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Assume that we have a plant, e.g. kale, which is prone to amylolysis if not harvested during a frost period.

If it is harvested and put in a household freezer, such that it is frozen solid slowly enough for cell walls to burst, will the amylolysis stop, or will it still occur? Will it occur if it is kept in a fridge in the 0-4 Celsius range? If it does not occur while the vegetable is frozen, will it start after thawing?

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  • $\begingroup$ I think it will be at least delayed. Enzymes habe an optimal temperature at which they work best. I don't know this for this special amylose, but at 0°C it will definitely be much slower. The rate of the enzyme will not be zero though... $\endgroup$ – Chris Dec 20 '13 at 8:06
  • $\begingroup$ @Chris interesting. I thought that maybe my question is too silly to ask, and half expected to get an answer saying "once the cell plasma is frozen, all biological processes cease because enzymes, hormones etc. can't move around". $\endgroup$ – rumtscho Dec 20 '13 at 10:20
  • $\begingroup$ I was thinking about 0°C, not freezing. When you freeze the plants, the enzymes will be not functional. The backside is that you probably break cells with the freezing and set free the enzymes. $\endgroup$ – Chris Dec 20 '13 at 10:24
  • $\begingroup$ @Chris what do you mean by "set free the enzymes"? Does this mean that they will start converting the starch upon thawing independent of ambient temperature, because they are free now? I am afraid my mental model of the whole process is very incomplete. You will certainly break cell walls, this is very noticeable with thawed vegetables. $\endgroup$ – rumtscho Dec 20 '13 at 11:21
  • $\begingroup$ With "set free" I mean that the enzymes can work not only inside the cell but also outside, since the interiour of the broken cells is set free. This is especially a problem when you work with lysed cells and protein degrading enzymes. Its probably no problem here. $\endgroup$ – Chris Dec 20 '13 at 13:05
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Yes. Freezing would practically stop all biochemical reactions. Household freezer can maintain -15⁰C so that would work. However, freezing also damages the cells if cryoprotectants are not used. But I guess that is not your concern.

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