Alternatives to the bowl for fermentation
The move to plant milk represents a major change that also eliminates the need for heating before fermentation; also in need of consideration however are –
Equipment : In particular, the design of the fermentation chamber
Routine: outstanding problems including 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
“A summary of the problems so far” identifies challenges for improving the 5-stage process. However, after more than seven years considering and testing potential alternatives for fermentation (including a bottle, an archimedes screw, a bioreactor and a length of open-ended tube) the last-named emerged as the clear winner in terms of simplicity and maintenance.
Fermentation in an open-ended tube
Semi-rigid plastic tube offers a relatively cheap, robust and safe option, and ‘food grade’ tubing is available. 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. Tubing must be compatible with the funnel and spigot; all three components are available online. New items often carry manufacturers advice on treatment before first use.
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 though each of these is easily overcome with forethought and care
How does milk get started in a tube?
The first batch must be started in the usual way before adding to the tube (see Stage 1). 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’ (tubes can be uniform bore or tapered and with or without branches; permeable or impermeable).
Guidance on building a line fermenter is 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, also available as a free download to members of VYM.
Model Linear Fermenters
The model designs that appear below produced Prime quality yogurt for the table over a period of months, during this time each produced around several litres of prime quality yogurt over a period of weeks or occasionally months.
Each model represented an advance over previous models, while operation and maintenance remained unchanged.
A guide to the construction and maintenance of all the models shown is available, free to VYM members as a download on the Facebook page or by e-mailing VYM at veganyogurtmakers@icloud.com.