Four Parts of the Grape and What They Contain
Pulp: Water containing sugar, tartaric and malic acids.
Skins: Flavor compounds, tannins.
Pips & Stems: Tannins, but pips have bitter oils.
Bloom: The waxy surface covering skins, contains yeasts.
Three Phases of Grape Processing
Grape Reception: First does of S02, grapes sorted.
Destemming and Crushing: Optional. Crushing breaks skins and liberates free run juice, but crushed pips release bitter oils.
Pressing: Separates the liquid and solid and solid parts of the grape. For white wines, before fermentation, for roses and reds, skin contact is allowed.
Changing Sugar Levels in Winemaking
Must enrichment is the winemaking adjustment that occurs when there is not enough sugar in the grapes, so sugar is added. This then allows the wine to have more alcohol if before fermentation. Can make the wine boozy and thin-tasting.
Changing Acid Levels in Winemaking
Deacidifcation can happen by adding potassium bicarbonate, or a mix of calcium carbonate and calcium tartrate-marlate.
Acid levels can be increased by adding tartaric acid in powdered form.
Changing Tannin Levels in Winemaking
Tannin levels can be raised by
adding tannin powder, stems or wooden staves to the fermentation vat.
Or, some of the juice can be removed to make a rose.
Too much tannin is handled by avoiding too much extraction.
Temperature Control during Alcoholic Fermentation
Alcoholic Fermentation is the conversion of Sugar to Alcohol and CO2 by Yeast, with other byproducts are heat and flavor compounds. It starts at 5C and will stop if it runs out of nutrients, sugar, SO2 is added, or hits 15% ABV. Temperature management is important -- low temps avoids the loss of delicate fruit aromas, high temps develop more savoury aromas and increase extraction.
Wild Yeast vs Cultivated Yeast Strains
Ambient yeasts were traditionally used, but now winemakers control them with S02 and introduce cultivated yeasts to control the outcome of fermentation.
Malolactic Fermentation (MLF)
Happens after alcoholic fermentation and is completed by lactic bacteria. Converts tart malic acids into softer lactic acids. MLF softens and reduces acidity, creates hazlenut and butter flavors. Some fruit flavors are lost and the rounder, richer wines are less refreshing.
Red Wine Making Process
Crush (must to make rose)
Cold Maceration (add sugars or tannins)
IF FREE RUN, then MLF to New Made Wine
If SKINS AND LEES, Press, Press Wine, MLF, Press Wine
Optional for winemakers to let the grapes macerate at a low temp before fermentation starts. Increases extraction of color and flavor aromas. Can also do this at higher temps, but this can reduce fruit aromas.