pH & Wine Quality

Whats the single most important number in winemaking? While many feel the specific gravity can be the most important, pH merits the title. pH is a factor in the wines entire life. Allison Crowe the "Wine Wizard" and PhD. In Enology, summed it up very well. "It is the backbone of your wine". It affects flavor, stability, aromatics, aging quality, sulfite requirements, and a host of other components in your wines overall structure. Lets take a look at some important dynamics of pH.

What is pH?
Scientifically, pH is the measure of hydrogen positive ions as well as the extent to which they disassociate. More simply put, it is a method of determining the strength of acid in a solution.

What is the normal range for pH in wine?
2.90 to 4.0
Most red - 3.4 to 3.7
Most Whites - 3.2 to 3.5
Sweet Spot - 3.55

There are many things in the vineyard that can influence pH. Canopy management, weather, soil composition, growing practices, etc. There are some things you can do as the winemaker to correct or compensate for pH values outside the target area.

Some examples are:

- Cold soaking, this can increase pH through extended skin contact

- Fermentation, alcohol has a higher pH than sugar, so it stands to reason that as fermentation progresses, pH will rise. Typically from .15 to .22 pH units

- Acid corrections - whether adding or de-acidifying, pH is always influenced by acid adjustments

- Malolactic Fermentation - as the harsh malic acid is converted to the softer lactic acid in the malolactic conversion; many wines will shift upward by about .20 pH units

pH is not detectable to our senses, one cannot "taste" or smell pH. pH does affect the taste of wine. Wines with a pH of 4 will result in flat tasting wines with little or no definition, wines with pH below 3.0 become excessively tart tasting

Perhaps the most important influence of pH is it effect on Sulfur Dioxide. pH is critical to determining the additions and the use of Sulfur Dioxide in our wines. Wines with lower pH values will need less free SO2 to achieve stability. Higher pH wines create a greater opportunity for unwanted microbes.
Wines with lower pH values will age slower than wines with higher pH values. As lower pH values also contribute greatly to long term color stability, knowing the pH value of a wine is one of the principle determining factors of how long you may want to cellar a wine before "releasing" it.

*Wine's with higher pH values will soften and age faster. They may tend to develop a brackish or red brick color around the edges. So lend consideration to "releasing" them sooner, rather than later. Be sure and use protective oxygen avoidance measures, and handle them more delicately. Avoid excessive splashing during rackings, or degassing.

Yeast Inoculation Dosages

A typical volume of must to complete a barrel of wine requires about 3 oz of yeast in most instances. As yeast is a bacteria, it is vulnerable to low pH environments, so increasing the dosage is advisable with pH values below 3.3. Go Ferm or other yeast rehydration nutrients are also important to assure proper yeast biomass and cell wall viability in the hostile environment of low pH levels.

It is plain to see why professionals closely monitor the pH values in their wines. Home winemakers can easily obtain an accurate pH meter to assist them. There are many models to choose from. Prices range from $50.00 for a hand held basic device to $500.00 for a professional style bench top model. Consider these factors when making your purchase.

Calibrates to 3 points, 4/7/10.
Readings in two decimal points
Automatic temperature compensation.

As you can see, pH is the most important factor in winemaking. Measure it, monitor it, record it.
You will make better wine.