In English we also use the definite article to say something about all the things referred to by a noun. The raspberry is a sweet berry= Raspberries are sweet berries. Hence the "The" is required in the English translation. "A raspberry..." also makes sense and ought to be accepted but not "Raspberry..." with no article. That's more likely to be referring to a flavour, essence or colour. Raspberry is a sweet flavour(of ice cream for example).