For a milder salsa, ensure the jalapeno is thoroughly seeded before mincing. Adjust the amount to your spice preference. If you don't have fresh corn, you can use frozen corn kernels. Just thaw them before adding them to the salsa. To prevent the avocado from browning, you can toss it with a little lime juice before adding it to the salsa. This salsa is best served fresh, but it can be stored in an airtight container in the refrigerator for up to 24 hours. The avocado may brown slightly.