Propagating a sourdough culture without a fridge in the tropics

The refrigerator can help in storing and maintaining a sourdough culture. The low temperature helps to slow down the activity in the culture and promote the production of acetic acids.

But what if there is no refrigerator? And what if you live in the tropics with a constant ambient temperaure of around 30C?

A sourdough culture can be maintained under these conditions by regularly feeding it e.g. three times a day (i.e. on 8 hour intervals) or four times per day (i.e. on 6 hour intervals). Over a period of time (days, weeks, or longer) the sourdough culture may not ferment too much; the culture may not get too sour with too little yeast activity.
What if you have to fit the feeding schedule with other commitments? Is a feeding schedule of two times a day (e.g. at 7 PM and at 7 AM) feasible?

Here it is tested for a week. At every feeding a stiff starter is made since this provides a more stable environment for the culture. After each period of 12 hours the culture must have at least tripled in volume and may not have collapsed. No salt is used to control the yeast and no starter is thrown away.

Day 1

Feeding schedule
  1. Feeding at 7 PM of the previous day: 2.5 gram sourdough culture is mixed and kneaded with 8 gram water and 16 gram flour into a stiff dough and fermented for 12 hours at room temperature. Result: 26 gram of sourdough culture.
  2. Feeding at 7 AM: The 26 gram of sourdough culture is kneaded with 75 gram of water and 150 gram flour and fermented for 12 hours at room temperature. Result: around 250 gram of sourdough culture.
  3. 2 gram of the culture is retained for a new starter and the rest is used for a bread.
Note that the inocculation is only about 10% at each step. If the fermentation is too fast, the inocculation can be reduced. If the fermentation is too slow, the inocculation can be increased.

Photos
  1. Starter at 7 AM and at 7 PM.
  2. Bread dough after fermentation
  3. Baked bread 1 and 2.
Observations Although the sourdough culture had quadrupled, it was too sour. As a result the bread dough ruptured. To slow down the fermentation an inocculation of 5% will be attempted. Additionally only 175 gram of starter wil be made instead of 250 gram.

Day 2

Feeding schedule
  1. Feeding at 7 PM of day 1: 2.5 gram sourdough culture is mixed and kneaded with 8 gram water and 16 gram flour into a stiff dough and fermented for 12 hours at room temperature. Result: 26 gram of sourdough culture.
  2. Feeding at 7 AM: 8 gram of sourdough culture is kneaded with 56 gram of water and 111 gram flour and fermented for 12 hours at room temperature. Result: around 175 gram of sourdough culture.
  3. 1 gram of the culture is retained for a new starter and the rest is used for a bread.
Photos
  1. Starter at 7 PM
  2. Baked bread 1
Observations This time the starter was alright.

Day 3

Feeding schedule
  1. Feeding at 7 PM of day 2: 1 gram sourdough culture is mixed and kneaded with 3 gram water and 6 gram flour into a stiff dough and fermented for 12 hours at room temperature. Result: 10 gram of sourdough culture.
  2. Feeding at 7 AM: 10 gram of sourdough culture is kneaded with 55 gram of water and 110 gram flour and fermented for 12 hours at room temperature. Result: around 175 gram of sourdough culture.
  3. 1 gram of the culture is retained for a new starter and the rest is used for a bread.
Photos
  1. Starter at 7 PM.
  2. Baked bread 1
Observations The starter was too sour.

Day 4

Feeding schedule Same as day 3
Photos
  1. Start with 1 gram. Starter at 7 PM.
  2. Baked bread 1
Observations This time the starter was alright.

Day 5

Feeding schedule Same as day 3
Photos
  1. Fermented starter of 175 gram.
  2. New start with about 1 gram (less than 1/8 teaspoon): 1 and 2 (scale is in centimeter).
  3. Baked bread 1
Observations The starter was started with about 12 gram sourdough culture. This was too much and the fermentation was completed in less than 6 hours. I could let the starter ferment further for another 4-6 hours, but decided not to do so and restarted on about 1 gram. The amount of sourdough culture at the second feeding thus should be less than 10 gram. 6-8 gram should suffice.

Day 6

Feeding schedule
  1. Feeding at 2 PM of day 5: 1 gram sourdough culture is mixed and kneaded with 3 gram water and 6 gram flour into a stiff dough and fermented for 12 hours at room temperature. Result: 10 gram of sourdough culture.
  2. Feeding at 12 AM: 8 gram of sourdough culture is kneaded with 55 gram of water and 110 gram flour and fermented for 12 hours at room temperature. Result: around 175 gram of sourdough culture.
  3. 1 gram of the culture is retained for a new starter and the rest is used for a bread.
Photos
  1. Starter at 10 AM: 1 and 2.
  2. Baked bread 1
Observations

Day 7

Feeding schedule Feeding at 10 AM of day 6: 0.5 gram sourdough culture is mixed and kneaded with 58 gram water and 116 gram flour into a stiff dough and fermented for 24 hours at room temperature. Result: 175 gram of sourdough culture.
Photos
  1. Measuring 2.5 gram: 1.
  2. Stretching it out: 2.
  3. Measuring a fifth i.e. 0.5 gram: 3.
  4. Fermented starter after 14 hours: 4.
  5. Fermented starter after 24 hours: 5.
  6. Baked bread 6
Observations This was a first attempt to propagate a starter with a single feeding per 24 hours. The starter had fermented too far and had become quite sticky. An amount of 0.25-0.40 gram should be enough. To be continued in another experiment.

Conclusions

It is feasible to propagate a starter with two feedings per day i.e. at 12 hour intervals.
To obtain about 175 gram of starter after 24 hours, the first starter is prepared with 0.25-0.5 gram sourdough culture, 3 gram water and 6 gram flour.
After 12 hours 8 gram of the fermented starter is kneaded with 56 gram water and 112 gram flour. After another 12 hours about 175 gram of starter is ready to be used. A small amount is pinched off to propagate the culture further and the rest is used for baking bread.