First of all, I don't know who says that Yaffo has the best food in the Middle East, except perhaps for some particularly chauvinistic Yaffo residents -- and I've lived in Israel (including Yaffo) for 28 years now. There are certainly some good restaurants in Yaffo, but I wouldn't say they are any better than a lot of other restaurants in Israel (as for the rest of the Middle East, I only have experience of food in Egypt and Jordan, and a little bit of south Lebanon).
I've certainly encountered pre-packaged zaatar that includes citric acid, presumably to add sourness to the sumac (although not very often); but I've never seen pre-packaged zaatar that includes parsley. Typically, stuff you buy at the supermarket includes the zaatar itself (technically, it's hyssop in English), sesame seeds, sumac and a little olive oil. At one foodie heaven where I sometimes shop in Ra'anana, they also sell bulk zaatar with added garlic.
However, it's also worth pointing out that there is (usually) a difference between pre-packaged supermarket zaatar and the stuff you buy in market stalls, which tends to be the pure herb. In Amman, for example, I bought a biggish bag of zaatar that was pure dried hyssop with no additives. As far as sumac is concerned, I've bought it in bulk at the supermarket, and it is the real thing without additives (the only additive that wouldn't change the colour significantly is parika, but it would change the taste noticeably).
I went last week to Yaffo (also called Jaffa)--one of the oldest cities in Israel, where you can find the best food in the middle east (they say) searching for 100% real zaatar with no luck..They had "Zaatar" alright, or at least it looked like it and it is also the only thing people can get that is called Za'atar on the title of the package.
I've tried before expensive Supermarket Zaatar, or one from an original Spice shop, But if you can read Hebrew or Arabic, then you can find in the ingredients on the back of the package: PARSLEY AND CITRIC ACID!!!!
I WAS IN SHOCK!!
For the first time I have realized that I NEVER ATE REAL ZATAR although I was on the source.
Real Zaatar is not made with Citric Acid. The original recipe includes Sumac for the sour taste. And THE PARSLEY!?!?!? IS JUST TO GET CHEAP VOLUME!
Grose!
Therefore I have decided to make it myself. I even got fresh Zaatar, a special
Zaatar plant (Majorana syriaca) and not Thyme as many think, Authentic (relativley expensive) Sumac from the north Lebanon Border (grape looking/Red) and even grind that myself, because I even heard that most Sumac u get are mixed with something red to win on volume
-- because you can only trust what you make yourself from scratch. 

Edited by Tapenade, 22 December 2007 - 11:57 AM.