I would like to know if it would be safe to substitute fresh or bottled apple "cider" in place of apple juice in a safe tested jelly recipe that only mentions apple juice. I am finding contradictory information, that the cider may increase acidity and therefore could not be considered a safe substitution. It has been my experience that substitutes are safe, especially in jam/jelly, as long as the acidity of the ingredient remains the same, or is a higher acidity than the original. Is this not the case?
If this is not a safe substitute, can you please expand on why?