I'm not any big food expert or anything but when I was a kid we worked out in the mint fields (there's more than corn in Indiana!) and we always packed a lunch that would sit in the hot sun till lunchtime and we never, ever, got sick. PB & J and even lunchmeat. BUT, now that I am an adult, and even moreso now that I am a nurse, I don't think it's too wise. If you can't find single serve jelly in the flavors you like, check with your local hospital. We have lots of different flavors. I'm sure they would be willing to sell you a few. If nothing else, you could get small cheap jars and open them at the park and pitch them when you're done (with a fresh one each day) and still be $$$$ ahead of buying food in the parks.