Modern Trends in Winemaking

Objectives of the course

Student gets knowledge about new techniques, already used in the wine making technology, the suitability of their use regarding the wine quality and their influence on the wine character.

Prerequisites

Knowledge of mathematics.

Assessment methods

Written and oral assignments.

Course contents

Lectures

White wine

The white wine technology is now going in to two different directions:

1. The increase of sort character - especially of the grape sort aroma,
2. The increase of extractability and stability of white wines (the maturing of wine on the lees or addition of the died yeast cells during the wine maturation).

The increase of white wine sort character

Monoterpens (sort aroma carriers) are found in the grape berry skin and in the grape mould. They are synthetisised only 7-10 days before the full grape ripeness. The mission of the technology is to preserve or increase the extraction of these compounds from the berry skin as much as possible. This can be reached with:

• Short term cold maceration of de-stemmed white grapes mesh (under 10°C, 6-12 hours). Terpens are bonded to the pectin and sugars with ester bonds. The addition of the pectolitic enzymes with ß-glucosidasic activity is possible to release the bonded pectin or the use of specially selected yeasts (the yeasts aroma) which contain this enzyme. This is how the aroma carriers are released during the alcoholic fermentation.
• Longer contact between the berry skin and must can be achieved in the process, where 2-3 % of mature berries are added during the fermentation and than removed with the first racking of the wine. Wines, produced by the technology, described previously have extremely expressed sort bouquet, but because of lower fermentation temperatures (below 15 °C) posses less extract. The use of enzymes is recommends for the wines that are consumed in one to two years from the production, especially for the aromatic wines (sauvignon, muškat).

The increase of white wines' extractability

Extractability can be increased by alcoholic fermentation under higher temperatures (above 20°C), where more glycerol is produced, as well as higher amounts of higher alcohols (heavy flavor). Because of much intense fermentation and CO2 formation soft bouquet can be lost and higher alcohols formed during the fermentation can cover the sort character. Some people in wine trade business say that hiperoxidation of the white must is the best solution, where already pressed must is oxygen aerated. Added oxygen enhances the bonding of polyphenols with the proteins. The clarification of the musts is quicker, higher aeration enables faster multiplication of the yeasts and consequently larger amounts of glycerol is produced. Addition supply of the oxygen can cause the monoterpenes' oxidation-which are known as sort aroma carriers. This procedure makes such wines richer in taste (good maturation) with less expressed sort bouquet. More recently, especially in the southern Slovenia wine growing parts (in Brda and Koper region) is for wines, rich in alcohol (above 13 % v/v alcohol), recommended wine maturation in wooden barrels on the lees (or in stainless steel tanks with periodical ventilation with oxygen) and stirring the lees. Addition of already dead yeast cells is possible. Such maturation is going on for 6 ore more months, by stirring the lees 2-3 times per week. Malolactic fermentation happens at this kind of wine maturation (the transformation of malic acid to lactic acid), from the dead yeast cells (added or in the lees) yeast proteins are extracted - manoproteins. They are composed from the amino acids and sugar part-glucose and mannose. The main role of manoproteins is:

• Wine aroma bonding - preserving for longer period,
• Stabilization of the tartrates crystallization (a substitute for the metatartaric acid)
• They prevent the protein haze - by bonding the termo-labile proteins (lesser needs for the bentonite).

Red wines

Carbon maceration:

• Short-term maceration for young wines such as Beaujolais type,
• Long term maceration for red wine aging,
• Prolonged classic maceration.

Short term carbon maceration of the whole clusters, or only partly stemmed grapes (1/3) is performed in closed high-pressure tanks with 1-1,5 bar of up-pressure. Released CO2 during the alcohol fermentation is regulated with the pressure reducing valve. Alcoholic fermentation is performed in the berries. Due to hard living conditions, the yeasts are now forming more fruity higher alcohols, fatty acids and their esters. Short-term maceration lasts for 2-3 days. The color compounds are extracted in those period-only anthocyanins but not other phenols. Such young wines have intense ruby color tens, fruity bouquets, velvety, a bit tannin and due to CO2, fresh.

Long-term carbon maceration can last even for 14 days or more. After 4-5 days, are also tannins (beside anthocyanins) extracted from skins and seeds. Such wines are rich in fermentation aroma (heavy aromas from higher alcohols), chewy and prepared for at least 2-3 years aging. In that period, the tannins are than condensated, become insoluble, therefore less tasted and softer.

Prolonged classical maceration, even to one month is performed at 25-30°C, with "punching down the cap". After the alcoholic fermentation, when the "cap" of skins is resuspended, the post maceration is going on, a week or 2, just to finish malolactic fermentation. These wines preserve more sort character, are rich in extract and very good for further maturation and aging.

Integrated wine making

Like in grape growing, there are some limitations also in the integrated wine making processes, which lower the use of means, which are bad for human health and also environment and also lower the environment pollution and exploitation. Alternative technologies will be presented, regulations, book keeping of the tracebility, labeling and marketing of integrate made wine.

Field observations

The visit of highly sophisticated and modern wine cellar is planned and see practical performance of some new technological procedures. One world known wine exhibition will be visited, where some new things, which are implemented in the wine technology will be presented. (ENOVITIS).

Recommended reading

• Kropivšek, D. s soavtorji. 2002. Pravilnik o integrirani pridelavi grozdja in vina in tehnološka navodila za integrirano pridelavo grozdja za leto 2003, 35 p
• Dodatna študijska literatura bo povzeta in na voljo iz strokovnih revij in znanstvenih člankov