What can be taken out of Istanbul?

Current customs rules are here: https://help.cbp.gov/app/answers/detail/a_id/82/noIntercept/1/session/L3RpbWUvMTM4OTgxMTU5MC9zaWQvdV94eW9zS2w%3D and appear to allow both coffee and spices in general, but there are some limitations related to spices.

I'd caution you about spending much money on such products in non-commercial packaging. I believe the customs rules were pretty similar 20-30 years ago when I brought back a very small stapled (not sealed) plastic package of saffron from Spain. The inspector allowed me to keep the saffron but let me know that the packaging really wasn't acceptable. I have no idea why it played out that way, or whether there have been changes since then. Based on the above link, I'd have no hesitancy in bringing back coffee or spices in sealed plastic or glass containers.

I'm surprised not to see any limitations on packaging at the link I posted. I thought there were such rules for things like cheese, at least.

Are you expecting to be checked on departure by Turkish customs agents who might limit what you have purchased? Didn't happen to me, but that's several years ago. Usually it is the country that you enter, not exit, which enforces its own regulations, in your case the US.

In line with the rules on the above link, I bring home European cheese every year, and declare it to customs & agriculture, and have never been checked. The same goes for dried mushrooms and dried spices from various regions.

What you can't take out of Turkey are antiquities: see http://turkey.usembassy.gov/cultural_artifacts.html.

I was in Turkey this past fall and I think you can bring spices back but they needed to be packaged a certain way to get them into the US. Sealed somehow and not just wrapped up. I sort of remember this being the case.

When I was Istanbul in 2011, my mother bought some spices from the Spice Market. The seller explained that he would seal the package in such a way that it would be fine for bringing into the US, but that it could not be brought into Australia (I forget the other details, but he also knew about Canada and New Zealand). Of course, we were prepared to lose the package if it was not admitted (we realized his information may not be - let's say, totally objective - since he had a sale to make), but we declared it and it was fine.

BTW, even though the package was sealed, it still had an aroma that was evident, so there was no way we could avoid declaring it (the dogs were definitely on it).

Thank you !!!

You can even take live horse from customs in Turkey. They are a joke!
Put even 30 kg spices in your luggage, it wont be problem. It may be problem in usa customs not in Turkish customs..