The aftertaste is very subtle, one might describe it as tangy. If you are an American and have never had foreign chocolate, you've probably only ever had chocolate with with milk that has undergone lipolysis; and you'd likely never notice it. For the first 5 years of my life I was raised in foster care by naturalized Europeans, so my formative years involved Swiss chocolate whenever I had it. Swiss chocolate uses milk that has not undergone lipolysis, and their chocolate is very smooth due to a process called conching. Conching is a mixing process with lots of heating and aeration which allows organic acids to evaporate creating a very uniform and smooth textured chocolate without bitter or tangy afternotes.