Narrow search terms: type of food, name of food item, name of a dish, name of ingredient.
The * is a wildcard that searches for any letters that might follow, e.g. eat* will find eat, eats, eating.
Other Relevant Info
Don't forget to think about additional elements of your topic that can be useful search terms: region of the food; type of food; people who grow, prepare, sell, or consume the food; labour or technology related to the food.
What kind of approach are you taking to your topic, what aspect of food are you writing about: history, culture, nutrition, medicine, economics, politics, etc.? The approach can help to determine more keywords for your search.