Let's dive into the frosty world of cooler white wine fermentation. The temperature at which you ferment your white wine is not just a minor detail. In this article, we will investigate what happens when you ferment at lower temperatures, detail some easy home winemaking techniques, and discuss commercial yeasts that are suited for the task at hand. During the colder months, you might be able to easily try some of these techniques at home.

Overview:

Why the cold, you ask? When you ferment white wine at colder temperatures, typically between 45-60°F (7-15°C), you're essentially slowing down the yeast's metabolism. This is akin to putting the yeast on a slow, scenic train ride rather than a high-speed express.

This leisurely pace allows the yeast to retain more esters, the compounds responsible for the stone fruit and floral aromas that are characteristic of cold fermented whites and make your nostrils dance with delight. At higher temperatures, more of them bubble out. Think of them as the secondary violins of your orchestra, providing those high, sweet notes that make your wine's melody that much more memorable and complex.

Moreover, fermenting at lower temperatures also inhibits the production of fusel alcohol, which in reds is an advantage but not so with whites. In a white wine, you want your alcohol to be almost exclusively ethanol. As long as your temps stay below 68 degrees, fusel alcohol will not be produced. The fusel alcohol present in reds fermented at higher temps is balanced out by tannins and oak. Whites have no tannins and oak is often limited to Chardonnay. It has characteristics that favor oak infusion, however, it is an exception, not a rule. Any white will never be as bold as a Cabernet Sauvignon or Zinfandel, so oak and fusel alcohol should not be invited to the fermentation party. Think of whites and reds as personality types. Big reds are extroverts and whites are introverts.

Techniques:

Now, how can you, the home winemaker, achieve these cooler fermentation temperatures? It's simpler than you might think. You don't need a frosty cave or a high-tech refrigeration system. A cool basement or porch, a temperature-controlled fridge, or even a tub filled with ice water can do the trick. Try using a container that is larger than your fermenter and make the equivalent of a double boiler.

It is also advantageous to ferment in smaller batches and in vessels that have snap lids with airlocks. It is easier to control the internal temperatures with smaller volume. If your temps start to kick up, you will have an easier time dropping the temperature of 6 gallons of must than 50. If you don’t have this option and are fermenting in steel tanks, another trick is to freeze water bottles. Just sanitize them and drop them into your must. Small bottles are better especially if you are working with smaller batches because they give you more control.

Conversely, if you are taking advantage of winter temperatures, you might need to employ techniques to keep your wine warmer for which you can use a brew belt. It wraps around your fermenter and will help keep your wine in the right temperature range if your fermenter is in a cold porch or basement. As long as you have a means to monitor temperatures, you have an array of options at your disposal. 

With these colder temps, it is important to not rack the wine too soon. By doing so, you decrease the yeast population which you need especially at the end of fermentation. Once you get to those higher alcohol levels, yeast slow down dramatically. So you need large populations to finish the job. Cold fermentation can take as long as a month to 6 weeks to complete.The ability to keep the fermenter closed towards the end is critical as the wine becomes more vulnerable to oxidation at the later stages of fermentation as it produces less CO2.

Remember, your goal is to keep the yeast cool and comfortable, not frozen. It's a delicate balance.Too cold, and the yeast may go dormant and stop fermenting. Too warm, and you risk rushing the fermentation and missing out on those delightful esters.

This process might seem labor-intensive and for a few days, it will require attention to detail. However, the temperature is most critical during the peak fermentation phase. This is when the yeast is most active. As the fermentation progresses and the sugar levels decrease, the yeast activity naturally slows down and is less prone to warming. At this point, the temperature becomes less of an issue. However, it's still important to avoid any drastic temperature changes that could shock the yeast and potentially halt fermentation prematurely.

As the alcohol levels increase, the yeast becomes more tolerant to higher temperatures. But remember, a slow and steady fermentation at a consistent, cooler temperature is key to developing those desirable complex flavors and aromas in your white wine.

So, while the temperature control might seem less critical as fermentation winds down, it's still important to maintain a relatively cool and stable environment for your yeast to complete its job. What will make this easier is that as fermentation progresses, it is easy to maintain the cooler temps. Activity ultimately decreases producing less heat. That said, you will still want to monitor your internal fermentation temps and adjust accordingly.

Yeasts: There are several commercial white wine yeasts that are engineered to perform optimally in the cooler temperature range of 45-60°F (7-15°C). Here are a few examples:

1. Lalvin ICV D47: This yeast strain is known for its ability to produce full-bodied, complex whites with good structure and fruit concentration. It performs well at temperatures as low as 50°F (10°C) but can still function with temps as low as 45!

2. Lalvin QA23: This yeast is known for enhancing freshness and fruit character in whites, and it can ferment at temperatures as low as 50°F (10°C).

Remember, each yeast strain has its own unique characteristics and will contribute differently to the final wine. It's important to choose a yeast that complements the grape variety and style of wine you're aiming to produce. If you are working with wine kits, most come with EC-1118 which can ferment as low as 50°F. 

So, embrace the chill of cold fermentation and let your white wine sing with all the fruity and floral notes it can muster. By employing these easy hacks and with some extra attention, you can make your whites taste and smell how they should. Remember, in the world of white wine making, cool is definitely the new hot!