#42: How Do We Know When To Pick Those Grapes? Part 2 of 2.
October 1, 2024
It’s important to keep good records of past harvest data. Why? All that information gives me some clue to the upcoming harvest dates, tonnage, sugars (Brix) and levels of acidity (pH). From averaging the past data, I can guesstimate the date that a specific block or a vineyard should be perfect for harvest and the date that chosen date will make a huge difference in the finished wine. Sounds easy, huh? It’s not. Even though I may have my carefully thought out “game plan” in place, it’s Mother Nature who dictates what she wants to do. I may have three aces in my hand of poker, but Mother Nature always seems to come up with her royal flush. Harvest never happens the way I thought it would.
By the time you are reading this we should be well into our 38th harvest. The box below, all based on the data from the past dozen years, were my projections of the picking dates, tonnages, desired sugars and levels of acid. (I’m positive the dates have changed since I wrote this…)
In order for me to evaluate the ripeness of the grapes that we will be harvesting using both the subjective (taste) and objective (hard numbers) we need to get an accurate sampling of those grapes. I begin about two weeks after the color of the grapes change (veraison) and will visit each site 3+/- times as we get closer to our “usual” harvest dates. This process of ripeness evaluation is called Berry Sensory Analysis (BSA). It may be very time consuming, but it’s the information I need to decide when to pick. Again, the date I choose to harvest those grapes will be all-important to the finished product.
Hopefully you read last month’s article on how to get a good grape sampling, the first step in BSA. Once all my marked baggies full of grapes are in the lab, I can begin the analysis, one block (baggie) at a time.
What exactly does Berry Sensory Analysis mean?
BSA is a technique to evaluate ripeness using a combination of both the subjective taste and the objective numbers using lab tools. (If the following is confusing, bring over a baggie of your freshly picked grapes and I’ll demonstrate.) Once the baggies with berries are in the lab, I will conduct the taste analysis before checking the Brix and pH numbers. (If I check those hard numbers first, they will influence my subjective evaluation).
The Subjective Part (Tasting)
Since the first part of BSA has to do with taste, it is best to not have just had a cuppa coffee (sorry) be sucking on a lemon drop (yum) or brushed your teeth (apologies to your spouse or dog….) prior to testing.
First, remove five “typical” berries from each baggie and place them on their own marked paper towel, one towel for each different baggie/block to be tested. Pop a berry in your mouth and squeeze it between your tongue and upper hard palate. Then pick out the seeds and put them on the paper towel and push the skins up into the corner of one cheek. Repeat with all five berries (no swallowing!) and you’ll end up with no seeds but all the juice and pulp in your mouth with the skins tucked into the corner of your cheek. Now you can begin to evaluate the four sensory parts of BSA and assign numbers (1, 2, 3, or 4) in each of the four below categories.
On your evaluation sheet, write down the date, variety and vineyard site. Next evaluate and assign a 1, 2, 3 or 4 number to the pulp and juice in your mouth: is it acidic (1) or is it sweet (4)? Secondly is the pulp and juice herbaceous (1) or fruity (4)? Write those numbers down and spit out the pulp and juice (if you swallow all day, you’ll get a tummy-ache, trust me….). The third evaluation is to chew the skins that were tucked up in your cheek fifteen times: are they hard and herbaceous (1) or fruity (4)? After writing down that number, spit out the chewed skins and perform the final subjective analysis: the maturity of the seeds. Take one brown or black seed from the paper towel, chew it and assign a number: is it herbaceous and bitter (1) or does it taste like toasted almonds (4)?
Once all four subjective tests have been done and numbers 1-4 have been assigned, I check the objective, hard-number data.
The Objective Part (Lab Tools)
As best you can, squish all the berries in the baggie. Now separate the juice in your baggie from the seeds and squashed skins. It takes a little practice and I do it by opening a small exit at the corner of the Zip Lock and squeeze the liquid into a small beaker. (A strainer tends to clog up with the pulp.) You may have to repeat the process a couple of times (it takes a little practice) but you’ll end up with only the juice (and some pulp) in the beaker. Now it’s time to check the juice in the beaker and get the Brix and pH numbers using your refractometer and pH Meter. (Be sure to read the directions for each tool prior to using….)
Brix Using the Refractometer:
Stir the juice in the beaker well and place a drop or two on the glass of your refractometer. A reading will show the Brix (sugar) level. Write down that number.
pH Using the pH Meter:
After standardizing the pH electrode (read the directions) stir that same juice in the beaker again with the electrode, wait for the reading and write down the pH number next to the Brix data.
What Happens Then?
Once you have both the subjective and objective numbers, the next step is to compare that data with all the BSA information from prior years. Now I can attempt to guesstimate the number of days it will be until that block of grapes will be perfect to harvest. I’ll then check the upcoming weather (possibility of rain or excessive heat?) and finally check for crew availability. Now our “perfect” harvest date will be set. It’s still a guessing game, but I have concrete data to back up my decision.
Simple, huh? Yikes!
Here’s to a good harvest!
“Great wine requires a mad man to grow the vine, a wise man to watch over it, a lucid poet to make it, and a lover to drink it.”
Salvador Dali
-Squire Fridell