Hi Mark, We can certainty describe the taste of drinks. Some drinks such as coffee give off an aromatic smell, and we can describe the smell of coffee (or roasted coffee beans) as well as the taste of coffee (this coffee has a rich acidic taste.) When foodstuff rots, we usually say they give off a "bad smell" or "smells rotten". We don't usually say that they smell sour. Some liquids can "taste sour" when they are rotten. For example, the milk tastes sour.

Yes, "sour" is a specific taste sensation, so it can apply to drinks or food (or something inedible if you like, say strong acid). To say the "beef has gone sour" can be used, but I tend to hear more "the beef tastes bad". Anything that has the words "gone sour" usually implies the item has gone bad. You can say something "tastes sour" to imply something is naturally sour or gone bad, but if you say "gone sour" it is most definitely bad.

'Sour' is not necessarily a negative word, and it doesn't suggest that something has gone bad. A touch of sourness can enhance the flavour of food or drink. You could use the word 'rancid', though. This can be used to describe the taste or smell of any fatty food (meat, milk, cheese) which has become stale and unpalatable. 'This beef tastes rancid'. We tend to use the expression 'go sour' in an idiomatic rather than literal way. For example, if a personal or business relationship began well but then deteriorated, we can say that it 'went sour'.

It's not really common to say food is sour. You can just say "The beef went bad" or "the beef is bad" we also use stale for bread and potatos like potato chips when you can't eat them anymore