Sour candy can be addictive, whether you like hard suckers or chewy, jellied types with crunchy skins. To make your own version of the jellied sour treats sold in movie theaters, use a tart-flavored jam such as orange marmalade or sour cherry as a base. Food coloring sets the mood, while adding citric acid to both the candy and its sugary-tart coating enhances the sourness. For a more old-fashioned option, use lollipop or rigid candy molds to create hard candies that also rely on citric acid for sourness, as well as food-grade citrus, sour apple or tart cherry flavorings.
Butter an 8-inch square baking pan.
Whisk together, in a saucepan, four parts tart jam, three parts sugar and two parts water. Add about one packet of unflavored gelatin for every 1 cup of the jam mixture.
Turn the burner to medium and bring the mixture to a boil, stirring constantly. Once the mixture comes to a boil, continue stirring for 2 minutes.
Remove the sour candy mixture from the heat and insert a cooking thermometer into the mixture. Wait for the temperature to come down to about 260 degrees Fahrenheit. At this stage, add a pinch or more of citric acid, depending on how sour you like your candy. You can also add a drop or two of food coloring at this stage.
Pour the sour candy mixture into the buttered pan. Place the pan into the refrigerator for about 3 hours, or until the mixture firms.
Stir together equal parts cornstarch and powdered sugar and scatter this mixture over a large piece of wax paper. In a shallow bowl, mix a spoonful or two of granulated sugar, as well as a pinch or two of citric acid.
Remove the sour candy from the refrigerator and use a knife to loosen the sides. Gently remove the firmed-up block from the pan and place it onto the dusted wax paper. Turn the block over so that both sides are coated with the cornstarch and powdered sugar mixture.
Cut the block into 1-inch squares, and then dredge each sour candy piece in the bowl of combined granulated sugar and citric acid. Turn each candy over so that both pieces are covered.
Dry the soft sour candy pieces on a wire rack until they harden, and then store in an airtight container.
Spray candy molds with a light coating of cooking oil spray.
Whisk together, in a saucepan, two parts sugar and one part each light corn syrup and water.
Turn the heat to high and stir continuously. Clip a cooking thermometer on the pan once the mixture comes to a boil, and keep cooking until the mixture reaches 300 degrees Fahrenheit or the "hard crack" stage -- the mixture will separate into threads when pulled.
Take the pan off the heat. Drizzle in a small amount of green apple flavoring or food-grade oil of lemon, lime, orange or tart cherry, as well as a drop or two of a complementary food coloring. Add a pinch or two of citric acid, to taste, and stir well to combine the flavorings and colorings.
Pour the liquid sour candy mixture into the candy molds. If desired, add a lollipop stick in the center of each piece of candy. Cool to room temperature, and remove the sour candies from their molds.