1. The process of becoming sour
   "The souring of milk occurs when bacteria convert lactose into lactic acid"

1. Go sour or spoil
   "The milk has soured";
   - turn, ferment, work
    
2. Make sour or more sour
   "For example, acidulate fresh cream by adding lemon juice to produce sour cream";
   - acidify, acidulate, acetify

Derived forms: sourings

Type of: change state, change taste, spoilage, turn

Encyclopedia: Souring