Why do commercial teas add citric acid?
There's no obvious purpose for it, and it makes me want to drink less tea because it doesn't go down as easy.
Preservative? What makes tea in a sealed bottle go bad? At least vinegar (acetic acid) in a hot sauce or dressing adds a nice flavor profile, citric acid doesn't do much for the flavor. I'd prefer any tartness come from actual lemons.
I find citric acid makes my throat a little raw and my stomach a little refluxy, something that doesn't happen with unadulterated teas or (for no clear reason) actual citrus drinks. It certainly cuts down on the chug factor.
Citric acid is a very, VERY common preservative, and one of the most benign as far as the chemical preservatives go.
Tea is a wonderful ground for bacterial/mold growth, ever leave a glass of iced tea out for a week or so and find the mold stuck to the glass and little rings of it floating on the surface? That's why the reservative.
a lot of the products use vitamin C (ascorbic acid, same function, lowering the pH) but if the bottle is clear vit. C can be destroyed by light. Citric acid is more stable.
Try making your own and keeping it in the refrigerator- I can't recommend making sun tea for obvious reasons (botulism). I never had a problem, nor did any of my friends to the best of my knowledge, but it has been reported in the literature.