The article addresses this and claims that the product it's talking about doesn't contain nitrites at all.
> In the US, there has been a clampdown on bacon marketed as “uncured”, which has been spiked with celery or other vegetable extracts instead of the E numbers. It may sound healthy, but it’s not. Like many vegetables, celery is a source of nitrate, and a concentrated extract can indeed stand in nicely for the usual additives. But the end product still contains harmful levels of nitrates, and can now no longer be labelled as “uncured”, or “no nitrate or nitrite added”.
> Prosur’s secret ingredient isn’t the only nitrate-free colour enhancer on the market.