I once heard that one can’t leave an open lemon in the refrigerator and use it again, is this true? Also in America does one have to sort through rice?
In the Shulchan Aruch it says that one may not leave liquid (water) out uncovered over night for maybe a snake will come and leave poison in it. (Yoreh Deah 117:1) I did not find anything about food. And if you want to say there is a problem with leaving fruit out as well, leaving it in the refrigerator should be considered that it was covered. It is just a very large box. With lemons there could be another problem of meat and milk for if one cut the lemon with meat knife the lemon should only be used for meat after that. So if you don't remember which knife you used or you didn't mark the lemon, the lemon shouldn't be used. One should check rice in America. I found bugs in grains when I was in Los Angeles.