(Wine-Searcher) - Poor information about Prosecco means consumers care less and less about quality differences between the DOC and DOCG wines, argues Jeremy Parzen.

"We craft this wine using only the best Glera grapes, the official grape of Prosecco, from our vineyards in Italy," writes Cupcake Vineyards on its website.

The editors of the Livermore, California-based megawinery's e-commerce portal are referring to its Prosecco DOC, one of the most highly visible expressions of Prosecco available in the United States today. It's a wine that you can find as readily on the shelves of "big box" stores as you will on those of upscale specialty food stores like Whole Foods.

But when they write that they use "only the best Glera grapes", one can't help but wonder if they are talking about fruit sourced from the three historic hilltop villages where the wine's popularity was initially forged, or fruit grown on the valley floor of Treviso province; or even as far away as Friuli-Venezia Giulia, where sparkling Prosecco is a relative newcomer.

When it was launched in 2009 by the Prosecco growers consortium, the Prosecco DOCG was intended to help consumers differentiate between the lower-quality Prosecco DOC and top-quality DOCG. The former are produced using fruit grown on the valley floor while the latter are made from the slope-blessed townships of Valdobbiadene, Conegliano, and Asolo.

With steep vineyards, abundant southern exposure, stony, glacial-era morainic subsoils, and a breeze that arrives from the Adriatic to the east, the Conegliano-Valdobbiadene Prosecco DOCG and the Asolo Prosecco DOCG offer the ideal conditions for obtaining fresh wines, with vibrant acidity and signature minerality.

During the 1990s, as the Conegliano-Valdobbiadene Prosecco boom began to sweep English-speaking countries, more and more growers planted Glera on the valley floor where vineyard management and harvest costs are significantly lower.

By the mid 2000s, the top shippers of Prosecco felt enough was enough. Their consortium proposed a new DOCG that would cover only the best townships for growing Glera. In return for the right to add the prestigious "G" to their DOC, they would allow an expansion of the DOC that would include the entire region of Friuli-Venezia Giulia to the northeast, where sparkling Prosecco was already emerging as a new category for the area.

Data is still not available for the 2014 harvest but, according to last year's numbers, roughly 70 million bottles are produced annually in the DOCG while 230 million are produced in the newly expanded DOC.

Today, four years after the first bottles of Prosecco DOCG were released, there is regrettably little understanding among consumers regarding the differences in provenance and in quality