Brix, PH, Titratable acidity – things to do in the lab before harvest
View over the vineyards to the Marmara Sea.
I am currently spending some time working at the Chateau Kalpak in Turkey where we wait for the harvest to start any minute. While waiting we enjoy the nice view out of our window but cannot help asking ourselves: What goes on in the lab down in the cellar and what implications does it have for the harvest? And, above all, for the wine?
I join Sevgi Tuzel, the assistant wine maker, and become the assistant’s assistant for a little while. Having no clue of chemistry myself, I will try to understand the processes involved and try to explain them to you in simple words. I hope you enjoy this and maybe you learn something new, too. I for myself learned a lot! So, let’s get started!
Sqeezing Merlot for further analysis.
We take a few grapes from each variety (Merlot, Cabernet Sauvignon, Cabernet Franc, Petite Verdot) and sqeeze some juice into different glasses. We label them so that we don’t get the varieties mixed up. The juice is what we will be working with in the next couple of hours determining brix degrees, the pH level and the amount of titratable acid. No need to panic yet by the sight of these words, take a deep breath, relax. I will explain.
Cabernet Sauvignon, Petite Verdot and Merlot waiting to be analysed.
Degrees Brix
What is it?
Degrees Brix is the measuring unit for the sugar content in liquids, mostly juices. It is used in most of the English speaking countries. In Germany, Austria and Switzerland the measurement degrees Oechsle is used to measure the sugar content. Knowing how much sugar the juice contains is important because it gives you an idea how much alcohol can be produced in the wine if all sugar is fermented. To get the number of the estimated alcohol content you have to multiply the degrees Brix by 0,55. Usually degrees Brix between 20 and 28 are considered good for wine making. In our analysis, the degrees Brix were around 23 to 24.
How do you measure it?
A refractometer is used to measure the amount of sugar in the juice. You place a drop of juice on the glass at the front of the refractometer and look through it. You can see the degree number on a scale inside the refractometer.
Me using a refractometer. Very exciting.
Why is it important in relation to wine?
It is important to know the sugar content of the grape juice in order to know how much alcohol will be in the wine. If you want a wine with a higher alcohol content then you wait until the degrees Brix is a little higher. For example: you want a wine with 12% of alcohol, then you should harvest your grapes when the degrees Brix are 21,8. Would you like your wine to have 14% alcohol content, then you have to wait until the Brix reaches 25,5 (always multiplied by 0,55 as mentioned before).
Titratable acidity
What is it?
Wine consists of different acids, with the tartaric acid (German: Weinsäure) being the most important one. Another acid in wine is the alic acid (German: Apfelsäure). The titratable acidity (TA) measures the amount of the tartaric acid that is in the grape.
How do you measure it?
We take a glass, fille it with destilled water, add an alkalic solution, namely Sodium Hydroxide (alcalic solution neutralizes acid), then add the juice and use an indicator to indicate the change in colour of the grape juice. When the pH level reaches a certain number, namely 8,2, we calculated the TA value. I cannot remember how this number was calculated. But as with the degrees Brix you want a certain range in number that indicates the desired level of acidity.
Filling in the Sodium Hydroxide.
Why is it important in relation to wine?
A good balance between acidity and sugar is your main goal in wine making. So when the sugar levels go up, as happens in the ripening period, acidity levels go down. Acidity is importat in giving the wine some structure, so you don’t want acidity levels to fall down too much. If acidity is too low, then wine tastes flat and boring. You want some sharpness in your wine, you want to taste it. Ans the TA give this sharp taste to the wine.
Sevgi testing the acidity.
Ph level
What is it?
The pH level is a measurement for acid and alkali in liquids. It shows the degree of acidity in the grape juice or later in the wine. That means it tells you how sour the liquid is. Water has got a pH level of seven and is therefore neutral. Numbers under seven indicate a sour liquid, numbers above seven indicate a more alcalic liquid. The lower the pH level, the higher the acidity. Or, the lower the acidity, the higher the pH level. Got it? Usually, the pH level of wine is around 3 to 4.
How do you measure it?
We are using a pH meter to determine the pH level. It’s a electronic device that you put into the glass filled with juice. You twirl the juice around a bit while a glass stick is held into the juice. The glass stick transmitts the pH level to the electric device and you can read the number in the display.
Testing the pH level with a pH meter.
Why is it important in relation to wine?
When the grapes ripen, the sugar content rises, the acid level falls and the pH level rises accordingly. Since pH level is all about the concentration of acid in the liquid, we want the acid levels to be high enough and the pH level low enough so that the wine doesn’t become flat. Acidity in the wine gives the wine structure and freshness and also helps deter some wine faults. So, when the pH level is at a desired level, harvest can start. The levels vary from red wine to white wine.
All three parameters, degrees Brix, Titratable Acidity and pH level are taken into account to determine the ripeness of the grape and thus to determine the perfect moment to start harvesting. The last two are both used to determine the acid content in wine. The difference being, as far as I understand: pH tells you how much acid is in the wine, whereas the TA gives you an idea how strog this acid might taste. For each wine maker this moment may come at a different stage with different values of these three indicators, depending on the style of wine the wine maker wants to make.
What happens to all the nice juice that we analyse? Well, see for yourself.
There goes the juice.
Thank you Sevgi Tuzel for showing me the workings of a wine laboratory. I had a great time and really appreciate it!
There goes the juice.
I hope you enjoyed reading this. I tried my best to capture this challenging topic. If you have something to add or to correct, please let me know!