Journal or Book Title
A somewhat unusual aspect to "cured" natural and organic processed meats is that nitrate and nitrite cannot be added as ingredients, because "preservatives" are not permitted in natural and organic foods. This has resulted in alternative meat-curing processes that utilize natural sources of nitrate, typically celery juice concentrate or powder.
Sebranek, Joseph G. and Sullivan, Gary, "Properties of Natural and Organic 'Naturally Cured' Meats" (2013). Animal Science Publications. 105.