One of my recipes is fish balls. My question is how would you increase the protein content of it without affecting the taste?
I have very little sense of taste/smell and when I made it, it had the consistency of mashed potatoes.
you will change the flavor, you know, since anything you add will alter the recipe - even things with very neutral flavors will dilute other tastes. I'm guessing you want to not alter it much, encourage a similar flavor profile, or add things more neutral in flavor.
A few simple options - you can up the egg content (two eggs instead of one), as eggs have a high percent protein and there's one already in the recipe, so the flavor shouldn't change much (this might give you a bit firmer texture, your call on if that's a plus or not). You could lower the amount of potato (or up the amount of cod), so the percent of cod is higher in each ball. You could make a protein-rich sauce to pour on top (depending on what sauce or seasoning you usually use with it).
Alternately - you might try adding some protein powder (most of the ones I see are sweetened, so be careful). You might look for TVP or TSP (textured vegetable or soy protein) - which is very neutral in flavor and also quite inexpensive. I would recommend crushing to a powder before re-hydrating - this can be done with mortar and pestle, blender, or grinder, whatever you have - or blending afterward to minimize the texture change if you don't like it. You might add the tvp paste to the mix outright or substitute some reconstituted tvp paste (mixed with water or milk) for part of the mashed potato for a higher ratio of protein to carb.