Marquette (red wine) Grapes
HARVEST PARAMETERS. We have lots of grapes schedule to arrive this weekend at Train Wreck Winery. We will be harvesting our own Marquette, and we will be getting Frontenac and Frontenac Gris grapes from several growers.
How do we know when the grapes are ready to harvest? Science and experience. In a perfect world, there would arrive a moment when the sugar and acids were in just the right amounts. That seldom happens. So we pull sample clusters from the vineyard, trying to get a representative mix of clusters. Clusters that are exposed to the sun will ripen faster than those that may be shaded.
We press the juice out of this sample, and test for pH, sugar %(called “brix”) and sometimes other things such as titratable acidity(TA) or yeast assimilable nitrogen (YAN). Because of variablilities of rain, sun and growing degree days, the numbers we measure in the lab are seldom exactly what we are aiming for. And even though our lab tests might dictate waiting, we may see degradation in the quality of the grapes in the vineyard, or maybe we have to pick this weekend because next week is the big game and nobody will want to help pick. So we pick when the science, our experience, and our gut tells us the time is right.
Steve has been busy in the cellar and around the state over the past week. Here are his notes from this period. Enjoy!
FERMENTATION. On Friday Aug 29th we inspected the juice. Very little activity is present. This is due to the temp of the juice. Going from the freezer, thru the destemmer, and thru the press, the resulting juice was in the low 40’s. By Thursday it had raised to 52 degrees. Today it is 56 degrees, so the juice is still a little chilly for our yeast, for which the optimal temp is 59-65 degrees. We’re keeping the facility chilly (60 degrees) to encourage this slow warm up. We want a slow, cool fermentation to encourage the properties we want in the finished wine.
We now have Brianna, Edelweiss and St Pepin juice fermenting in the winery. We are monitoring the Brix in the wine to make sure the fermentation is going smoothly. Once about a third of the sugar has been converted to alcohol, we add nutrients to the fermenter. The product we use is Fermaid-K. This product provides yeast nutrients, particularly nitrogen, to the yeast cells to ensure they don’t stress from lack of essential foods. Other stressers include high alcohol and heat. We treat the latter by keeping the volumes low and the winery cool. As we’re shooting for an alcohol level of 11%, the fermentation should be complete before high alcohol becomes a problem.
This year many growers are reporting sour rot in their Brianna grapes. Unlike other fungi that we prevent by proactive means, sour rot occurs when grapes are damaged. The skin on grapes can be broken by any number of things: insects; hail; cracks caused by drought/too much rain; birds. Once the skin is compromised, sour rot sets in. At that point there is little to be done except to sort the clusters at harvest and get the grapes processed as quickly as possible. The main concern is the amount of Volatile Acidity (VA) in the juice/wine. VA is basically vinegar, and can cause flavor issues. There is a federal limit of 1.2 grams/liter of VA. So I sent juice samples off to the Iowa Grape and Wine Industry Institute for testing, and our VA is well within the limits.
Snuck away from a function at the Depot last night and added Fermaid-K to two tanks of Brianna. The sugar had reached about 2/3 its original amount. Fermentation additions have to be done at certain points of the process, and cannot be delayed.
Checking the ferms this morning for temperature and any off-odors that may have developed. We’re off to a wedding in the Quad Cities this evening, so won’t be able to check them again until noon on Saturday. I think we may be getting grapes in tomorrow, too.
Welcome to our Winemaker Blog. Train Wreck Winery winemaker, Steve Larson, will share the experiences of growing and harvesting grapes, and the process of making wines. Please follow along, ask questions, and if you enjoy the story, please share with your friends!
BRIANNA HARVEST. We picked our Brianna grapes on Saturday August 23d. The timing of harvest is based on the chemistry of the grape, as well as when we can get help to harvest. In the grape, we’re looking at sugar levels, pH, and total acidity.
For the Brianna, I focus on the sugar level (expressed in degree Brix). Brix is actually a measure of dissolved solids, but virtually 100% of dissolved solids in grapes consists of sugar in the form of sucrose. For Brianna grapes, we’re looking for 15-17 Brix. If the sugar gets higher, this grape can develop aromas we don’t want. “Foxiness” is a term used for one of those aromas that we don’t want. Some use the term “cat-pee” instead of foxiness. Either way, sounds like something we want to avoid.
We’d like the pH of the grapes to be 3.2 if possible; our grape juice ended up at pH 3.05, with a Brix of 15.5. So we liked the sugar level, and can deal with the low pH. We harvested about 4,500 pounds from our half acre of Brianna, which is double our yield from last year. This yield resulted from a better-than-usual fruit set at bloom, and our intentional leaving of more buds at pruning this spring.
Because of mechanical difficulties with our destemmer, we brought the grapes to the winery and put them in our walk-in freezer at 28 degrees. The cold temp, along with the judicious addition of sulfite, keeps the berries fresh until processing.