Introduction. 3. Antioxidant action, as free sulphur dioxide can reproduce some phenolic oxidized forms of must and wine in reduced form.

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1 EXPERIMENTAL PRODUCTION OF WHITE SPARKLING WINE WITH NO SULFITES ADDED Istituto Professionale di Stato Giuseppe Medici Legnago, Verona, Italy Anno Scolastico 2014/2015

2 Introduction Sulfites are additives largely used in food in order to increase the preservation of the products. They are steadily used in wine production. Sulfur dioxide presents: 1. Antimicrobial action, as it deactivates the enzymes which control the cell life of bacteria (0.8 mg/l of SO 2 ) while only 2 mg/l are needed in order to inhibit Saccharomyces cerevisiae 2. Antioxidasic action, as the sulphur dioxide in its free form can link itself to the polyphenol oxidase enzyme inhibiting it 3. Antioxidant action, as free sulphur dioxide can reproduce some phenolic oxidized forms of must and wine in reduced form. The European Community has decided the maximum limits of SO 2 in wine: 160 mg/l for red wine; 210 mg/l for white wine; 185 mg/l for sparkling wine. Anyway, the use of SO 2 must be limited to the bare minimum as it causes the same cellular alterations in human beings as it does in microorganisms. 2

3 Introduction During the alcoholic fermentation, yeast produces sulfur dioxide as metabolic intermediary, so different quantities of sulfites are naturally produced in each kind of wine. The dosage of sulfites in a glass of wine is generally tolerated by most people, but an increasing number of people show allergies and other health issues after the ingestion of these substances. Considering the increasing request in wine market of white wines with no sulfites and considering that wine is a probiotic beverage, if drunk in adequate quantities, we have started an experimental production of white sparkling wine with no sulfites added. In this way we can demonstrate the feasibility of the process and the creation of a product with a high quality standard. By removing the sulphur dioxide from the production process we have made a product which can satisfy the new needs of consumers, in this way the product can be drunk also by people allergic to this chemical substance. 3

4 Materials and methods The grapes used for the winemaking process have been cultivated in a small estate owned by our school. This estate is located in Fondo Pietà Legnago (VR) nearby the school itself (about 200 mt). For the vinification process we have used 340 kg of grapes: 90% trebbiano; 5% chardonnay; 5% malvasia. 4

5 Materials and methods 18 kg of the best grapes have been let wither in a cool and airy room. That in order to obtain afterwards the must which will be used as sugar mixture for the fermentation in bottles. For what concerns the fermentation process we have used Saccharomyces cerevisiae yeasts chosen for white wines. For what concerns the fermentation in bottles we have used Saccharomyces cerevisiae yeasst chosen for fermentation. 5

6 Materials and methods In order to calculate the sugar degree we have used the Babo densimeter. The procedure has been developed by William Babo, the degree is usually referred to a temperature of Babo=10 gr sugar in 1000 gr must. The total amount of acid has been calculated through titration of 7,5 ml of must, using bromothymol blue and sodium hydroxide 0,1 N. In order to calculate ph and temperature we have used a Milwaukee ph meter. 6

7 Materials and methods The grape harvest has been handmade. We have used a stemmer crusher, then we have pressed the stemmer through a vertical wine press. The fermentation process took place in glass carboys. The mashing of the withered grapes has been handmade, then the new fermentation process took place in glass bottles with crown taps. The bottles have been under a constant remuage. The final alcohol degree has been calculated through Malligand ebulliometer. 7

8 Process We have decided to harvest the grapes for the experimental vinification when the samples analyzed in the school chemistry laboratory had reached: Babo; g/l total acidity; ph In the last decade of September we harvested the grapes in the first hours in the morning ( ). The best grapes ( about 18 kg) has been let wither at a temperature of 17 C with a U:R: of 70%. The remaining grapes have been destemmed, pressed and then pressed again in a vertical winepress. The must obtained from the pressing has been transferred into a stainless steel tank for a couple of hours in order to obtain a prefermentative clarification. 8

9 Process After the clarification pause, the must has been transferred in glass tanks. Now the fermentation yeasts have been prepared (20 g/hl). They have been regenerated with the addition of physiological water at 38 in relation to 1:10 and with the addition of 5gr sucrose. After 30 minutes 2 l must have been added. After two hours the content has been added in the must contained in the tanks and during the following 24 hours the fermentation process has started. During this phase the process temperatures have stabilized at about C. After 8 days the turbulent phase of fermentation has come to an end. After this phase we have proceeded with the racking, in which we have divided the 150 l of wine in: 2 tanks of 54 l 1 tank of 20 l 1 tank of 15 l 9

10 Process After 7 days we have made the first decantation, in order not to keep the wine with the sedimentation lees. In this way we have obtained: 2 tanks of 54 l 1 tank of 20 l Afterwards, at regular intervals of 14 days we have made two decantations and we have obtained: 2 tanks of 54 l of wine After 60 days the withered grapes showed 25 Babo and a loss of weight of 35%. We have proceeded with the handmade mashing and in this way we have obtained 3 l must. After that we have bottled 54 l of wine as still meal wine, while the remaining 54 l have gone under the process of a new fermentation in bottles. 10

11 Process We have added 18 g/l of sugar cane to the 54 l of wine meant to become sparkling (each 4 g/l we obtain a bar). In this way we have granted the necessary sugar to the yeasts for a new fermentation. We have added 5 g of Saccharomyces cerevisiae selected for the fermentation process to the 3 l must obtained with the withered grapes. Now the must has been mixed with the 54 l of basic sparkling wine. The content has been bottled in high pressure proof glass bottles with crown caps. Then we have transferred the bottles in the cellar at a temperature of 12 C. After 3-4 days the CO 2 production has started and we could check the process of the new fermentation. At intervals of 15 days we have made the remuage in order to avoid that the dead yeasts and some lees at the bottom of the bottles could crust. 11

12 Process After 30 days from the bottling of the basic sparkling wine we have done the racking. Before this operation, the bottles have been turned upside down and put in the freezer at a temperature of -15 C. That s has been done to obtain the tartaric stabilization of the wine and to let the lees deposit near the neck of the bottles, so that, when uncorked, the pressure in the bottle could quickly eject the lees and limit the waste of the product. 12

13 Process The racking has been handmade turning the bottles upside down and uncorking them in a container filled with cold water. In this way the pressure generated by the wine quickly ejects the lees which had settled in the neck of the bottles. Moreover the waste of the product is reduced. At this stage of the process we have calculated the alcohol concentration of the sparkling wine through Malligand ebulliometer. We have recorded a value of 11.5% of ethyl alcohol compared to the volume of the product. 13

14 Process After the racking we have filled each bottle and corked them again with a crown cap. Then we have put the previously prepared labels on the bottles. Once the process has ended we have sold the bottles and we have noticed a remarkable approval by the buyers. We have preserved some sparkling wine in order to evaluate the quality features of the product and the stability of the wine in time. As we have already said, we haven t added during the process. Anyway, a small part of it (about 15 mg/l) has self-produced during the fermentative process of the yeasts. 14

15 Conclusions The use of previously withered grapes used to start the fermentative process was a technique already used in the past, but it was abandoned because of the high production cost. Nowadays some wineries are developing and improving this technique in order to increase the value of their products. Considering the increasing attention showed by the allergic consumers about the products contained in the wine and considering the increasing number of consumers allergic to sulphur dioxide, we could demonstrate that it is possible to produce white wine with no sulfites added. The few self-produced sulfites of the fermentative process avoid the presence of oxidative phenomena and the quality standard of the product is kept high. Anyway, it is important to start from a raw material as much as possible healthy, because avoiding the use of sulfites makes it difficult to manage the alterative microorganisms. Moreover, avoiding the use of sulphur dioxide the wine is more linked to its region because the autochthonous yeasts naturally present in the cuticle play a role in the fermentative process and they affect the process itself. Through this work the students attending the last three years have been involved in every production stage giving them the possibility to live all of these stages; in this way they have acquired the production technology in order to exploit the products of their region. 15

16 Bibliografia Barrajón N., Arévalo-Villena M., Rodríguez-Aragón L.J., Briones A., Ecological study of wine yeast inoculated vats from La Mancha region. Food Control, 20, Boulton R.B., Singleton V.L., Bisson L.F., Kunkee R.E., Principles and Practices of Wine Making. Chapman Hall, New York, 604. Delfini C., Scienza e tecnica di microbiologia enologica. Ed. Il lievito., Asti. Ferreira J., Du Toit M., Du Toit W.J., The effects of cooper and high sugar concentrations on growth and fermentation efficency and volatile acidity production of different commercial wine yeast strains. Australian Journal of Grape and Wine Research, 12, Mercado, L., Dalcero, A., Masuelli, R., Combina, M., Diversity of Saccharomyces strains on grapesand winery surfaces: analysis of their contribution to fermentative flora of Malbec wine from Mendoza (Argentina) during two consecutive years. Food Microbiology., 24, Sciancalepore V., Industrie Agrarie, UTET, Italia. Vezzosi C., Tecniche agroalimentari, Edagricole, Italia. 16