Taking food to Europe

Are you checking luggage or doing carry on only? The jelly/jam would be a problem with carry on unless you can fit it in your quart liquids bag going thru TSA security.

Nuts could be an importation problem. I'd be sure to declare them with the thought that they might be chunked.

You should be able to find out about the nuts before you leave. A quick google netted some results. Spain follows the same import rules as the rest of the EU. What I read so far states there are no restrictions for the items you want to carry. Most of the restrictions deal with meat.

EDIT - I would definitely put jelly in checked bag or mail it ahead to where you are staying.

I always carry on if possible and have had the craziest things confiscated including jam/jelly (very special mango pineapple jam from Guatemala...still sealed) along with sealed spices, handmade candles from an abbey for my daughter's wedding....
all on different trips and with no reasonable explanation...I would only put them in a checked bag because once you get to security it is too late to do anything else.... and I don't want to argue with them. Other times I have brought stuff I thought they would take...
Edit: My stuff was all taken at security... not Customs and it was flights to the US at various airports, not leaving.

Apart from the liquids in carry-on rule (airport security at Schipol confiscated some jelly from me last year doing a connecting flight), there shouldn't any problem with Customs going into the EU as it usually just a walk through. It's more of a problem reentering the US as US customs is more strict about these things.

I checked homemade jelly and it made it through to Naples without a worry. 2013 summer.
If you are doing the Georgia pecan thing, if they can ship it for you (like a special company), or at least you would know. Note: sometimes it the things are put into a product (e.g. pralines) it's not the same and your chance of clearing customs would be enhanced. You can truthfully call them "praline cookies" rather than nuts, and declare them.

I think it would make a tremendous difference if the nuts were sealed in a factory bag, especially if they are labelled "Roasted". I don't want to get into an organic food debate, but there are occasional ... er ... worries ... about the unroasted hippie bulk-nut bins (sorry) in various health-food sections of American stores. We're talking here about avoiding disappointment with government employees who may speak English as a Second Language, not debating how healthy raw food may be for us!

I have lived oversea for 14 years and have probably taken the equivalent of half a grocery store to Europe in that time. Unlike the US where customs is a manned, form-oriented process, when you enter Europe you just walk through customs and you choose whether to declare items or not. Pecans are a great idea as they are highly unusual and very expensive in Europe (I have spent upwards of 20 Euro at a gourmet grocery to make a pecan pie!). Similarly, I have taken homemade jelly into the US and didn't have any issues.

I think the concensus is that you should be OK. As others have said, you can check EU Customs sites for some guidelines, Meats for instance are frowned upon, but I have taken the equivalent items back and forth, even declared them at the US border with no issues.

You should certainly have no issues on leaving the US except at security with the Jellies, so put those in a checked bag.

Arriving, It would be very rare that you are submitted to a Customs search, most places leave it at "if you have something to declare, come see us". Not that you should sneak something in that is not allowed, and many airports do monitor checked bags during handling, but as has been said, your items are pretty common.

I go to Spain about two times per year. I have carried the following with no problem: Shelled Pecans in the bag from the company, maple syrup in store bottles, Moon Pies in the wrapers, Candy, store bought, jewelry, model cars, books, and the list goes on..;..Never any problem, all in the main suitcases in the belly of the plane. The only problem was pecans that we had shipped separately...they were held up in Spain customs for several weeks...finally got to the destination long after we were back in the states!!! Never carried any homemade items. Pecans are very unusual in Spain....and now all in Georgia are shipped to the orient.

Bring back from Spain, Olive Oil, and Olive Oil Products...no problem as they are in the factory containers. Vinegar is treated as alcohol and must be declared. Even some jamon in the factory tight sealed package once, and made it through, luckily as it was delicious!!!

My standard host/hostess gift is a small jar (2-3 oz) of huckleberry jam, a fruit native to the NW. I wrap each jar in bubble wrap and then put each jar in a pint freezer ziplock. I stuff the bags into my extra pair of shoes or spare corners. Once I've given the jam, I save the bubble wrap & ziplocks and re-use w/ fragile mementos I bring home. I have always put the jam in my checked bag and have not had any breakage or questions from customs