Different bacteria, yeasts and molds prefer different fermentation temperatures so different type of fermented food, kombucha, yoghurt, sauerkraut etc prefer different temperatures too..
That being said around 21°C or 70°F is a middle range temperature that suits many types of fermentation.
But don’t worry if where you live does not have an eternal spring – fermentation is surprisingly flexible.
Warming ferments up is actually quite easy you can purchase very inexpensive small temperature controlled mats quite easily on the internet.
Cooling ferments down is quite easy – nearly everyone owns a fridge and ferments will continue even in your fridge just at a much slower pace. If you leave them a long time in your fridge fermented food will get very very sour!
Vegetable and Dairy fermentation
Broadly speaking you get better flavours at lower temperatures for many type of vegetable and dairy fermentation with around 21°C being the optimum.
Temperature Guide
| Farenheit | Centigrade | |
| Yoghurt | 112°F | 45°C |
| Tempeh | 86°F | 30°C |
| Kefir | 70°F | 21°C |
| Kombucha | 70°F | 21°C |
| Sauerkraut (or any veg.) | 70°F | 21°C |
| Miso | 70°F | 21°C |
| Kimchi | 39°F | 4°C |
| Vinegar | 86°F | 30°C |
These are the ideal temperatures – a temperature of + or – 10°C or 50°F is probably still going to work in most cases (Note: the warmer loving fermentations really don’t like being cold).
Anymore than that and you might be pushing your luck and get so so flavour profiles.
Most lacto vegetable fermentations can work quite will in your fridge but 7 days at 21°C is equivalent to about 7 weeks at 4°C (fridge temperature).
The top and middle shelves of your fridge are the warmest parts and therefore often a good place if you are trying to ferment food in your fridge.