The move from dairy to plant milk represents a major change to the fermentation process, with the elimination of any need for heating the milk before fermentation – a significant simplification in itself. However, equipment and routine must also be considered –
Equipment- Design of the fermentation chamber
Routine: This must solve the problems of how to:
– get the starter mixed into milk
– Increase visibility of the ferment (without increasing the exposed surface of the ferment)
– Reduce/eliminate the need for extraction and storage of starter
Ideally, starter culture would remain within the fermentation chamber (surrounded by whey) and fermented milk would be the only item that moves.
Finally, ‘shutdown’ for cleaning/storage of equipment needs to be replaced with a less disruptive process.
Practical Alternatives to the bowl
The list of problems on the previous page look challenging, but after more than 7 years testing and reviewing 4 possible alternatives to a bowl, the ‘Open-ended Tube’ option was the clear winner.
Fermentation in an open-ended tube
Semi-rigid plastic tube offers a relatively cheap, robust and safe option, of which the ‘food grade’ variety is clearly best.
If both ends of the tube are firmly clamped in position with one end higher than the other, filling and harvesting operations become a lot easier. Be sure to choose tubing that is compatible with the funnel and spigot in term of size. All three components are available online. New items often carry manufacturers advice on cleaning before first use.
Funnel
Spigot
Design considerations for Line Fermentation
For practical reasons, fermenting in an open-ended tube needs to solve issues like:
- How to hold either end of the tube firmly in position
- How to fill the tube
- How to remove fermented milk from the tube
- How to keep either ends of the tube clean
How does milk get started in a tube?
The first batch must be started in the usual way before adding to the tube. Subsequent batches are self-starting without assistance.
Each fresh batch of milk flushes out maybe 97% of the previous batch of fermented milk from the tube, leaving just enough culture to restart fermentation in the next batch of milk as it arrives.
After re-filling, the funnel at the top end of the tube is promptly replaced with a dust cap, and fermentation re-starts with almost no ferment surface exposed to air, with the result that the risk of contamination is reduced to close to zero.
The arrangement has been named ‘Line fermentation’ to avoid the ambiguity of ‘tube fermentation’.
Guidance on building a line fermenter will soon be available as a free download to members of VYM.
More details, including some of the benefits of line fermentation are included in the supplement to the website, ‘Section F’.
Model Linear Fermenters
The model designs that appear below produced yogurt for the table over a period of months, during this time each produced around several litres of prime quality yogurt.
Each model represents an advance over previous models, while operation and maintenance remained unchanged.
The pendulum model (with tube clamped perpendicularly)
A modified drinks dispenser
Modified household bucket with transparent walls
Modified 37L perspex aquariums (Plants for decoration only)
A guide to the construction and maintenance of all the models shown is available, free to VYM members as a download.