A zuurtje is a hard candy made by boiling sugar and mixing it with an acid, such as lemon juice or citric acid. The name — literally "little sour one" — refers to this method rather than to the taste: most zuurtjes are sweet with a fruity edge, and only some are genuinely sour. It is the Dutch equivalent of the English boiled sweet or the American hard candy, and the word is also used loosely for any small, clear, fruit-flavoured hard sweet.
How they are made
Sugar and glucose syrup are boiled until almost all the water has gone (the "hard crack" stage, around 150°C), after which acid, flavouring and colour are worked in. The hot mass is poured onto a cooling table, kneaded or pulled while still pliable, and then shaped into a rope and cut or stamped into individual drops. Once cool, the sugar sets into a glassy solid. The distinction from borstplaat is instructive: borstplaat is sugar and water (or cream) left to crystallise into a fudge-like fondant, while a zuurtje is boiled hotter and kept clear.
Flavours and forms
Typical flavours are lemon (citroen), raspberry (framboos), strawberry, cherry, orange, blackcurrant (zwarte bes) and aniseed (anijs). Zuurtjes are sold loose from the jar, in bags of mixed fruit drops, and in tins. A zuurstok — the striped candy stick of fairs and markets — is essentially a large zuurtje, and the cinnamon kaneelstok is a close relative. Some modern sweets combine a hard shell with a sour powder centre, such as the lemon balls sold under the Napoleon brand.
German and Belgian cousins
German shops sell the same kind of sweet as Bonbons or Drops — confusingly, in German "Drops" means fruit hard candy, not licorice, while in Dutch drop means licorice. Shoppers looking for "Duitse zuurtjes" (German boiled sweets) are usually after these fruit bonbons or after the large tins of mixed hard candy sold in German supermarkets. In Flanders, boiled sweets are usually just called snoepjes; note that the babelutte of the Flemish coast is a caramel rather than a fruit drop.