The most common food product with ammonium sulfite is caramel coloring E150d.
According to the FDA, caramel coloring contains ammonium, potassium, or sodium sulfite.
The bricks made using ammonium sulfite are mainly used for blast furnace linings.
[8] Ammonium sulfite can be included in lubricants for cold metal working.
The lubricants are intended to reduce friction to keep heat production down and keep impurities out of the metals.