(Decanter) - A new film tracking the journey of Zinfandel from its Croatian roots to its status as a signature grape variety of California has debuted at a packed screening in the US state.

Dossier Zinfandel features several high-profile figures in California’s wine sector, including Paul Draper of Ridge Vineyards and Ravenswood founder Joel Peterson.

Mike Grgich, of Grgich Hills Estate (pictured) and who is credited with making the connection between California Zinfandel and the indigenous grape varieties of his native Croatia, also appears prominently in the film, which premiered at the recent Napa Valley Film Festival.

The film describes how Zinfandel had been considered a ‘state grape’ native to California. In the 1980s, in particular, millions of gallons of sweet White Zinfandel became ‘an introductory wine for a lot of Americans’, says Tim Mondavi, son of Robert Mondavi and of Continuum Estate.

Action then moves to Grgich and a team of scientists on a search of old vineyards along Croatia’s Dalmatian coast.

In 2001, researchers found an identical genetic match between Zinfandel vines in California and Croatia’s native Crljenak Kaštelanski.

Carole Meredith, the former UC Davis geneticist responsible for confirming the match between Zinfandel and the Croatian Crljenak Kaštelanski, told decanter.com that the film could have said more about Zinfandel’s history as an important commercial grape.

‘The film does not cover what we now know in terms of the ancient nobility of Zinfandel. Trade records going back to the 1300s all show that it was called by name [Tribidrag at the time].

'Varietal names didn’t really become important until practically the 20th Century, so it was really kind of remarkable.’