ISTANBUL -- Nadir Güllü is worried about pistachios. The owner of Güllüoglu, the world's most famous baklava shop, uses bushels of the shelled nuts as the key ingredient for his popular desserts every day, but he is concerned about low-quality nuts from neighboring Syria saturating the market ever since that nation's civil war broke out in March 2011.

For Nadir, 59, and his Istanbul family business, pistachios are everything. People from all over the Middle East come to his shop for the rich, sweet dessert made of layers of filo pastry filled with chopped pistachios and sweetened with syrup or honey. And these are no ordinary pistachios, Nadir notes. For 141 years, his family has used only the high-quality pistachios from Gaziantep, Turkey, the pistachio and baklava capital of the world, located about 60 miles north of Aleppo, Syria. In order to protect the third-largest pistachio producer in the world, Turkey prevents foreign imports.

Baklava
Pistachio baklava. Güllüoglu

But in recent years the quality of the local pistachios -- and therefore the taste of the baklava -- has been compromised.

Nadir Güllü
Nadir Güllü and son Murat Güllü. International Business Times/David Kashi
Güllüoglu
Güllüoglu Baklava shop. International Business Times/David kashi

“If you look at the pistachio when you crack it, you see the inner color, which should be a dark green,” said Nadir's son Murat, 25, inside the family shop located just steps from the Bosporus. “The pistachio from other parts, like Iran and Syria, are yellowish, and that means there is no taste in it. The flavor in it is less, the aroma and taste, and when you eat it you feel the difference.”

Nadir Güllü
Nadir Güllü, owner of Güllüoglu, smells the pistachio grinds and explains why Gaziantep pistachios are the best in the world. International Business Times/David Kashi
1Nadir Güllü
Nadir Güllü, owner of Güllüoglu, smells the pistachio grinds and explains why Gaziantep pistachios are the best in the world. International Business Times/David Kashi

For the Güllüs it has become increasingly difficult to find pure Gaziantep pistachios because lower-quality nuts have managed to slip in through new smuggling routes, the same lanes where refugees, drugs, weapons and oil have been passing because of the Syrian conflict.

Nadir Güllü3
Nadir Güllü, owner of Güllüoglu, eats pistachio grinds and explains why Gaziantep pistachios are the best in the world. International Business Times/David Kashi

The Güllüs suspect that suppliers are now cutting pistachio grinds and selling them to baklava makers throughout Turkey -- mixing the high-quality Gaziantep ones with the lesser ones from Syria.

Gaziantep
Gaziantep pistachio grinds from Güllüoglu. International Business Times/David Kashi

Murat said that if Güllüoglu started to use the cheaper cut pistachio, his customers would immediately taste the difference. “We cannot use a poorer quality," he says. "It’s not ethical for us.”