From a food safety perspective, frozen foods can remain safe to eat indefinitely if stored at 0°F (-18°C) or below. Therefore, a turkey that has been stored in a deep freezer for over a year, as long as it has been continuously kept at the recommended temperature, should still be safe to eat.
However, the quality of the turkey may have deteriorated over time. Freezer burn, which occurs when moisture evaporates from the food and leads to dehydration, can affect the texture and taste of the turkey. The meat may become dry and develop off-flavors.
To determine if the turkey is still suitable for consumption, examine its appearance and smell. If there are extensive signs of freezer burn, such as discoloration, dryness, or a strong off-putting odor, it's best to discard it. If the turkey appears to be in good condition, you can proceed with thawing and cooking it following standard food safety guidelines.
While the turkey might still be safe to eat after a year in the freezer, it's important to remember that quality may have been compromised. If you have any doubts or concerns about the turkey's safety or quality, it's best to err on the side of caution and choose a fresher option.