I have a recipe for broiled swordfish steak that uses the following ingredients for the baste: olive oil, butter, Dijon mustard, white wine vinegar, and black pepper.
I only have garlic-flavored red wine vinegar (no lemon either). Can I use that or would it be better to skip the vinegar altogether?
Vinegar, in general, has distinct acidic characteristics that will affect a recipe; it's often used for this reason. For instance, in marinades, the acid is used to break down muscle fiber and help flavor penetrate. In Cevice, the acid component is used to "cook" the fish.
Additionally, the different types of vinegar have different flavor characteristics. I, personally, don't much like red wine vinegar as I find it kind of bland. I much prefer balsamic or champagne. So the question you really need to ask yourself is, "will the flavor of the red wine over the white wine adversely affect my dish?" You might ask the same question about the garlic.
So subbing one type of vinegar for another is fine if you're looking to replace the role of the acid in a recipe (also why you can sub lemon juice). Whether or not you feel the flavor can be substituted is really just a matter of personal preference. If you don't know ahead of time about the flavor, try it and find out for sure.
To specifically answer the flavor characteristic for your question, I'd say yes. Red wine is OK. As pointed out, swordfish is a hearty fish and should hold up fine. I probably wouldn't sub balsamic, would use champagne as a priority, would think long and hard about apple cider. If it was a lighter fish, I'd be much more wary about red wine.
Red wine vinegar has a much more pronounced, grape/fruit flavor than white. I normally wouldn't recommend it for fish... except maybe swordfish which can hold up to a ton of flavor. I'd personally just use lemon juice instead.
Both answer's already given show how subjective cooking can be (I can agree with parts of both of them).
In this specific case (mustard + vinegar), I'd make sure my mustard + red vinegar combination don't result in an ugly brown. As mustard's also adding it's taste, I prefer 'clean tasting' vinegar (or lemon juice).
I agree that a lemon juice might be better than red wine garlic vinegar, esp if you weren't looking for garlic. If garlic is part of the equation anyway, then go ahead. Swordfish can get dry, so don't leave off fluids that can fight the dryness, and be careful not to overcook.
