u/WhyNot4mine

I was checking my raspberry jam jars and found about a third of them have a strange discolored section in the jars. When I opened one of them, the top popped and was sealed. The jam wasn't moldy and smelled normal. What could cause this coloration in the jars? I'm wondering if it's safe to eat now. The jam was canned 3 years ago. All the other jars from the same batch look fine.