"There's no need to think too ill of people," the Young Madam said as she asked her maid to bring out a silver needle to test for poison. "Won't we know if there's any poison if we test it with a silver needle?"
The food that these wealthy families consume is always chosen with great care. Life is most precious in a wealthy family, and the food and items they use are selected with particular attention, naturally, they also fear that their adversaries might poison them.
They are even more afraid of bandits infiltrating or some other human-caused calamities; every day, the food that the master's family eats is tested for poison before consumption.
Especially the Madam, who wields the authority of a housekeeper over a family; she is very cautious with the food of her husband and son. It's not unheard of for there to be strife within large families, and their family has its share as well.