94202
Scientists had known since the early 20th century that rats could not survive on a diet whose only protein source was zein , which comes from maize ( corn ) , but recovered if they were fed casein from cow 's milk .
 maize
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 maize