[go] sour
1
(of situations, moods, or relationships) to become unpleasant or unsuccessful
The idiom "go sour" is thought to have started in the early 1500s from the way people saw milk turn sour, which happens naturally because of bacteria. Milk that is sour is not good anymore and it tastes bad, so people started using this idea to describe other things that were not good or that got worse. Over time, the phrase became common in informal contexts and is now used to mean that something has changed for the worse.
- Unfortunately, their friendship started to go sour after a series of misunderstandings.
- The collaboration between the two teams began to go sour due to conflicting interests.
- Their romantic relationship went sour when they realized they had different long-term goals.
- Things started to go sour between the business partners when financial issues arose.
- His relationship with colleagues went sour after a disagreement over a project.
2
(of food or drinks) to become unpleasant in taste or smell
- I left the milk out overnight, and it started to go sour.
- Be sure to check the expiration date; yogurt can quickly go sour.
- If the mayonnaise smells odd, it might have gone sour.
- The cream in the recipe went sour, so I had to discard it and start over.