Final answer:
Citric acid and acetic acid are used to prevent cooked sugar from crystallizing. Both acids add a tart flavor to foods and help maintain the desired texture in sweets by inhibiting sugar crystals.
Step-by-step explanation:
Two acids that are used to prevent cooked sugar from crystallizing are citric acid and acetic acid. Citric acid is found in citrus fruits and plays a role in metabolism, while acetic acid is the main component of vinegar. Both of these acids can provide the tart flavor to foods and help in the preservation process by inhibiting crystal formation in sugar syrups, which is crucial for confectionery and dessert preparations.