What do "pH" and "TA" numbers mean to a wine?

Hello there! I'm Dr. Vinifera, but you can call me Vinny. Ask me your toughest wine questions, from the fine points of etiquette to the science of winemaking. And don't worry, I'm no wine snob—you can also ask me those "dumb questions" you're too embarrased to ask your wine geek friends! I hope you find my answers educational, empowering and even amusing. And don't forget to check out my most asked questions and my full archives for all my Q&A classics.
Dear Dr. Vinny,
When I'm looking at the technical details on a wine, what do "pH" and "TA" numbers mean? What would be good numbers for each in a full-bodied wine?
—David P., Mission Viejo, Calif.
Dear David,
Let me take you back to science class. PH is the measure of the degree of relative acidity versus the relative alkalinity of any liquid, on a scale of 0 to 14, with 7 being neutral. Winemakers use pH as a way to measure ripeness in relation to acidity. Low pH wines will taste tart and crisp, while higher pH wines are more susceptible to bacterial growth. Most wine pH's fall around 3 or 4; about 3.0 to 3.4 is desirable for white wines, while about 3.3 to 3.6 is best for reds.
TA, or "total acidity," is another way of looking at similar things, this time measuring acidity by volume. How do they relate? The higher the pH, the lower the acidity, and the lower the pH, the higher the acidity. Most table wines will have a total acidity of about 0.6 to 0.7 percent.
While these numbers might mean something to chemists and wine geeks, it's important to remember that the way a bottled wine tastes is about the relationship of things like pH and TA to other factors like alcohol, tannin, extract and sweetness. There's no chemical formula to make great wine—not yet, anyway.
—Dr. Vinny