The Backyard Vineyard – Determining Ripeness

Of all your decisions for a backyard vineyard, one of the most important is choosing your harvest date. No matter how well you pruned the year prior, how good your soil may be, or how well you trained your vines the first year, if you don’t time your harvest according to ideal ripeness, you won’t make a good wine.

In some parts of the world, such as The Republic of Georgia, there are indeed some grandfathers who’ve been making wine so long that they are able to walk through the vineyard in September, taste a few grapes, and determine that it is time to harvest based on flavor. This is certainly standard for us to strive for and a Grand-Dad Duty skill set that could pay off in the long term.

However, for those of us starting off in the backyard vineyard wine business, it is best to stick with the numbers.

In short, all you need to know is your Brix and your pH.

Calculating Your Brix

You can determine your Brix in two ways: with a hydrometer, or with a refractometer. While using a hydrometer is more accurate, you’ll be crushing quite a large number of grapes in the weeks prior to harvest in order to get a stable reading. This is meaningless when you are working hundreds of acres, but this makes us cringe in our backyard vineyard operation so we stick with a refractometer.

All you need to measure Brix with a refractometer are ten grapes or less and a strainer. Simply walk through the vineyard, choosing grapes from the center of the clusters, and selecting clusters from multiple vines and rows as you go in order to get a randomized sample of the entire vineyard. Focus on those grape clusters which are most uniform in color/maturity, and consider “dropping” those which are not (i.e. cutting them down so as to allow the vine to focus on developing those clusters you’ll actually be harvesting).

Once you’ve got two handfuls of grapes to work with, head to your kitchen and crush the grapes into a wire strainer, ensuring only clear, strained juice enters whatever vessel you’ve chosen to capture the juice (we just use a wine glass, so that we can drink the juice once we’re done measuring it.)

With a good amount of juice to work with, simply take out the siphon/baster included with your kit, siphon a few drops of liquid, and place three drops carefully onto the refractometer reading glass. Then, carefully fold the plastic top onto the reading pane, allowing the three drops to spead evenly along the reading pane with a uniform layer of juice.

At this point, all you need to do is point the refractometer in the direction of sunlight and look through the dial as if it were a pair of binoculars. The Brix level will be clearly displayed. Break out your winemaker journal, jot down the reading, and move on to pH.

Calculating Your pH

With the same set of juice in your glass (don’t drink it just yet – you still need to measure your pH), you can now break out your handy pH meter and determine your pH. Once your pH meter is properly calibrated (instructions generally included with each purchase/model), simply place the tip of the meter into the grape juice and allow the digital reading to stabilize. Repeat this process 2-3 times to ensure accuracy. Record your pH and move on.

Doing Your Math

With your Brix and pH determined, all you need to do now is crunch a few numbers. The most simple and consistent formula we’ve found for the backyard vineyard enthusiast is Brix x pH².

First, square your pH by multiplying it by itself. In other words, if your pH is 3.1, multiply 3.1 x 3.1. Then, multiply this product by the Brix. For white wines, you’ll want to harvest when this number gets as close as possible to 200. For red wines, you’ll want to harvest when this number gets as close as possible to 260.

For example:

White Grapes/White Wine
pH: 3.3
Brix: 20
Formula: Brix x pH²
Calculation: 20 x (3.3 x 3.3) = 217.80
Aiming for: 200
Analysis: this is pretty close to your 200 target. If the number is creeping up week after week, moving farther and farther from your 200 target, harvest immediately.

Red Grapes/Red Wine

pH: 3.5

Brix: 19

Formula: Brix x pH².

Calculation: 19 x (3.5 x 3.5) = 232.75

Aiming For: 260

Analysis: this is also a solid reading and pretty close to the 260 ideal. Never allow the pH to go higher than 3.5, though, as you’ll risk spoilage of the entire batch (wine needs acidity at 3.5 or below to naturally fight off spoilage organisms).

Considering the Weather

In addition to watching the birds, bees, hornets, and deer (each of these species will be attracted to the veraison and sugar content of your grapes) during harvest season, you’ll want to watch the weather.

As you calculate and track your numbers, watch out for drenching rain storms in the forecast as well. Rain just before harvest can swell the grapes, causing them to prematurely crack and burst in addition to overall just diluting the peak veraison flavors with excess amounts of water. These bursts also invite pests to attack the vineyard, as well as allowing spoilage microorganisms to begin developing.

Bottom Line: if your numbers are decent and you have a lot of rain coming, harvest immediately to avoid the trouble described above.

Final Thoughts

Let us be clear – it is nearly impossible to align your pH and Brix with ideal weather and a drop in local pests in addition to coordinating your harvest schedule with your spouse, kids, friends, and that early September family beach vacation.

At the end of the day, if you can align two or three of these factors with everything else going on in your life, you’ll be in good shape.

Harvest is less about the perfect product and more about enjoying the process.  We hope your juice is as good as the squeeze.

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Terminology

Veraison

Veraison is the fancy French word for the end-of-season ripening process. It specifically relates to the change of color in the grapes, particularly the reddening of unripe green grapes in the late summer and early fall. This is a beautiful time of year in the vineyard, but be aware that you (humans) are not the only ones who notice the changing colors!

Brix

Also known as degrees Balling, Brix is just a fancy term used to describe the percentage of sugar found in the grape juice. When sugar is present in a liquid, it raises the “specific gravity” above 1.000, which is the specific gravity of distilled water. Using a hydrometer, or a handy refractometer, you can quickly determine sugar content by measuring the official Brix every few days during peak veraison.

pH

For those of us who did not pay attention in high school, pH is the number of free hydrogen ions (H+) in a solution. More practically speaking, it measures how acidic your wine may be, as nearly all pH measurements in harvest season will read below 7 (neutral), which falls on the acidic spectrum of the 0-14 pH table. Ideal pH for red grape juice is 3.4, and 3.1/3.2 for white grape juice.

Titratable Acidity

We are listing this term here simply so you are aware that it exists, but we generally don’t measure it because it is incredibly complicated, difficult to standardize, and we’ve made perfectly drinkable wine simply by focusing on pH and Brix. In short, though, acids give wine the crisp, thirst-quenching qualities of a good wine while also protecting against spoilage. Titratable acidity (TA) is a measure of total acid in grape juice as expressed through tartaric acid content.