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Asked by kylemarrs6321 ·February 19, 2021 ·15.4k readers

FPJ, temperature at gathering

With FPJ, will the temperature in the morning effect the quality of material that is ultimately produced? Is it ok to gather material in the 40s or 50s degree range? I know microorganisms are most active at warmer temperatures. Any thoughts?

fermented-plant-juice temperatures

Top answer

Drake Weinert Foundation · Feb 24, 2021
short answer: no. 40-50s is fine. longer answer: the best time to gather material is in spring. based on where you are, it can be quite chilly in the morning, but this should not have a drastic effect on the fermented plant juice. remember, these recipes come from japan and korea, where it is quite cold, so you will be fine. temperature does however have a more drastic effect on supersaturation, and more sugar should be added.

From the KNF library

From the KNF library Drafted by Claude from Office Hours and the books · Sep 2026 · 4 sources

The library sets no temperature for gathering. It does say what to watch instead.

  • Gather before sunrise, while plants are in respiration mode, not photosynthetic mode. (Student's Manual, Basic Course, p. 32)
  • Avoid rain. Ideally wait two sunny days after it stops. (Student's Manual, Basic Course, p. 32)
  • Do not rinse. Surface microbes carry out the fermentation, and too few means poor fermentation or low yield. (Student's Manual, Basic Course, p. 32)

Drake's manual says sunrise is the best time to gather the plant's vitality, but you do not have to hit it exactly. (Pure KNF Manual, p. 38)

Cool weather affects the ferment after gathering, not the gathering itself. Cool or cold periods slow fermentation. (Student's Manual, Basic Course, p. 34) Warmer air speeds it up, so batches run 3 to 14 days depending on temperature. (KNF Demystified, p. 33)

The sources differ on timing. One says fermentation ideally takes no more than 7 days, because quality appears to diminish after that. (Student's Manual, Basic Course, p. 34) Another allows up to 14. (KNF Demystified, p. 33)

Sources

  • p. 34 Student's Manual, Basic Course · “the quality of FPJ appears to diminish thereafter”
  • p. 38 Pure KNF Manual · “Do I have to gather the growing tips right at sunrise? No. This is the best time to gather the vitality of the plant.”
  • p. 33 KNF Demystified · “ferment for 3~14 days depending on temperature (the warmer the air, the quicker the ferment)”
  • p. 32 Student's Manual, Basic Course · “Plant parts should be harvested while the plants are in respiration mode”

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