How long can LAB last in fridge - without sugar mixed in?
Top answer
From the KNF library
The library gives different numbers for unsugared LAB in the fridge. Most answers say about a month. (Office Hours Ep. 12, 31:40) (Office Hours Ep. 7, 54:49) (Office Hours Apr 2026, 31:35) Cold slows LAB down but does not preserve it. (Office Hours Apr 2026, 31:35) One answer says use it within a month or two. (Office Hours Ep. 77, 1:13:27) Another says a few months. (Office Hours Apr 2025, 39:27) The UH student manual says refrigerated LAB keeps six months. (Student's Manual, Basic Course, p. 15)
To check a jar, use your nose. Good LAB smells sweet. If the smell turns rotten, discard it and make a new batch. (Student's Manual, Basic Course, p. 15) Drake says the same: if it smells bad, don't use it. (Office Hours Ep. 45, 48:37)
For longer storage, Drake recommends mixing in equal volumes of brown sugar. One liter of LAB takes one liter of sugar. (Pure KNF Manual, p. 80) The sugar ties up the water, so the microbes go dormant instead of fermenting on. (Pure KNF Manual, p. 80) Keep the temperature steady. (Office Hours Ep. 44, 15:15)
The library does not cover microscope counts or a taste test.
Sources
- 31:40 Office Hours Ep. 12 (Dec 2021) — Desert IMO Collection, Lawn Biochar, WCA Bone Ratios · “LAB lasts about a month unsupersaturated, up to three months or more if supersaturated.”
- 1:13:27 Office Hours Ep. 77 (May 2023) — Coffee Leaf Rust, Seawater Minerals, and 327 Miles of Roots · “use it within a month or two and keep making small fresh batches”
- 39:27 Office Hours (Apr 2025) — Vortex Compost Tea Brewers, LAB Shelf Life, Taro Leaf Solution · “unstabilized LAB only lasts a few months in the fridge and a few weeks without one”
- 54:49 Office Hours Ep. 7 (Nov 2021) — Fermented Seawater, Brown Rice Vinegar, Fish Amino Acid · “About one month is safe; after that the rod-shaped bacteria start to decline unless you super-saturate it with sugar.”
- 48:37 Office Hours Ep. 45 (Aug 2022) — Pig Feed From Dairy Waste, IMO Collection, Water-Soluble Calcium · “trust your nose, if it smells bad, don't use it”
- 15:15 Office Hours Ep. 44 (Aug 2022) — LAB Troubleshooting, Bacillus Subtilis Probiotics, Fish Amino Acid · “Mix in equal parts sugar by volume and keep the storage temperature steady, not swinging up and down.”
- 31:35 Office Hours (Apr 2026) — LAB Preservation, Acidic Soil pH, and BMW Crystal Brewers · “cold just slows it down rather than preserving it, so use unsaturated LAB within a month”
- p. 15 Student's Manual, Basic Course · “LAB culture may be kept refrigerated for 6 months”
- p. 80 Pure KNF Manual · “PurePolice will require equal volumes of brown sugar, so 1 liter of solution will need 1 liter of brown sugar.”
Also discussed on Office Hours
Desert IMO Collection, Lawn Biochar, WCA Bone Ratios
- 31:59 …refrigerator, how long can comfrey FPJ and lab be used if not super saturated? I live in zone seven…
- 32:14 …they will last many months because there's already sugar in there. In the case of the LAB,…
- 32:52 …the fridge, it's about a month. It can last longer than that, but you have a diminishing return,…