Senior citizens may refuse to eat food prepared by a cook

Senior citizens who are 80 years or older cannot cook themselves since they have problems standing, yet require food regularly to remain in good health. Their children may keep a cook, yet their enemies may bribe the cook to add poison to the food for slow poisoning.
So some paranoid senior citizens refuse to eat the food prepared by a cook. The food which is prepared remains untouched and is wasted.
Then the children are forced to terminate the services of the cook to avoid wasting money in food material and the services charged by a cook for cooking.