This is a question I get asked a lot, and one of my favourite ones to answer. There are several reasons why chocolate in the US tastes particularly disgusting to non-Americans.
"Butryic acid is found in milk, particularly goat and sheep milk but also in human vomit, giving it its distinctive smell"
The main reason is because of the milk. When Milton Hershey first started making chocolate, the milk he was using had gone sour, so rather than waste it he dehydrated and used it anyway. People bought his chocolate bars and seemed to like them so he didn’t want to change his recipe. However, rather that using sour milk today, it’s thought the company uses a process that adds butyric acid to its chocolate which gives it that sour taste. Butryic acid is found in milk, particularly goat and sheep milk but also in human vomit, giving it its distinctive smell.
In the UK, Cadbury uses whole milk in its Dairy Milk bars, which starts to caramelise in the process of making the chocolate and that’s why the chocolate tastes more creamy.
Another reason is because US companies don’t tend to use as much cocoa as companies like Cadbury, which means the chocolate tastes slightly different (in the US chocolate needs a minimum of 10% cocoa while in the UK the figure is 30%). There are also slight differences in the definitions of cocoa content and how it’s sourced in each country. In the US cocoa means non-fat cocoa powder, whereas in the UK it includes cocoa powder and cocoa butter.
The reason Cadbury tastes different in the US is because it’s licensed to Hershey and the company uses a slightly different recipe than we’re used to in the UK. Last year a company was banned from importing Cadbury chocolate from the UK into the US as the move infringed on Hershey’s licensing agreement.