Alphabet Soup of Wine

You may have noticed that some wineries provide technical sheets for their wines. These sheets often contain a bunch of acronyms - pH, TA, RS, and ABV. Ever wonder what they mean and whether you should care? Let’s demystify this alphabet soup of wine.

Alphabet Soup by Sigmund on Unsplash

pH 

pH stands for potential of hydrogen or power of hydrogen. It measures the acidity or alkilinity of an aqueous solution. The pH scale ranges from 1 to 14, with 7 being neutral. Wine is acidic, and its pH usually runs in the 3’s. White wines pH is typically in the 3.0 to 3.6 range, and red wines in the 3.4 to 3.9 range. Wines with lower pH tend to be more puckering on the palate, while wines with higher pH tend to be rounder. Think lemon juice versus tomato juice.

pH Scale by Alvy16 on WiKimedia Commons

In the vineyard, pH is used in conjunction with TA (or Titratable Acidity), sugar, and flavor to determine the optimal time for harvest. pH in grapes increases as they ripen and further rises incrementally during the fermentation process. If pH is lower than 3.0, it may be an indication that the grapes have been harvested before they are fully ripened. The resulting wine flavor may not be well developed. The reverse is true if pH is more than 4, suggesting a flabby wine with little acidity to liven it. 

Fun Fact: Acidity acts as a buffer to preserve wine. Wine collectors often favor a vintage with a lower pH for cellaring.

TA

TA is often used to refer to Total Acidity and Titratable Acidity interchangeably. The truth is that Total Acidity is the measure of both titratable and non-titratable acids. However, because Titratable Acidity is easier to derive, it is often used as an approximation of Total Acidity. In this blog post, TA refers to Titratable Acidity. A good TA range for white wines is 7-9 g/L and that for red wines is 6-8 g/L. 

While pH measures the intensity of acids, TA measures the concentration of acids. To illustrate the difference between pH and TA, let’s make a Bloody Mary.

 

Bloody Mary by Toni Osmundson on Unsplash

1. Mix 0.5 oz of lemon juice to 2 oz of vodka and taste it. It will likely pucker you up! 

2. To that, add 4 oz of tomato juice, mix, and taste again. It will taste less sour. 

Both lemon juice and tomato juice are acidic ingredients. However, lemon juice contains citric acid which has a low pH of 2, while tomato juice contains a blend of citric, malic, and ascorbic acids with a combined pH of 4.1 to 4.4. So even though the concentration of acids (or TA) in the drink has increased with the addition of the tomato juice, the intensity of the combined acids has decreased.

 3. Now add your Worcestershire sauce, Tobasco sauce, horseradish, celery salt, and all the other good stuff and enjoy!

Fun Fact: While some wine collectors use pH as an indication of good acidity and therefore aging potential, others use TA as a measure. A vintage with a higher TA is definitely preferred for aging to a vintage with lower TA. 

RS

RS stands for residual sugar, the leftover grape sugar after alcoholic fermentation is completed. RS is measured using g/L or %. (10 g/L is 1% residual sugar.) Most dry wines will have close to zero residual sugar so you don’t typically see RS listed in the tech sheet. Sweet wine starts at about 35 g/L or 3.5% RS and can go up to over 200 g/L or 20% RS. 

Sauternes by Jeff Burrows on Unsplash

Some of the best sweet wines are produced as a result of botrytis, also known as Noble Rot. Botrytis is a type of fungus that causes grapes to shrivel. As water content evaporates from the grapes, the sugar level increases and intensifies. This causes alcoholic fermentation to complete with excess sugar remaining. Famous botrytized wines include French Sauternes, Hungarian Tokaji, and German Beerenauslese or Trockenbeerenauslese.

Fun Fact: The most expensive botrytized wine is the Royal Tokaji Essencia that at one point cost $40,000 a bottle. The last I checked, you can get a half bottle for about $1,000.

ABV

Last but not least, ABV stands for Alcohol by Volume. It measures how much alcohol is in 100 mL of wine and uses % as the unit of measure. ABV of a wine is dependent on the grape sugar pre-fermentation. During alcoholic fermentation, wine yeast converts grape sugar into ethanol. Wine grapes or vitis vinifera often reach 22 to 26 degrees Brix (symbol °Bx) by harvest. 1 °Bx is 1 g of sugar in 100 g of crushed grape juice and will yield about 0.55% in alcohol content. 22 to 26 °Bx will yield about 12.1 to 14.3% ABV.

Measuring Brix

While most new world wines tend to run high in ABV, some European wines have less than 10% ABV. Moscato d’Asti runs around 5-6% ABV, and German Riesling runs around 7-8% ABV. By law, these old world wines are required to stop fermentation before all the sugars are converted to alcohol to create the respective styles of sweet wines.

Fun Fact: In the United States, the alcohol excise tax for wine above 16% ABV is about 50% higher than that for wine at 16% ABV and below. For that reason, you will not see many bottles of wine (if any!) with ABV above 16%.

I hope you enjoy the demystifying of the alphabet soup of wine and gain some confidence in reading wine technical sheets. And if you are hoping to start a wine cellar, you are now armed with a bit more knowledge on how to pick wines with aging potential. Salud!

First Vintage

Last October I posted about my first winemaking experience; well at least from crush through the primary fermentation and press. That was probably the most involved part of winemaking, when twice to thrice-daily punchdowns took place with constant measuring of temperature and Brix. That was when the juice was transformed from 'must' to wine as sugar got fermented into alcohol and carbon dioxide.

Secondary Fermentation

After the press, we moved into secondary fermentation of the wine in air-locked vessels. We used a 5-gallon glass carboy and three gallon jugs to use for top-up (I'll get into that later). This period was generally uneventful and less involved, but there were a few things that required attention.

Controlling the temperature. Malolactic (ML) bacteria, which was added to the juice the day before press, were quietly converting tart-tasting malic acids into fuller-bodied lactic acids. ML bacteria are sensitive to numerous factors (e.g. pH, SO2, and alcohol levels), but the one thing that worried me was my ability to keep the wine within the optimal temperature range (>70 degrees). The carboy and gallon jugs were wrapped in blankets, snugged in cardboard boxes, and gently warmed by a heating pad. My biggest fear was stuck fermentation since there were no easy tests to perform at home or measurements to track progress. I resorted mostly to prayers.

Lees left behind from racking

Racking, racking, racking. Even though most of the solid remains of the grapes and yeast (also known as pomace or marc) were removed during the press, there were still some remaining in the wine as it went through secondary fermentation. These are called the lees. Decomposing yeast in wine could cause off flavors. In order to remove the lees, we did multiple racking of the wine during secondary fermentation. Racking is the process of siphoning wine off of dead yeast into new containers.

We siphoned a total of four times; the first time was 24 hours after press, the next two were a week apart, and the final one was a month out.

Racking also has two other advantages:

• It clarifies the wine. You could literally see that the juice got clearer after each racking. In many cases, clear wine is just a matter of aesthetic. If the wine tastes good, cloudiness may not indicate flaws.
• When done correctly, racking can introduce controlled amount of oxygen into the wine. During the early part of secondary fermentation, oxygen has positive effects on unfinished wine by stabilizing the color and tannins. It allows the wine to mature gracefully and become more complex. In the later part of the secondary fermentation, caution is needed to minimize oxygen contact. If acetic bacteria is exposed to wine and oxygen, it will turn the juice into vinegar (acetic acid). 

It is important to note that you will lose wine during racking due to spills and as you avoid siphoning lees. The loss of wine during racking may increase the air space between your wine and the airlocks. You can top up the carboy with wine from the jugs or similar store-bought wine (preferably same varietal and AVA). Alternatively, you can add sterilized marbles into your containers to raise the wine level. I personally put some of my top-up wine into a sanitized plastic container, squeezed out as much air as possible, and capped it. It worked!

Final Testing

After more than three months of secondary fermentation, we performed the final testing of our wine to check on sugar, acidity, and ML fermentation. During the primary fermentation, which lasted less than two weeks, I was constantly monitoring and measuring progress. For the much longer secondary fermentation, I really had no idea what to expect. But I was pleasantly surprised by the outcome.

• Residual sugar was at 0.3%. This was probably the least of my concern since we pressed the wine at a really low Brix. Residual sugar over 0.6% is a concern for still red wine as it may cause re-fermentation in the bottle.

Measuring residual sugar in the wine

• pH was 3.78. This was slightly higher (or less acidic) since harvest, which was at 3.53. But it was still within the normal range.
• Titratable acidity (TA) was 7.3125. TA measures the amount of total acids and was higher than our reading during harvest, which was 7.125. It was a bit higher than I like, but not bad.
• ML fermentation appeared to have completed. While not the most accurate way to test the concentration of malic acid, the chromatography test is cost-effective. The solvent used for the chromatography is extremely toxic, and the test takes several hours. After putting dots of wine sample onto a piece of chromatography paper, it was left in a big glass jar with the solvent and the lid closed tight. 

With one exception, most of the wines appeared to have completed ML fermentation. Yellow patches indicated presence of acids. The top row of yellow revealed the presence of lactic acid, which is the goal of the ML fermentation. The bottom row of yellow revealed the presence of tartaric acid, which is also what we expected. Any yellow in the middle role revealed the presence of malic acid, which would indicate that ML fermentation has not completed. This would show that the wine has not stabilized and will need more time for ML fermentation to complete.

Chromatography test revealed that one of the wines still had malic acid

Bottling

Once the wines had passed all the tests, they were ready to be bottled. We got the bottles that we have saved up, cleaned, and sanitized. (We recycled bottles. If you buy new bottles, you can skip the above steps.) Sulfites were added to the wine just before bottling. Sulfites are a preservative and will keep the wine fresh. They are also anti-oxidants and will protect the wine from oxidation.

Adding sulfites to wine

Siphoning wine into bottles

Corking wine bottles

Finally, five months after harvest and crush, our first vintage was bottled and proudly named Abscession - a joke, as my husband was recovering from an abscess the day of the harvest. Special kudos go to my partner-in-wine, Alisa. That's her work on the label, making an access look classy. The wine will officially be released in the summer, so check back later.

Abscession 2016 Syrah

My Verdict: I am having so much fun learning about winemaking. It gave me a greater appreciation for wine. I don't think going commercial is my calling, but I'm planning for my next vintage already! 

First Crush

It was a breathtaking drive from Seattle to Snoqualmie that sun-soaked September afternoon. I was exhausted and a bit cranky, having to juggle work and taking care of a sick husband and an injured dog.

However, mother nature had chosen the harvest date, and then we were given but a few days notice to get ready for the crush. I left my invalid family members in the good hands of our house guest, packed the primary fermenter, towels, and rubber boots into the Forester, and headed out to the crush facility. My excitement grew as I approached the facility - my first crush!

Crush Day

Our Syrah grapes were picked earlier that day from Chandler Reach Vineyards, technically considered to be in the Yakima Valley, but within close proximity of the Red Mountain AVA. My partner-in-wine, Alisa, and I decided to share 100 lbs of grapes between us, which would make us about two cases of wine.

At the crush facility, the winemaking class instructor, Steve, showed us how to set up the crusher and de-stemmer. All equipment were rinsed appropriately before we proceeded. Working in a group, we gently dropped bunches of grapes into the machine, which quite efficiently removed the stems and lightly crushed the grapes into the primary fermenter. But just in case, there were two of us who manually picked out stems that were missed by the machine.

There was a certain rhythm to crushing grapes that relaxed me. It was almost therapeutic! This was the first crush for most of us, and we were eager to learn and to help. As we got the hang of it, we moved faster through the bins of grapes. Our sticky grape stains were evidence of our achievement that day.

Gently dropping grapes in

Crushed and de-stemmed

More stems manually removed

Must in primary fermenter

The freshly crushed grapes, also known as must, smelled terrific. Sulfite was added to remove any wild yeast and bacteria from the must. After crushing nearly a ton of grapes (literally) and cleaning up all the equipment, it was time to take some measurements before we took the must home.

• Brix, which measures the sugar content of the must, was at 26 degrees. It was higher than the desired range of 22-25. A higher than desired Brix might lead to high alcohol content before fermentation could complete. This could result in a stuck fermentation.
• pH, which measures acidity, was at 3.53 and was within the desired range of 3.5 and 3.8.
• Titratable acidity (TA), which measures the amount of all the combined acids in the must, was at 7.125g/L and was slightly higher than the desired 4-6g/L.

The adjustment to the must needed was thankfully simple enough. To correct the Brix without adversely impacting the pH and TA, we diluted the must with water with precise measurements that Steve provided.

Alisa, my partner-in-wine, and I with our must

Primary Fermentation

A full day after the crush, we introduced re-hydrated yeast into the must and proceeded with the twice to thrice-daily punch downs. Punching down is a process to keep the juice and the crushed grapes, particularly the skins, in contact during primary fermentation. As must ferments, the crushed grapes tend to rise to the top forming what is known as the cap. Pushing the cap down into the juice allows for flavor extraction and also prevents unwanted bacterial activities.

A pack of nutrients were added to the must two days later to feed the yeast, and a second pack was added after another two days. The must was bubbling happily and got hot (around 75 to 80 deg F) with yeast activities. Unfortunately, I never got to the desired temperature range of 80 to 90 deg F. But the house smelled like a winery during primary fermentation so I took that as a good sign!

Yeast hydrated in must and warm water

Must bubbling during fermentation

In less than a week after the crush, the Brix had dropped to 6 degrees. Twice-daily punch downs continued, and four days later, the Brix measured at -1 degree. The must was then inoculated with malolactic (ML) bacteria as we prepared for the press the next day. The ML fermentation process allowed for a controlled conversion of the tart-tasting malic acids to softer lactic acids, which would hopefully enhance the body and flavor of the wine.

Press Day

To prepare for the press, all equipment needed to be sanitized. It was not the most interesting part of winemaking but very necessary to ensure that no wild strains of yeast or bacteria would enter the juice. ML bacteria was added a day before the press so that it could benefit from being evenly distributed in the juice during the pressing process.

Sanitizing 

There were three batches of must at Steve's house that day, ready to be pressed. Steve pulled out his beautiful press from the turn of the 20th century. It belonged to his grandfather and was quite the treat!

Our must had been in primary fermentation for about ten days at that time. We poured the must into the wine press and let the juice flow into a container at the bottom of the press. This is what is known as the free run. Following that, we placed heavy blocks of wood onto the crushed grapes and exerted pressure to press the remaining juice out. The unfinished wine went into the sanitized carboys and gallon jugs, that were then air-locked.

Beautiful wine press and free run

Pouring pressed wine into carboy

The day ended with a quick sampling of the three different juices. Within only ten days, you could already taste the difference among them. Some of us (not me) had clearly done a better job with punch downs and keeping the temperature at the higher and more desired range. Those juices showed a bit more tannins and structure. My juice, which was fermented cooler and with less intervention, was more fruit-forward. I can't wait to see how our wines will continue to evolve.

My Verdict: I was a skeptic when it came to winemaking. Given the abundance of great wines available, there is hardly any need to make my own wine. However, I've been having great fun so far. I've also learned a lot about what goes on in a wine. Stay tuned for my post on secondary fermentation and bulk aging.