It says there that it contains "celery juice".

"Celery has a very high concentration of natural nitrate, and treating celery juice with a bacterial culture produces nitrite. The concentrated juice can then be used to produce “no nitrite added” processed meat."

https://www.mcgill.ca/oss/article/food/celery-juice-viable-a...

doesn't it just have nitrates from the celery?

The celery juice is added after cooking and the jerky is eaten cold. But yes, the celery juice will have nitrates -- the human body will naturally produce nitrites anyway -- the concerns are about heating the nitrites -- e.g. frying bacon.