I don't worry about
organic. I buy local produce when it's things like sweet corn that I want fresh. You have to know what foods contain sulfites, and it doesn't matter if onions and garlic are organic because they have it naturally.
There are no safe brands, and products that were clean years ago have often changed because of using cheaper ingredients. I have to make my own jams and jellies because all the commercial ones use bottled lemon juice and corn syrup. I'm going to try making pickles with rice vinegar because all the other vinegars have sulfite.
As for packaged prepared food - read the labels and calculate how much sulfite is in a serving. Then compare this with your daily tolerance. Don't know how to find this? Read the free book online at http://www.learningtarget.com/nosulfites/book.htm
For those who read the book years ago, I suggest re-reading as it's changed a lot.
My tolerance is about
2000 micrograms a day, but not all at once! This is not as low as the book author's but my reaction is not the typical headache. As soon as sulfite hits my mouth or esophagus I start getting an upset stomach that triggers tachycardia, which has sent me to the hospital several times.