Exactly right - the nitrogen gets incorporated into the steel’s crystalline structure during heat treatment, making it slightly harder without leaving any toxic residue behing.
Black raspberries have way more antioxidants and a more intense wine-like flavor that makes them amazing for jam (they’re my favorite to preserve becuase of that depth).
Those look amazing, nothing beats foraged berries for flavor! Pro tip: freeze any extras flat on a cookie sheet before bagging them up so they don’t clump together, that way you can grab just a handfull for pancakes whenever the craving hits.
Fish skin is literally one of the most nutritious parts too - packed with omega-3s and collagen that’s great for your skin and joints, such a waste when peole toss it!