Just throw another bite of unfinished dish to the garbage bin… Anyway you will have another portion in the evening and tomorrow, and may be the day after tomorrow. This is not a waste, just something you don't need - respect for the food. For something which was given by the Earth or something which was received while killing living organisms… You don't value this. It’s a waste. The waste of which someone is dreaming, because of starvation…
Later it was obvious to pray before you begin the meal. People were thankful to God for what He sent them to their plates, so the food had a big value.
Nowadays people lost the ability to appreciate the things they have and the same goes for food. "If I won`t eat it whole – I will bite a piece" became the motto of the society, where so-called "hospitality" is transformed into "festival of waste."
Perhaps, it is necessary to return to the wisdom of ancient philosophy and remember Socrates, who said that we do not live to eat but we eat to live.
It is better to share with those who need it, than to be hostage to his fridge; and remember that food is for eating, not for wasting.