Winemaking at Morrisons
"Wine is magic. The fact that something as disarmingly humble as fermented grape juice can give me as much pleasure as the most complex, passionately performed music, can take me on journeys as illuminating as any trek into the wilderness..." Max Allen.
Good wine is something to savour and enjoy but good wine can only be made from quality fruit.
The vigneron's first major task is to have the grapes at the desired degree of ripeness ready for harvesting. This takes nine months of hard work with the assistance of suitable climatic conditions.
Grapes contain between 10-20% sugar and 5-10% acid. Grapes from cooler areas tend to have more flavour than those from warmer zones. From shortly after veraison it is important to monitor the development of the fruit to select the right time to harvest.
The right time to pick grapes is based on four criteria:
- sugar content
- pH level
- titratable acidity
Taste is the most important indicator to selecting the correct time to harvest. The winemaker should know the style he wishes to make and the flavour indicators for that style. Stalks and seeds should have lost their green colour.
If the fruit is not ripe don't pick it, we don't eat fruit that is not ripe.
Red Wine Making
- Pick grapes, test for sugar content, pH, titratable acidity and taste
- Crush, destem grapes or stomp on them
- Crush the grapes early in the morning when they are cool, since the lower temperature reduces the risk of bacterial spoilage and oxidation of the juice.
- Prepare the yeast using grape juice
The winemaker needs to determine which yeast indicators to use:
- General purpose strain - usually strong fermenters
- Style oriented strains - yeasts linked to grape variety and wine style
- Fermentation specific strains - adds to wine quality features
- Tolerance to high alcohol
- Tolerance to variations in temperature
- Wild or natural
Add nutrients to stimulate yeast activity and assist the ferment
- Plunge the cap regularly, 6 times per day
- The cap of skins which forms a layer on top of the fermenting juice must be moistened with fermenting juice a minimum of six times each day.
- Leaving the cap heightens the possibility of acetic acid forming which can lead to volatile acid levels and wine spoilage.
- Cover the open vats with sheets to protect the ferment from vinegar flies. Temperature and Baumé monitoring should be carried out twice daily.
- Check if second application of nutrient is required to prevent H2S
Fermentation can take 5 days to 4 weeks depending on:
- Volume of the juice
- Fermenting temperature
- Yeast strain
- Nutrient available to the yeast strain
- Solids content of the juice
Towards the end of the fermentation the rate of conversion of sugar to alcohol and Carbon Dioxide decreases resulting in a decrease in the production of Carbon Dioxide. To assist in determining if the ferment has finished the following processes can be carried out.
Using a hydrometer test the specific gravity of the wine. As an approximate guide, a specific gravity reading of 0.95 will indicate that fermentation has finished. Testing for residual sugar should be carried out to avoid fizzy wine.
Pressing the skins
The fermenting juice is then pressed and the fermenting juice is placed in tanks or barrels. Only light pressing is recommended, resist the temptation to press hard to extract every litre of juice possible. The risk of extracted phenolic characters being transferred to the wine, resulting in greenish, unripe and bitter characters through hard pressing is too high.
The wine is then transferred to barrels to mature.
Most red wines should undergo a malolactic fermentation. The conversion of malic acid to lactic acid allows the wine to become more mellow to taste. Test for the completion of the MLF fermentation. As soon as malo has finished additions of sulphur (40ppm) should be made to protect the wine.
Rack wine off into another container and place in an oak barrel after three months.