Posted on June 23, 2017
Have you ever uncorked an aged Bordeaux, and found a thick pile of sediment at the bottom of the bottle? Although this gritty sediment looks unappetizing, it’s actually a set of harmless compounds that play a major role in aged wines. The solid sediment in the wine mixes with the fermented juice over time, forming new flavor compounds that make the wine taste better with age. As these compounds expire, they sink to the bottom of the bottle.
Low wine turbidity makes the wine appear clearer, but it can also negatively impact its ability to age through the decades if it’s filtered too much. By comparison, wines with higher turbidity can sometimes age longer in a cellar, but they often appear unappetizing to casual drinkers. The winery’s goal is to find the ideal balance between these two factors, and many do so by measuring their wine turbidity in advance.
Wine Turbidity Varies by Style
Some winemakers prefer high turbidity in their wines, whereas others prefer there to be hardly any sediment at all. For instance, an organic, or “biodynamic,” winery will try to retain as much hazy turbidity as possible when they bottle their wines because they believe that interfering with the wine’s natural state will negatively impact its flavors. Consumers also expect a biodynamic wine1 to have some haziness and a significant amount of sediment since it’s a sign that the winery didn’t try to filter out the sediment before bottling. In some cases, high turbidity makes the wine appear more appetizing for certain customers, rather than less.
However, most wineries choose to filter out as much sediment as possible. A winery that wants their wines to appeal to mainstream, casual drinkers will want to make their wines appear crystal clear before bottling. An estimated 90 percent2 of all wine is consumed within its first year of purchase. Because these wines aren’t designed to age well over time, there’s no reason to have excess sediment in the bottle — the compounds won’t have enough time to expire and sink to the bottom of the container. This is why the majority of wineries choose to filter, or “fine,” their wines to create a liquid that is virtually clear.
Measuring Wine Turbidity Prevents Unexpected Expenses
You can’t tell how much sediment is in a wine just by looking at it. To start, the sediment is usually well mixed with the rest of the liquid, and it can take as long as 10 years3 for this hidden sediment to separate from the rest of the wine. Instead, wineries use a color and haze spectrophotometer to determine how clear the liquid is, according to Nephelometric Turbidity Unit (NTU) measurements. Knowing the wine’s NTU reading in advance allows wineries to estimate how many times the wine will have to go through a filter, and how much this process will cost. For instance, in most mainstream wines designed for immediate consumption, an NTU reading of less than 1.04 is considered relatively clear. However, if that reading were greater than 1.0, the winery would likely have to filter the wine for a second time before bottling.
If a winery uses a third party for filtering, as is often the case, that third party company might charge more for wines that have high turbidity. A thick, hazy wine can quickly block the filters on a machine, causing significant damage to the equipment. Many filtering companies won’t even accept wines that are cloudy. When wineries measure their wine’s turbidity in advance, they can take extra steps to clear out the wine before it reaches a third party filter company. Many wineries “fine” their wines with special agents5, such as volcanic clay, gelatin, and egg whites. These agents can grip onto large pieces of sediment to prepare the wine for further filtering. Knowing this in advance saves wineries hidden filtering fees, and prevents costly equipment damage.
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