounds; the portions of phytoextract are collected from the different sectors of the discharge section as a function of their molecular mass (the pressure necessary for the extraction increases with the molecular weight of the compounds, by volatility (the compounds with higher vapour pressure are more soluble) and polarity (for example in an apolar sub-critical fluid like C02 the solubilisation of apolar compounds is favoured) ) thus identifying them as "light" portions, for the compounds having a molecular mass ranging from 100 to 1000 Dalton, and "heavy" portions, for the compounds having a molecular mass ranging from 7000 to 20000 Dalton, which will be subsequently mixed with one another after appropriate selection. - Mixing -

100 ml of phytoextracts of the "light" portion obtained from the separation step and comprising compounds with a molecular mass ranging from 100 to 1000 Dalton and 50 ml of phytoextracts of the "heavy" portion obtained from the separation step and comprising compounds with a molecular mass ranging from 7000 to 20000 Dalton are mixed with 850 ml of bi- distilled water at a temperature of 10 °C and having a pH of 7 and a redox potential of 100 mV until complete homogenisation. One litre of the resulting solution has the following composition: 850 ml water; 3 ml arabinose, 25 ml apigenin; 3 ml ampelotin; 35 ml cyanidin; 5 ml peonidin; 3 ml malvidin; 30 ml anthocyanin; 35 ml procyanidins ; 3 ml eugenol; 2 ml phytosterols , 2 ml betanin, 2 ml theophylline, 2 ml thymol.

- Test on wine preserving power -

The resulting solution was tested as a preservative for wines.

In particular, 0.5 ml of solution per 1000 ml of wine were used. For comparison, sulphurous anhydride was used as a traditional preservative in a quantity of 40 g per 1000 ml of the same wine .

After 220 days, a sample of 250 ml of each of the two wines was analysed to verify the presence of the compounds listed in Table I and considered the main indicators of correct vinification.

Table I shows the values in mg/litre of the above-mentioned compounds both for the wine treated with the preservative obtained by the method of the present invention (Inv. wine) and for the wine treated with sulphurous anhydride (Comp. wine) .

TABLE I

The compounds listed in Table I are roughly indicative of the positive trend of the fermentations that govern vinification such as, in particular, alcoholic fermentation and malolactic fermentation; the parameters of the comparison wine (obtained with the traditional method) show a normal fermentation process with the normal use of sulphurous anhydride in the quantities described. The wine produced with the innovative preservative shows a substantial similarity with the comparison wine as regards the shikimic acid parameters (index of antioxidant quality of the wine) and tartaric acid parameters (index of freshness and liveliness of the wine) , while-, it ^* shows a drastic reduction in the levels of sulphurous anhydride and an improvement in the malic acid and lactic acid parameter. The reduction in the levels of sulphurous anhydride shows that it is possible to eliminate it completely without compromising the other parameters; on the contrary, they are improved. As can be seen from the experimental data of Table I, use of the preservatives according to the present invention not only avoids the use of potentially toxic preservatives, but at the same time guarantees quality improvements in the wine .