Would food cooked with the intention of reheating and eating some of it now, some another day, with the second part stored promptly and properly (packaged,canned,refrigerated or frozen) after preparation (never served on a table prior to storing, nothing taken from the cookware to taste with any unclean utensil) be considered the kind of leftovers that hinduism discourages eating?
In the believers of sanaadhana darma,
what you eat is what you are is very much emphasized. In an essence, like our physical body is affected by the ratio and balance of vaadha, pitha and kabha, our physiological aspects are affected by the ratio and balance of three gunas; saathvik, rajas and tamas.
In order to promote saathvik and inhibit the other two it is advised to have foods that aids this process. Accordingly scholars have provided a guidelines of what to eat, what not to and all the FAQs associated with it.
One such scholar is Sri Vedanta Desikar who authored a guide called
Aahaara niyamam where Aahaara means the food and niyamam means regulatory guide.
As per that guidelines it is to avoid reheat; one days food should not be shared and the list goes on. There are some interesting exceptions as well.
The site Anudinam.org has a beautiful article published on this topic.
As per that guidelines, the food has to be eaten before the warmth goes off. Once the warmth is off it is considered to be tamasic; an exception of this the rice soaked in water and food stuffs like sweets.