Line a baking sheet with greased baking parchment.
Wash and clean the raspberries, then press them through a fine-mesh sieve to produce 1 dl raspberry puree.
Soak the gelatine sheets in cold water and set aside.
Combine the raspberry puree, sugar, syrup and water in a saucepan and bring to the boil over a high heat. Boil for 5-6 minutes and then take the saucepan off the heat.
Squeeze the water from the gelatine sheets and fold them into the hot raspberry mixture.
Add the citric acid and stir.
Use a spatula to spread the mixture thinly on the sheet. Leave to set at room temperature for at least 2 hours.
Mix the sugar, citric acid and lime zest.
Use a sharp knife to cut the raspberry mixture into strips about 2 cm, and roll in the sugar mixture.
Store the raspberry straps in a large, unlidded container at room temperature.