What's the difference between DOC and DOCG wines in Italy?

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Dear Dr. Vinny,
What is the most important criteria for distinguishing between DOC and DOCG wines in Italy?
—Miguel, Somerset, Pa.
Dear Miguel,
The Denominazione di Origine Controllata e Garantita (DOCG) is the highest designation for Italian wines, while the Denominazione di Origine Controllata (DOC), has less strict guidelines.
The point with both of these systems is that there are multiple criteria—not just a single distinguishing factor. DOC wines are regulated for not just the type of grape and where they are grown, but also harvest yields, alcohol levels and the use of barrels. The rules for DOCG are even stricter than DOC—yields must be lower and the wines must be aged in barrels longer, for example. And DOCG includes requiring the wines be submitted for technical analysis and tasted for approval by a government committee before they can be sold as DOCG wines. The DOCG wines even have a numbered, government seal across the neck of the bottle to prevent counterfeiting.
While both of these designations are a helpful start to looking for quality wines from Italy, keep in mind that DOC or DOCG wines might not be to your liking (or your wallet’s) and there are plenty of wonderful Italian wines that carry neither seal.
—Dr. Vinny