The addition of sulphites in drink products are not particulaly well advertised and the cold hard facts of this additive (ie how much has been used) is sometimes unclear.
Many ciders and most wines contain sulphites /sulphur dioxide. It may be the case that you have never had a ‘pure’ cider or wine at all!
Sulphites are used in order to kill the natural yeast that is naturally present in apple juice. An added yeast that has been cultured is then used to create a more standardised product and reduces the risk of spoilage and waste for the producer.
Read the full article at the Mahorall Farm cider web site