Is it permissible for kitchen staff in government institutions to take unconsumed food or bread from their workday meals to their homes, knowing that they are exempt from paying for these meals and that these items might be preserved for another day and used by other workers?

It is not permissible for workers in government kitchens to take anything from the food under their charge unless there is explicit or customary permission. Taking anything is absolutely forbidden if the law stipulates so. An employee is entrusted (with responsibility), and it is not permissible for him to consume any food except that which has been authorized. The default is to prevent the employee from eating, as his wages suffice him.