Injera (update #7 - [as of 7/30/22] includes modified batter formulation and a few process tweaks)
Since this is a process of discovery more than an exposition of well understood science, the update number in the title will change when enough significant changes have accumulated that you might want to re-read from the top. At some point it will stabilize but in the beginning it is somewhat volatile as I discover/uncover truth and apply a dope slap for what proves to be erroneous.
The time has come to see if I can make an acceptable injera at home. I found a few injera-related posts here on TFL though while I found them interesting (and one provided a compact summary of an excellent YouTube video) none seemed to improve on what I found on YouTube and in some quite excellent reference sources.
Having watched a number of videos explain how to make injera, I found some common threads which I have tried to interpret using my general understanding and knowledge of other fermented foods (mostly sourdough and idli/dosa). I present here my evolving observations which are open for discussion and prone to elaboration, enhancement, and correction based on superior knowledge from other members of this community:
An outstanding publication on Ethiopian fermented food containing a fairly complete section on injera
[1]Ethiop. J. Biol. Sci., 5(2): 189-2245, 2006 [section on injera begins on page 205]
Annotated injera flow chart from linked paper:
It appears that an injera starter culture contains multiple yeasts and multiple LAB, though it is not clear to what extent there is a progression of activity from one yeast and LAB to others over the course of a typical fermentation cycle.
The pouring off of the liquid layer that accumulates on the surface of injera starter and batter is essential, and discarding the liquid layer results in loss of soluble compounds (amino acids, sugars and minerals) and a large portion of the microorganisms. It seems that one function served by the liquid layer on the surface is to keep mold and aerobic yeast off of the batter. I found that after a few days a layer of aerobic yeast forms on the surface of the ersho, and mold will eventually begin to grow on any bits of batter that remain on the side of the fermentation container. Thus washing the sides of the container before you begin the fermentation is an act of sanitation and contamination reduction while pouring off the ersho gets rid of the aerobic yeast that tends to accumulate there. As a result of experimentation I have discovered that if you run the fermentation near the optimum/elevated temperature (37°C/99°F) the aerobic yeast and mold never show up, perhaps because the cycle is so short. They may be there but not at levels sufficient to cause a problem.
The use of self-rising flour (apparently an adaptation of the Ethiopian method and now commonly used in NA) seems to be a way to get by with a less than fully active starter, letting the baking powder in the self-rising flour serve as an alternate source of CO2 to produce "eyes" in the final fried injera. Another possibility is that the microflora in injera are incompatible with wheat flour, or wheat flour will not ferment quickly enough to generate the required CO2 and an alternative is to use baking powder. There is no evidence that the resulting injera are of lower quality in any way. In fact, in many parts of Ethiopa (and in NA) grains other than teff are used to make injera, including sorghum, millet, wheat, barley, and corn (maize).
I found a paper that used modern PCR methods to characterize the yeasts in injera batter and there were clear differences in the constituent yeasts between injera batters prepared at home, in hotels, and by what were characterized as microenterprises (which I presume means that they were producing commercial injera).
Pichia fermentans was the only yeast that was found in all 97 of the injera batter samples (which may indicate that it is brought to the mix by the teff flour itself); and our old friend Saccharomyces cerevisiae was also found in all of the batters prepared in hotel kitchens (though it does not speculate as to whether the source was intentional addition or cross contamination from other yeast-based products being produced in the hotel kitchen). This may indicate that any yeast that will tolerate the low pH conditions of the injera batter is sufficient to produce the CO2 needed to make "eyes" (bubbles) in the resulting injera (or not if baking powder is needed to provide additional CO2).
A final warm fermentation followed by cooling the batter may be just a retardation step that drops the temperature of the batter and allows any additional CO2 (being produced in the batter) to be absorbed into the liquid phase, but the guidance to use the batter when the secondary fermentation peaks (I assume that means that the height of the batter in the fermentation container peaks) is consistent with frying when the CO2 in the batter is maximized. The CO2 then comes out of solution when the batter heats up on the mitad (frying surface) and makes the "eyes" as the bubbles are called. The size of the eyes seems to depend on the viscosity of the batter with a thicker batter producing larger eyes, and a thicker/less desirable injera.
Covering the injera for a period at the end of the cooking cycle keeps the surface from completely drying out by retaining moisture from condensed steam on the surface of the injera while allowing the dough to fully cook and solidify.
It is clearly not essential to mix injera batter by hand and any mixing method that fully hydrates the flour(s) and eliminates lumps is adequate. I found no obvious reason not to use a whisk, blender, or simply a spoon.
In some of the YouTube videos there is a step where the batter is put into a blender and blended for perhaps 10 seconds to eliminate the "sandy texture" of the batter. I haven't figured out what this is about. The boiling of some batter with water for a couple of minutes to make the 'absit' which seems very similar to making a tangzhong (water roux) is claimed to have the same effect of smoothing out the batter texture. I found another video where the batter was blended after incorporation of the self rising flour to get rid of lumps.
To test the hypothesis that absit is just a tangzhong, I mixed 50g of brown teff flour with 250g of RO filtered water and heated it to 65°C/149°F while stirring, as I would do to make a tangzhong. The behavior was exactly as expected, the mixture thickened and stirring with a whisk was sufficient to see the bottom of the pan so the starch in the teff is gelatinized at about the same temperature as wheat flour. A search for gelatinization temperatures confirmed that teff gelatinizes at 145–176°F (63–80°C), a few degrees above wheat [124–140°F (51–60°C)].
I am struck by the similarity of the injera process to making dosa, where the final batter viscosity is set by the need to spread it suitably on the frying surface and depends on many factors which make it difficult if not impossible to predict exactly how much additional water will be needed. The acceptable band of viscosities is quite narrow and when it is too low the injera produces fewer eyes and large cracks form between isolated islands of cooked dough. If the viscosity is too high the injera does not flow to the edge of the mitad, is thicker than desired, cooks more slowly, has larger eyes, and is harder to handle.
Having spent a couple of weeks verifying the described features and issues, it was time to try some variations on the general theme and see if there was any significant difference in the result.
First, I tried raising the fermentation temperature to the reported optimum of 37°C/99°F and was amazed by the increase in fermentation rate and reduction in the time required to deplete the fermentable sugars and halt the generation of CO2. At 99°F the primary fermentation was complete in less than six hours (since it is a very liquid batter with no gluten to give it structure, it may rise and collapse multiple times before the yeast run out of food). Mixing the batter using 120°F water produced a 100°F batter so that there was no delay in getting it up to the 99°F fermentation chamber temperature and reduced the time needed to rise and fall once and develop a nice sour flavor to about 4:30 from mixing the ingredients and the secondary fermentation completed in about 90-120 minutes followed by 90 minutes in the refrigerator to slow it down, cool it off, and allow it to absorb the CO2 suspended in the batter as bubbles. This CO2 promptly comes out of solution to form the "eyes" when the batter is poured on the griddle.
If the objective is to cook the injera when the CO2 trapped in the batter is maximized, the strategy that seems to achieve that end seems to be to allow it to ferment until it reaches 80-90% of maximum height without collapsing then refrigerate the batter to dissolve as much of the trapped CO2 in the liquid phase as possible.
There is some point at which if you don't refrigerate it, the continuing production of CO2 will outstrip the capacity of the batter to hold it and the batter will collapse anyway. If you begin cooling it too soon, the batter cools down and stops producing CO2 before it has depleted the fermentable sugars. So it is a fine line that encourages a slightly early termination of secondary fermentation to avoid a collapse before the batter has absorbed the maximum amount of CO2.
It is also possible that if there are fermentable sugars remaining in the batter when the temperature has stabilized at the final storage temperature, fermentation may continue (slowly) for an extended period of time keeping the batter loaded with CO2 and capable of being converted into freshly baked injera with lots of eyes. Since the source of fermentable sugars to support the secondary fermentation is the abjit, it may be (speculation here on my part) that increasing the amount of absit that is added back to the batter may influence how long the batter can be stored and still be used to make high quality injera, though unless the absit is made with excess water, increasing the absit may make the batter too viscous to pour properly.
Thus I offer my current modified improved method for making enough batter for 1.8 - 14" diameter injera cooked on a 16" griddle:
{why 1.8 injera you ask? - because that much fits into a one quart wide mouth Mason jar without overflowing}
Ingredients:
40g starter + 250g water (@110°F )+ 180g teff (@105°F) + 5g salt (added to the water)
then for absit/tangzhong
25g teff + 180 water make absit (~1:7)
Process:
- Place the starter in a bowl and add the warm water, whisk to combine
- Add teff flour and slowly whisk it in until the batter is smooth (a whisk with fewer rather than more wires helps keep the flour from splattering)
- Pour into a container with sufficient head space to allow a 70% volume expansion (it will expand by at least 50% and you don't want it to overflow).
- Place the batter in a 99°F fermentation chamber or well controlled low temperature oven (combi. or an oven with a light on that you have confidence will settle at ~99°F) and let it ferment for 6:00; remove and stir down the foam then put it back to ferment for another hour. At 5:00 stir down again and let it sit at 99°F for another 20 min or so; it should not rise again. This seems to be the indication that all of the fermentable sugars have been consumed. Taste to be sure that it is appropriately sour (if not let it sit longer since yeast and LAB have different cycles).
- Mix and cook the tangzhong by combining the 25g of teff flour with the 180g of water, mixing until they make a smooth slurry. Cook over medium heat until the tangzhong reaches 180°F, stirring constantly; when it reaches the fully gelatinized state the scraper will leave a permanent streak on the bottom of the pan. Remove pan from the heat and continue stirring over a bowl of cool water until the tangzhong reaches ~130°F before adding to the injera batter and whisking it in.
- Adjust the viscosity at this point if needed. I have found that it seems still a little thick at this point but will thin out during secondary fermentation. Put the container back into the 99°F fermenter and allow it to undergo a second fermentation for about 90 min to 2 hrs;
- Then transfer it to a refrigerator without mixing and leave it to cool off for 90 minutes or so. The level of the mixture will recede to near the level at the beginning of the secondary fermentation when it is fully cool and the CO2 has been fully dissolved in the batter. Stir well to re-suspend the solids (resist the tempatation to make viscosity adjustments here) and pour onto the griddle.
- Heat the griddle to 330°F (based on IR thermometer measurement) and spray the griddle with a very small amount of non-stick spray (vegetable oil + lecithin) before pouring batter in the middle and picking up the griddle and rotating it to spread the batter to the edge. I found that 325ml at the appropriate viscosity (to test the viscosity, it should pour smoothly from a 3 oz ladle in a few seconds at a height of about 8" without breaking up into droplets) will spread all the way to the edge of a 16" griddle.
- Turn up the thermostat to 400°F and cook uncovered until about 70% of the surface looks dry and then put the lid on for a minute (steam will be coming out of the lid by then) before removing. Wait for the bottom surface to become sufficiently cooked that there is an obvious separation at the outer radius where you can get a thin Teflon or other high temperature spatula (or lefse stick) under the injera then use a sefed to transfer it from the griddle to a cloth surface where it can cool off and lose some of the moisture. If you use a lower temperature you can turn the griddle up to 400°F after taking the lid off to hasten the final cooking stage so that it comes off the griddle sooner and more easily. But you have to wait for it to be ready - otherwise it will stick badly to the spatula.
- Do not try to stack until they are fully cool and no longer sticky on the surface.
- If you find that there is not enough dissolved CO2 in the batter to make the eyes you like, add about 2t of baking powder (not baking soda) per quart of batter and stir it in. Wait a minute or two before continuing to fry injera. I have found that at this concentration the baking powder leaves no distinctive taste.
Jan 28, 2022 - a note of some potential significance:
I was pointed to a video on YouTube [2] where a chef makes beautiful injera without any absit, which poses the question "what makes absit important"? Thus far I have been operating under the assumption that the absit is needed to pump up the dissolved CO2 in the batter just before cooking the injera to form the eyes. But it seems clear that the incorporation of absit followed by a secondary fermentation is perhaps not an essential step if you can get the CO2 into the batter via another route. This opens up a range of options going forward. I am already fermenting injera batter in eight hours which bypasses mold and aerobic yeast growth on the surface of the batter as well as reducing the planning time. Making the absit and timing the addition relative to when you want to cook them remains a process constraint that now may conceivably have a workaround. In the video you will notice that the chef has three griddles, of which two are from ADDIS. This is the model that I finally selected after some considerable study, but I will not make this into an ad more than to say that my rationale for selecting it turned out to be valid.
July 30 2022 - see an added comment below with a 30 July 22 date [3] for how to refresh and maintain an injera starter.