Kill the Yeast

January 28, 2010

In my last post, I said in order to obtain a sweet cider, the yeast needs to be killed to prevent it from eating any more sugar. There are several ways to do this, including the use of potassium sorbate or pasteurizing.

I have stressed that when picking out sources to make wine and cider from that it needs to be preservative free because the preservatives will prevent the yeast from fermenting. Now, when the yeast is towards the end of fermentation, preservatives in the form of potassium sorbate help kill the yeast to stop fermentation.

If you don’t want to add chemicals, the other option to kill the yeast is by pasteurizing. Andrew Lea describes the process as follows: “The sweetened bottled cider can then be batch pasteurised on a domestic scale in tanks of hot water e.g. at 68o C for 20 minutes, although it is much more efficient to use a proper flow-through heat exchanger operating at 90o C with a residence time of 30 seconds so that the pasteurised cider is filled directly into warmed bottles. Equipment of this sort does not come cheap and can usually only be justified in the context of a commercial operation.”

In Cider: Hard and Sweet, Ben Watson recommends having a mixture that reads 1.010 on a hydrometer, bottling it, and then possibly waiting a few days before pasteurizing. With “a large kettle on the stovetop, or in a metal tub or livestock trough that’s set over a propane burner outdoors, place the capped bottles in the water bath; the water should come up to the fill line on the necks. Fill one bottle with water that’s at about the same temperature or cooler than the cider, and leave it uncapped, with a thermometer inserted into it. Heat the water in the tub or kettle until the thermometer in the test bottle reads 150⁰F (65⁰C) for 10 to 20 minutes… The bottles may start leaking gas around their caps and hissing; this is fine and isn’t cause for concern. Remove the bottles carefully and cool them slowly to minimize any risk of breakage.”


2 Responses to “Kill the Yeast”

  1. The Mad Pope Says:

    Does this kill carbonation, or is carbonation intact?

    • You know, I’m still learning, so I see I need to correct myself. Sorbate does not kill yeast – it prevents it from reproducing. At the end of fermenting, sorbate can be added and then the batch can be sweetened without fear of the yeast eating it.

      Now to The Mad Pope’s question… sorbate would not allow for carbonation. Pasteurizing can be done after bottling and adding sugar for carbonation, after enough time has gone by for carbonation but not enough time that the building pressure might be dangerous. Oddly, wine and mead makers are busy trying to figure out ways to “degas” or remove gas, while beer and cider makers are trying to figure out how to add it.

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