1. Harvest Date
The moment the grapes are picked is a pretty big deal. It is probably the most important thing a winemaker can do to ensure that they make awesome wine. Picking earlier will produce wines with higher acidity, lower alcohol and perhaps more green flavors and aromas. It could also lend to morebitter tannin. Picking later in the harvest season will produce wines with lower acidity, higher alcohol (or sweetness) and more subdued tannin. Some wines when picked too late must be artificially acidified in order not to taste ‘flabby’ or ‘flat’. Additionally, some will have water added to them (called ‘watering back’) to reduce the alcohol concentration in the completed wine. This could be why many commercial wines have identical ABV levels of 13.5%.
Besides picking the grapes at the moment when acidity level and sweetness are perfectly in balance there’s also a weather problem. Every vintage is different. Sometimes weather takes a turn for the worse at the end of the growing season and can even result in a bad vintage. In a situation where rains are forecasted in cooler climate areas (Northern Italy, Burgundy, Oregon, etc) some winemakers may choose to hedge their bets and pick grapes before optimal ripeness.
2. Cold Soaking and Skin Contact
Winemakers often talk about maceration time (a.k.a. skin contact) and cold soaking. Both of these terms refer to how long the grape skins touch the juice while it turns into wine. Cold soaking is a process that happens before there’s alcohol in the mix. By keeping the grapes cold, the grape must is too cold for yeast to start fermenting. The theory of cold soaking is to carefully extract color and fruit flavors from the skins without extracting bitter tannin. The total time that grape skins touch a wine is maceration time.
For example, a Syrah producer called Kessler Haak in Santa Rita Hills , California macerates their wines for 50 days to extract the color and flavor. In comparison a few miles east in Santa Ynez, a Syrah producer called Solminer Wine Company macerates for just 28 days. The difference in color of the two wines is remarkable: one is very opaque and rich and the latter is pale and delicate like a Pinot Noir. Normal red wine fermentation generally takes around 2 weeks to complete.
You can understand skin contact by testing the differences in tea flavor by varying how long it sits in hot water.
3. Hot Fermentation vs. Cool Fermentation
Fermentation temperature is another technique that changes resulting fruit flavors and color in a wine. A hot fermentation can get up to 80-100 °F (26-37 °C — nearly hot tub temperature) as the yeasts metabolize and produce alcohol. Warmer fermentations are usually used for red wines for increased color and tannin. There are also several minimalist producers practicing warmer fermentation temperatures on white wines. Their goal is non-interventionist wine making that is more in tune with the conditions of the vintage.
Cold and cooler fermentations are usually practiced on white and rosé wines. Landon Sam Keirsey explained that cooler temperatures (from 42 – 50 °F, 6 – 10 °C ) help preserve delicate aromas in white wines. The reason for this is aroma compounds are volatile and are more likely to be lost at a higher temperature where reactions happen faster. This is probably why wine serving temperature greatly affects the taste of wine out of the bottle.
4. Pump Overs vs. Punch Downs
Pumpovers
Pumpovers can extract higher amounts of tannin in a wine depending on the frequency and force. Some pump over systems are basically wine sprinklers, offering a gentler extraction and some aggressively stir up the fermentation tank. For larger fermentation tanks in commercial operations, much needed oxygen comes through a pumpover device.
Punch Downs
Punch downs, on the other hand, are a very delicate way of stirring a wine. They keep skins from getting too extracted and little to no amount of added oxygen in the fermentation. Punch downs are typically done by hand and are more popular with non-interventionist winemaking.
5. Oak-Aging vs. Steel Tank
Oak aging does more than just add a vanilla flavor to wine. Oak increases a wine’s exposure to oxygen while it ages. Oxygen decreases tannin and can help a wine reach its optimal fruitiness. Wines aged for many years in oak develop nutty flavors. If you’re not that familiar with oak aging, definitely check out this article:
The Surprising Truth About Oaking Wine
Steel tanks are commonly used for zesty white wines like Pinot Gris, although it’s not uncommon to find steel tank aged red wines. Steel tanks limit the oxygen exposure to wine and keep wines fresher. You can learn more about how oxygen affects wine over time.
6. Corks vs. Screwcaps
One misunderstood topic about winemaking is the choice of using a cork or a screwcap. In most circumstances there is no difference between wine in a bottle with a cork or a screwcap. When asked what he preferred, winemaker, Landon Sam Keirsey said:
Personally if it was my decision I would use screwcaps.
The interesting thing about the topic of wine closures is that corks let oxygen in at unpredictable amounts. There is also an issue with TCA ‘cork taint’ that affects about 1-2% of wines. Screw caps (and other cork alternatives), on the other hand, can control the amount of oxygen that comes inside the bottle per year.