Food

In MahA Bharatham, Lord KrishNA answers DuryodhanA's query on why He did not eat at his palace and instead ate at VidhurA's house. The Lord explained:

sudhdam BhagavathAsyaannam suddham Bhageerathi jalam I
suddham VishNupadha dhyAnam suddham EKAADASI VRATHAM II

(MEANING): The food partaken at a BhakthA's house is superior and pure. At the same level of holiness are the intake of 

1. GangA theertham, 
2. VishNu DhyAnam and 
3. EkAdasi vratham.

'The food 

1. over which one sneezed, 
2. that in which there are worms and insects, 
3. that which may be mixed with any leavings of dishes, 
4. that which is mixed with hair, 
5. that which is mixed with tears, 
6. that which is trodden upon shall form the portion of these Rakshasas! The learned man, knowing all this, shall carefully avoid these kinds of food. 

http://www.sacred-texts.com/hin/m09/m09043.htm