Also, I found this article. In the cold opener, Carol dropped some food, including oranges, when she saw Walt.
Breaking Bad tips its cap to Godfather and lifts some themes from it. Oranges were used to symbolism death in the Godfather movies. It usually meant there was a death coming.
In the Sopranos Tony, who never eats fruit, was eating an orange at the beginning of the final episode. He also was buying orange juice in season 1 when the first attempt on his life went down.
We obviously know Walt is out for blood but I think the oranges that Carol drops are yet another sign.
http://www.destinationhollywood.com/movies/godfather/feature_oranges.shtml