Clarification is traditionally done by Keeving. Some say that this is where you – to some degree – make the cider. Pectin is de-esterified by pectin methyl esterase (PME) enzymes and this allows the pectin to form a gel when calcium ions are present. Both pectin, PME and calcium ions are natural occurring in apple must. However in some modern cider production they are added to ensure the gel formation. In my experiments I added both PME as NovoShape ® and calcium chloride.
Why is Keeving important?
Impurities are entrapped in the gel and the wine is therefore clarified. But Keeving is more than this. Beside impurities the pectin gel entrap important nutrient. When nutrients are removed from the must fermentation will naturally stop (or slow down) and leave a wine with a natural sweetness. So Keeving is also a way to control fermentation.
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