Lentil protein concentrate - towards lentofu
What is Lentofu?
So I've been concentrating on the topic of home-accessible lentil-based meat alternatives - lentofu. I found it really hard to get soybeans here, so focused on lentils. My issue with many plant-based meat alternatives is that their protein content is rather low. E.g. mushrooms have basically no nutritional value, and bean burgers and tofu are pretty high in carbs. Not to mention lentils themselves which can have an offputting texture. Someone looking for the vegetarian equivalent of plain eggs doesn't have many options that don't involved highly processed funky tasting powders.
The issue with simply making tofu out of lentils is that while most of the proteins in soy are soluble in tap water, most of the proteins in lentils are not. The typical soy production process doesn't work on lentils. But I know that cooking the protein should be able to set a gel (based on earlier research when I was trying to make pectin gels to process waste fruit peels), and looked up a lot of literature on extracting lentil proteins. I found that these proteins can make a strong foam and gel, which is what I'm targeting for a lentil-based protein food product.
Why lentils?
1) They're cheap,
2) Canada is the world's largest producer so the supply is reasonably secure (This is the implicit Confederation deal: the east provides the market, skilled labour, supplies and infrastructure; the west grows the dryland crops. If this deal collapses I've probably already died),
3) they are so high in protein that the residue is equivalent in macronutrient profile to plain wheat flour, which fits great into the rest of my diet for minimal waste, and
4) bonus ERE points for anything lentil related.
Producing the lentil protein concentrate
I spent the last week extracting protein from lentils. I followed the method from Jarpa (2015) in particular for this experiment.
Start with 500g of hulled split red lentils.
I blended them in a food processor with 1 L tap water. I didn't blend them as finely as I would've liked, should have split it into two batches and sieved it. I then added an additional 4 L tap water and 0.7g sodium carbonate (the proper amount would be around 0.4-0.5g but I'm not sure how strong mine was as it was old). Legumin dissolves in basic solutions but not neutral or acidic. An alternate route is to make a strong brine, but without a centrifuge I didn't want to try it and risk ruining the edibility.
I stirred it at 22 C for an hour to dissolve the legumin proteins. I should've used hot tap water at 30 C instead for higher extraction. Getting the water too hot might denature the proteins and prevent concentration, so I recommend not heating it on a stove. After stirring, I let the mixture settle, and drained off the loaded solution. I added 50 grams of 5% white vinegar to the loaded solution. Immediately a very fine (felt like ~400 mesh/37 micron) beige precipitate fell out of solution, leaving behind a yellowish whey. The vinegar makes it smell a bit unpleasant so I would recommend using citric acid next time.
I allowed this to settle for 24 hours. It was so fine that the precipitate either clogged or passed through everything I could use to filter it. I instead just removed the whey as it settled. This produced a roughly 5.4% solids concentrate. I dried it for 12 hours at 40 C and it reduced to about 27% solids. I froze the rest. It turned salmon/red as it dried.
Using the whey and pulp
I had saved all the whey because the water-soluble fraction of the proteins (albumin) should be dissolved in it. I boiled it to denature and crash out the albumin, which duly coagulated into white ~2 mm flakes. I put this all through a coffee filter to concentrate the albumin. After cooking and filtering the remaining liquid was very clear and colourless. I discarded the liquid and ate the albumin, it tasted like flaky egg whites. I'm looking for a way to concentrate the albumin without cooking or vacuum evaporation, as it would be really useful to improve the lentofu heat resistance.
I noted that the remaining pulp is nutritionally equivalent to wheat flour. I added lemon juice to neutralize it, some salt and baking soda. I made pancakes with this pulp and ate it through the week with some peanut butter and jam. With the reduced protein and pureeing it had a texture kind of like bread pudding. It was much easier to eat than soy pulp/okara which tends to be pretty dry and messy. So nothing went to waste!
Results
I finished with a total of about 75g of concentrate and 25g of albumin from 500g lentils. This is equivalent to about 270g of chicken breast so is about 1/3rd the cost per gram of protein. Assuming the concentrate is 84% crude protein, I achieved 43% recovery of protein to the concentrate, and 10% recovery to the whey albumin. This is a 53% overall protein recovery. In the paper they achieved 54% to concentrate and ~67% overall, but they had grinding mills and centrifuges.
Vegan lentil muffins
I created a 5% solids concentrate to test the protein as an egg replacement, again following Jarpa's recipe:
200g flour
260g sugar
3g baking powder
47g cocoa
330g 5% lentil protein concentrate
160g oil
Bake at 175C for 30 minutes
This made about 14 muffins:
Internal texture:
The muffins tasted great and were pretty much indistinguishable from a regular muffin, though I think I would reduce cooking time by 2-3 minutes. I'm going to try other applications of this concentrate as an egg replacement in the future. I was excited to get on with the lentofu part of this experiment.
Lentofu - attempt 1
I read from other papers investigating lentil gels that 12% concentrate would produce a pretty strong gel. I read from Jarpa that adding guar gum in some unknown amount would make it even stronger. So I made a 12% lentil protein concentrate, 5% guar gum solution. I put it in a covered metal bowl and cooked it in a water bath at 90C for 20 minutes. After this it was very runny, but as it cooled it became a very thick gel, with texture similar to cheddar cheese. I marinated it in garlic, sugar and soy sauce for a day in the fridge. It actually absorbed some of the sauce and discoloured!
I cut it up and fried it. Unfortunately it melted a bit on the bottom until the bottom skin dehydrated enough to hold everything together. I would recommend frying in a very hot pan or deep frying. I am going to add cornstarch in the next iteration to see if that improves high-temperature resistance.
I ate it! The texture is kind of grainy, and because it softens at high temperatures, when served warm it's comparable to a grainy cream sauce. A bit cooler and it's like soft mechanically separated chicken. It's a really unique kind of food. It was fairly moreish and got an "it's not meat, but it's okay, I'll eat more if you make it" rating which is a pretty good Wife Acceptance Factor.
I know ERE has moved beyond saving the world with lentils to saving the world with pastel rainbows, but I think there's still a lot of mileage yet for the lentil part!