As we finish up the stabilization steps for our 2021 wines and prepare to bottle them this spring, we’re thinking ahead to sweetening them a little bit to help balance their tart acidity. In order to figure out the best sweetness level to use, we set up a bench trial. Like all bench trials, the goal was to try a range of different addition rates. In this case, we evaluated the results using our sensory perceptions; in other cases, such as determining how much bentonite is needed for protein stability, lab analysis is also required.
The first step in planning any bench trial is to be familiar with the material you’ll be adding. This is especially true for additives where the active ingredient is only a percentage of the material’s total composition, such as potassium sorbate where sorbic acid accounts for 74.7% of the mass. In the case of bentonite trials, a 6% slurry is commonly used. For our sweetening trial, we made a 50% sugar solution that would be easier to mix into the wine samples than trying to get solid sugar crystals to dissolve.
Based on your goals
For the wine, you’ll need to determine the range of addition rates you want to try. For our 2021 La Crescent and 2021 Rosé wines, we didn’t want them to be overly sugary, but we did want to bring the acid into balance with some sweetness. So we tried adding 0.5%, 1%, 1.5%, 2%, 2.5%, and 3% sucrose (table sugar). Just to be sure, we also compared these to 4% and 5% sucrose additions. For other materials, such as fining agents, the supplier will often provide a range of recommended addition rates.
It can take a while for some additives to achieve the desired effect or to settle out of the wine before evaluating it, so any waiting period should be planned ahead, too. This means gassing the headspace of the sample containers to prevent oxidation and storing them at cellar temperature. The samples may then need to be filtered or gently decanted off the sediment before tasting or analyzing in the lab.
Then comes the math.
For our sweetening trial, we had eight different sugar addition rates we wanted to try, plus we also included a non-sweetened control for comparison, making a lineup of nine samples. We had two people tasting, and wanted to give them each 40mL of wine per sample. We multiplied (9 samples) * (2 people) * (40mL) = 720mL. So we collected our base wine in a 750mL bottle.
In order to calculate how much sugar solution to add to each sample, first we had to recall that we were using a 50% sugar solution, and that we were making 80mL of sample (to split into two 40mL tastes). Knowing these things, we used the formula C1V1 = C2V2 to determine how much sugar solution to add to the 80mL of wine. In this equation,
- C1 = the concentration of our sugar solution = 50%
- C2 = the desired sugar addition rate in our wine sample = 0.5%
- V2 = the volume of our wine sample = 80mL
So we ended up with (50%)*(V1) = (0.5%)*(80mL), and we found that V1 = 0.8mL of our sugar solution. We then repeated this calculation for the other addition rates. A spreadsheet can also help with these calculations, particularly for making quick adjustments to the number of people tasting or the tasting volume they’ll be given.
While the details will vary depending on your needs, the basic process of conducting bench trials is the same. Be sure to know the material you’re working with, consult the supplier’s guidelines, and plan ahead. If you have any questions about setting up bench trials, please reach out to us at firstname.lastname@example.org.