A ‘natural yeast’ fermentation (or ‘wild yeast’) is about letting the existing yeasts from the fruit or the atmosphere populate the sugars in wine or cider. Naturally, (pun intended) you would not add chemicals to a natural/ wild yeast fermentation because you want the continuation of bacteria between fruit and juice (no juice sterilization.)
The opposite of a natural yeast fermentation is a cultivated yeast fermentation (although cultivated yeasts are quite natural too.) This is when you select yeast strains to dominate the fermentation. Levels of chemical sterilization may range, but the difference boils down to who’s selecting the yeasts. Wild is the opposite of cultivated, and ‘natural selection’ is the opposite of manipulated selection (notice “man” in that word.) So, a natural/ wild yeast fermentation is about man NOT selecting the yeast stain (which is a fact of choice these days in the modern world.) It’s important to remember that.
In Cider 101 they touch on this subject: ‘cultivated yeasts’ –vs- ‘wild yeasts’. Your teachers will mention that in France, England and Spain there are cider-makers still using wild yeasts to ferment, but here in America almost everyone uses cultivated yeast strains because we know that’s the surest way to achieve a safe and tasty fermentation. What your Cider 101 teacher unwittingly infers (before moving on and never again mentioning natural fermentation again) is that ‘natural cider’ is the result of ‘natural yeast fermentation.’ This misinformation, it turns out, is the greatest blind spot in cider today. Because this partial truth is so widely accepted, this little bit of misinformation allows cider companies to exploit ‘natural fermentation’ to make it seem that they have a ‘natural cider’ when they most definitely do not.
Natural cider is infinitely more complex than a natural fermentation. Natural cider starts before the juice, before the apples are picked, before the spring blossom, before the “growing years”, and even before the trees take root in the ground. Natural cider has it’s roots (yes, pun intended) in (1) the soil, and (2) the seed. This is where it all begins, and it is absolutely imperative the natural cider drinker be aware of these origins. But because we are so focused on the end product (a great drink!) we tend to work backwards. Working backwards, we are bound to get hung-up somewhere. Currently, the conversation (and marketing) over “natural wine or cider” is hung-up at the fermentation stage.
Working-backwards you are going to run into this hypocrisy…
Natural Cider is the result of what happens naturally. We are not trying to ‘achieve’ natural cider, we are trying to discover it. It’s about allowing the drink to happen. If you control the gene selection by way of choosing select cultivars (like pinot noir or golden delicious), and you chose where the apples were grown and how they are grown, then nature isn’t really a dominant factor anymore. It's man's domination. So why trumpet the fact you use ‘wild yeasts’ to ferment the juice when the fruit you use is (A) selected (and cloned,) and (B) cultivated in a manipulated agricultural settings? Everything that lead up to the fruit was cultivated so why start now? Do you get what I’m saying? You don’t start with hygiene and then let a little nature happen. At the VERY minimum, at least use organic fruit!