Do airlines recycle uneaten, unopened, pre-packaged food?

I understand why prepared food (e.g. the main meal or the salad) has to be thrown out if uneaten, but what about all the pre-packaged stuff, like the butter and/or jam, cheese bites, chocolate biscuits, yoghurt, milk, water, orange juice etc.? Once the flight attendants collect your tray at the end of a meal, does it all just get thrown out or is it somehow checked and recycled or donated?

I'm guessing there are quarantine laws and health regulations that might make this a pain, especially internationally, but it also seems like an enormous amount of wastage. I, for instance, never eat the yoghurt or use the butter.