How can you culture yogurt without heating, stirring or electricity?
Yogurt-forming bacteria still ferment milk even without being warmed, just not so quickly. In order to make yogurt the traditional way (see previous section) the starter culture must be stirred into the milk to make sure it is thoroughly mixed in. Unfortunately, this also raises the oxygen level and destroys the natural growth pattern, both of which are at the least, unhelpful. In Dynamic Fermentation milk passes through a narrow tube lined with yogurt-forming bacteria, which achieves the same result as stirring but without the negative effects of stirring.
With no need for either heating or stirring there is no need for electricity.
How is it possible to make yogurt without starter culture?
The reason for the priming operation (see here) is to install a thin layer of yogurt-forming bacteria on the inner wall of the tube (resident bacterial culture’). In Dynamic Fermentation, fermentation starts when milk is poured into the (primed) tube; the presence of milk stimulates the bacteria which start to multiply rapidly and colonise the milk; since yogurt-forming bacteria are already present and oxygen is largely absent, fermentation starts with no need for a starter culture.
The resident bacteria in the tube form a stable culture which also excludes other bacteria by making conditions inside the tube too acid for them to survive. In this and other ways Dynamic Fermentation ‘designs out’ many of the problems that arise with traditional yogurt making, at the same time producing yogurt that is almost entirely composed of young bacteria with a very high ‘live’ count (some commercially-produced ‘live’ yogurts add the live culture as the final stage in processing).
Is it safe to consume yogurt produced by Dynamic Fermentation?
The issue of safety has not been taken for granted however and an extended trial (with the author as guinea pig) was completed in July 2018 following a 12 month trial consuming yogurt produced by Dynamic Fermentation on a daily basis; the result was positive with no evidence of risk to personal health and well-being. However, anyone suffering from soya-intolerance or a precarious state of health should follow medical advice.
Why is there no sterilisation of equipment in Dynamic Fementation
Sterilising equipment in between batches of milk is a way of dealing with contamination in traditional yogurt making. This is usually an imported problem brought from outside or arising from exposure to air. In short Dynamic Fermentation employs/exploits a combination of strategies to eliminate contamination including:
permanently excluding air
an acid environment, brought about by the bacteria themselves
ensuring that milk flows smoothly (‘laminar flow’) through the equipment
The restriction to non-dairy milk eliminates many of the problems with traditional fermentation. Any attempt to sterilise equipment in Dynamic Fermentation however would at the very least undermine the contamination-reducing steps outlined in the bullet points and probably introduce greater problems due to variations in procedure and/or handling.
How reliable is the process of Dynamic Fermentation?
Experience gained using the ‘In Vitro’ model (see below) over a year and more has so far been impressive, both in terms of never-failing output and quality, with operation continuing through the depths of winter and the (very) hot summer that followed. Even neglect for a week seems to have only a minor effect on Dynamic Fermentation; the worst outcome so far following the period of neglect was a slow-moving ferment flow from the spigot when harvesting; in this case the flow took some time to start.
I have a family of four boys (making us six in total). Is there any way I could arrange a suitable supply from Dynamic Fermentation for us all?
Well, two options spring to mind (use your imagination and I’m sure you can come up with more!). If you have the time you could use the model as shown in ‘Image 2’ (see ‘Introduction’) to run several batches a day which should provide sufficient yogurt curd (wait till you have completed fermentation then strain the entire run together). Alternatively, use a larger container to run a scaled-up version. The largest yet constructed was built from a disused 30 litre cylindrical perspex aquarium; this has the capacity to produce several times the output of the fermenter shown in Image 2 – but be warned – these don’t come cheap if you buy new! (around £130 a piece from ‘BiOrb’)
Once you start do you have to keep re-filling every day?
No. I have left a gap of days (sometimes almost a week) before re-filling. Since there is no air, the raw yogurt is very stable inside the gallery.
How long does the yogurt produced by ‘Dynamic Fermentation’ (DF) last?
It is always useful to place recently harvested yogurt in a clean pot which is labelled to show the date. Kept in a fridge the yogurt loses its pre-eminent taste within a day though the product is still very palatable for a few days. However, unless allowed to warm, the coldness taken straight from the fridge anaesthetises taste buds so the taste sensation is to some extent suppresed. Quality is best if removed from the fridge half an hour or so before consuming.
What is ‘Live’ yogurt?
This means, ‘Contains live bacterial cultures’. Some unscrupulous manufacturers use misleading phrases like ‘Made using live bacterial cultures’ though it would not generally be possible to make yogurt by any other route. ‘Live’ foods have become a major feature for vegans – this may sound strange but it really means no more than live plants (eg bean sprouts) or bacteria, as here.
Are timings and other measurements absolutely critical in ‘Dynamic Fermentation?
– No; part of the beauty of DF is that it is very forgiving and generally allows a wide margin of error.
Isn’t ‘Dynamic Fermentation’ a threat to health unless you kill the bacteria in milk by heating?
– Heating is a necessary first step when using DAIRY milk because of all the ingredients, some of which could cause problems unless dealt with by heating. Non-dairy milk is different because by law it must only contain those ingredients listed on the label, none of which represent a threat to health in the case of organic non-dairy milk.
Is ‘yogurt’ the same as ‘yoghurt’ ?
– Absolutely; the spelling varies.
Is fermentation for making alcohol the same as that for making yogurt?
– No; brewing requires yeast (a fungus) whereas yogurt is made by bacteria. There are other significant differences too.
How do I know if there is a problem or something isn’t going right?
– This is called ‘Quality Control’ and is best managed by visual inspection and use of your sense of smell. If something is not going right these are probably the most sensitive tools at your disposal.
What should the fermented milk look like as it comes out of the spigot?
– Same colour as the milk, consistency between hot custard and porridge. It should also have a faint but persistent odour of toffee.
Is the yogurt produced this way different from other live yogurt?
– Yogurt produced in your home (consumed directly after straining) is a lot fresher than any yogurt you buy in a shop plus it should have a much higher content of live bacterial culture; in other words it is reasonable to expect that it is healthier – plus, consumed fresh it has a richer, fuller taste.
What is the expected lifetime for a ‘Dynamic Fermenter’?
– At present this is open to speculation but as there is only one permanent moving part (the lever part of the spigot), a lifetime of at least 5 years seems reasonable.
Is ‘Dynamic Fermented’ yogurt safe for kids/pregnant women?
– Providing there is ‘Good practice in the kitchen’ (click here), unless you have medical advice to the contrary (e.g. soya intolerance), there are no reports of additional grounds for concern with consuming non-dairy yogurt (see views). Professional clinical advice is currently lacking though NICE makes a general comment on yogurt here.
Why not use a wider bore grade of tubing for the gallery?
– This is an interesting one (the argument in favour being that it should increase yield) but cannot be answered fully without an understanding of the ‘surface area to volume ratio’. If interested, why not give it a try anyway?
What if I have to be away for a few days?
In general there shouldn’t be a problem for up to three or four days absence except in very hot weather. Absence beyond this brief period may also be OK though you are probably better off to:
- plug the upper end of the tube with a well-fitting stopper (cork bungs best)
- lay the ‘Dynamic Fermenter’ horizontally on your knees
- gently easing the tube off and away from the spigot, keeping the lower end of the tube higher than the plugged end
- carefully ease the tube off and away from the spigot removing the entire tube with one hand from the drinks dispenser
- plug the bottom end securely.
- Coil the tube and keep in a cool place or fridge till your return.
On you return the procedure is pretty much the same in reverse order though you may need to repeat the beeswax dressing of the spigot before re-attaching the lower end of the tube.
What about using other containers instead of a drinks dispenser? – Alternatives tried prior to the pilot project included:
- A discarded cartridge from a water cooler,
- A collapsible 15 litre folding water carrier from a camping shop.
- A 15 litre transparent plastic bucket and lid
- A 30 litre perspex cylindrical aquarium
With the exception of the last on the list of possible alternatives these are all considerably cheaper than most drinks dispensers (while possibly lacking the ornamental appeal) though a clean, food grade 15mm plastic or metal spigot (available online) needs to be found and fitted in each case.