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Carl Hudson
January 20, 2021 | Carl Hudson

Bench Trials for Winemaking - 2021

Since being involved in winemaking and wine evaluation efforts for well over 20 years, it seems that the subject of wine bench trials should have come up sooner.  Bench trials represent an important part of the winemaking process, and even though they require a lot of thought, preparation, and record-keeping, they are typically fun and exciting.  This edition of Carl’s Corner will address some key reasons winemakers do bench trials, including:  blending for flavor adjustment (acidity, alcohol, tannin), sweetening, fining to remove solids and cloudiness, and treatments to enhance cold and heat stability.  Each of these specific topics is briefly discussed below.  While doing bench trials, it is best to involve some other interested folks, take notes, and discuss the effects.  The goal of bench trials is to determine the least intrusive treatment that will yield the best possible wine.

Conducting bench trials is an ordered process in which samples of the original wine(s) are collected and measured, then divided into separate containers which are used in making blends or adjustments.  For example, if a Merlot wine needs a bit of extra tannin on the finish to be well-balanced, blending with a fairly tannic wine like Petit Verdot or Petite Sirah might be a good choice.  There are also tannin additives that can be used.  So, several samples of Merlot will be prepared to which various amounts of the blending grape wine and/or additive will be added, mixed, and then tasted for evaluation.  Of course, keeping good records on what is done at each step is very important.  Typically, there is no right answer, but the winemaker will be the final judge of success. 

We see a lot of blended wines in Texas.  In fact, most red wines from around the world are blends.  Often bench trials are done with different grape varieties or cuvées of the same variety, to find the blend that best expresses the aromas, flavors, and structure that a winemaker prefers.  These are often the most fun bench trials, and can involve a number of people, associates, fellow workers, consultants, and even interested friends.  For more on blending, see a previous Carl’s Corner – Blended Wines in Texas, 02-Aug-2017.

Often bench trials are done to help balance the acidity and alcohol levels in a wine.  A wine that is too acidic will be tart and somewhat unpleasant, while a low acid wine may be too bland and uninteresting.  Blending different wines can address this issue, or certain adjustments can be made with selected additives to moderate the acidity level.  The percentage of alcohol in a wine can also create an imbalance, either too high or too low.  Again, blending different wines is a common way to adjust alcohol level.  For example, a common practice in warm weather regions is to blend Viognier that can reach very high sugar levels (therefore high alcohol) when fully ripened, with earlier-picked fruit having less sugar content, or with a grape variety (e.g., Semillon) that ripens at lower sugar content.  This is done to produce a lovely, balanced white wine with an alcohol level that is NOT too high (say 15-16% ABV down to 14-14.5% ABV).  For more on blending, see previous Carl’s Corners – Flavor Adjustments For Wine, 26-Sep-2018, and Acidity in Wine – Part 2 in the Winery, 16-Jan-2020.

Sweetening wines almost always requires bench trials to get the right amount of sugar (or grape juice concentrate) addition to develop the desired flavor profile.  The sweetening process requires a balance between the sweetening agent and other characteristics of the wine – acidity, alcohol, and tannin structure.  This concept of sweetening wines was addressed in Sweetening Wines, 6-Jan-2021. 

Often it is necessary to introduce additives to a wine in order to remove flocculent solids and cloudiness that either will not settle or precipitate out in a timely manner, or ever.  The most common additive to accomplish this fining process is an activated, food-grade clay called Bentonite.  Bench trials are important to determine the minimum amount of bentonite needed to clarify the wine so to not remove more color and flavor compounds from a wine than is necessary.  This process of fining and clarification was discussed in Dirt Can Make Wine Better, 17-July-2019. 

Treatments to enhance cold and heat stability are usually required to make a wine stable during storage, shipment, and time on the sales shelf or in the cellar.  The above mentioned bentonite can be important as it attaches to and helps remove protein materials from a wine that can, over time and under warm conditions, coagulate and create cloudiness.  Again, bench trials are important to determine the minimum amount of bentonite required to render a wine clear and clean under a specified set of test conditions. 

Cold stability is also a concern as the natural product, potassium bitartrate (what most of us know as Cream of Tartar), can and will precipitate from a wine under cold conditions.  This precipitate, often called wine diamonds, is harmless, but sure can look ugly.  So, bench trials are important to determine how best to cold stabilize a wine.  One method involves chilling a cuvée of wine to a temperature less than would be expected during shipping, storage, or refrigeration for a period long enough to precipitate excess potassium bitartrate (typically 24-28 deg F for 6-12 days).  Unfortunately, refrigeration equipment is always costly, and this procedure is time consuming.  There are additives available that attach to potassium bitartrate and keep it in solution so it does not precipitate when chilled.  If using these additives, bench trials are really critical to determine just the right amount necessary. 

As consumers, we typically do not have to worry about, or even think about doing bench trials.  All we need do is step up to the bench (tasting room counter or a table) and enjoy wines that Texas winemakers have already taken through any necessary bench trials. 


This edition of Carl’s Corner was prompted by a very informative article, primarily focused on home winemakers:  Performing Bench Trials, by Bob Peak, WineMakerMag.com. 


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