The amount of nitrates in turnips can be very harmful to our body if reheated.
Turnip is potentially hazardous food that after we cook it shouldn’t be cooled and reheated again the second time, to avoid the food being at temperatures that support the growth of pathogenic bacteria. If pathogens were present in the food, they could multiply to dangerous levels.
You should always be concerned about bacterial growth, however, especially when you put away your cooked turnips on a room temperature for two hours or longer before refrigerating it. The two-hour mark is generally considered the point at which bacteria will begin to grow. Because turnips as already said contain a high amount of nitrates, just make sure that it is not left out for a long time and don’t reheat it. The best is to consume this vegetable fresh and well washed.