I think YABVU for the reasons already mentioned.
For those saying, give the op a break, we all lose our rag with our kids - yes that is true, but I think what's spurring such strong opinions is that the op hasn't written a post saying "I over re-acted and feel really bad". There's not much regret in the op. And at the time of writing, she was still angry.
Anyway, camperli, hope you don't feel too overwhelmed by the responses, try to take it positively, learn from it and move on. But personally I would try and lower my expectations and pick my battles. You are entitled to your opinions though, but perhaps what would have been less stressful for you, and less traumatic for your dd is if you'd just explained to her you don't like food waste.
FWIW, I came from a generation of "finish your dinner, there are people starving out there" and I'm now trying very hard to unlearn these messages that have caused me to over eat and not be able to leave food on my plate even when I'm full. I hate food waste too, but I now feel very liberated when I scrape my left overs into the bin (thank you Paul Mckenna!) knowing that I would have just forced it down my gob instead. Guilt around food, or any other negative feeling, should not be encouraged - it can spur a lifetime of unwanted eating habits.
FWIW, if I've really over stepped the mark, and I do, I personally do feel ds deserves an apology, an explanation and a hug. I think it goes a long way for ds and also helps me resolve it in my head and move on. I never spend too long on it or make it into a big issue. I try to stay in control as the authoritive parent, and say something like "I'm sorry for shouting at you ds, I shouldn't have lost my temper, I should have just explained it nicely. Now I will explain it nicely. I love you" end of. I don't really like the "they've probably forgotten by the morning" attitude. What if they haven't?
For those in favour of op, I don't personally agree with your opinions, but even if they are valid - this child is FOUR YEARS OLD. Give them a break. They've got so much to learn and take in. I don't think they need the shortage of food in other countries problem resting on their shoulders. And I'm all for discipline and teaching your child to show respect...but I would not expect that much of it from a 4 year old!!!