May 2021 - Chickpea tempeh, My friend Rhizopus, and Antinutrients

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My dear readers,

I hope you are doing well!

Two weeks ago, I was invited to teach how to make chickpea tempeh in a fermentation course in Taipei. I took this opportunity to review food blogs and scientific papers about chickpea tempeh, and I wrote a review post on the blog.

Here is a summary of what I found!

Chickpea tempeh: a review of online recipes

Do you know tempeh?

It is a traditional fermented food from Indonesia. It is made by fermenting soybeans with a mold called Rhizopus oligosporus. When you put spores of Rhizopus — its seeds — in contact with soybeans, the spores germinate, and tiny filaments start to grow. These filaments are the body of the mold, they are called mycelium.

When I grew Rhizopus a couple of years ago, my father was so amazed by this cute mycelium that he couldn’t help but take this beautiful picture of it.

Mycelium growing on tempeh.

The mycelium grows around the soybean seeds, which binds them all together and creates this cohesive cake that we call tempeh. Here I made a time-lapse showing the growth of the mycelium over 32 hours.

There is a variation of tempeh that you can make with soy pulp, also called soy okara. I also wrote a recipe to make okara tempeh. Below, I grew okara tempeh in a banana leaf.

Okara tempeh growing in banana leaf.

But people are trying more creative variations of tempeh, using any legume or grain, like black bean, chickpea, wheat, rice, etc. Rhizopus loves legumes and grains, and, from each substrate, it develops specific flavors.

Chickpea tempeh is an interesting variation for people who eat soy-free, people who don’t like the beany taste of soybean, or in countries where chickpea is more common than soy.

Chickpea tempeh ready to be cooked.

I searched the most informative online chickpea tempeh recipes in English and French. And I summarized the best fermentation conditions and the different variations in the recipe.

For instance, some people use tinned chickpeas to save time. One lady germinates her chickpea before the fermentation to increase digestibility. Most people use perforated plastic bags to grow Rhizopus, but some people try to reuse plastic boxes or use glass containers. Then we need to put the containers in a warm place to mimic the tropical conditions of Indonesia. Some people will use slow cookers or dehydrators. Others show how to make a simple DIY incubator with cardboard or propose to use elegant wooden boxes.

If you want to try to make chickpea tempeh, I invite you to start with the review I wrote! From there, you can pick the recipe that you prefer.

Of course, we also did some additional experiments with Rhizopus to investigate some aspects of the recipes that were lacking or a bit vague.

Ah, I spend really good times with Rhizopus. When he is growing for 2 days on the shelf, I feel that I am taking care of a silent pet. He is such a good friend. And we are such a good research team. I have so many ideas of experiments to do with him, he always kindly agrees to give it a try. And, each time, despite his apparent silence, he teaches me profound lessons on life.

I cannot wait to share our next experiments with you later!

But before, there is another point that I investigated in this chickpea tempeh review: antinutrients.

Using fermentation to improve nutrition

Nowadays, fermented foods are trendy because of their many benefits. Fermentation is making fun microbiology at home, it increases the shelf life of food, helps develop complex and tasty flavors like umami, starts digesting proteins, adds up digestive enzymes that support our digestion, creates additional nutrients like vitamins, and increases the number of microorganisms, that is, “probiotics”.

Another benefit of fermentation is that it improves food digestibility by breaking down some antinutrients. Antinutrients are molecules that we naturally find in food. We call them antinutrients because they limit our ability to digest and assimilate nutrients.

Grains and legumes are usually rich in antinutrients, precisely because plants don’t really want us to digest their seeds. That is why we may not digest them very well. For instance, I know a few people in Taiwan who burp after drinking soy milk. Or, after eating beans, we may have gas or feel discomfort in the belly. These are signs of impeded digestion.

Chickpeas contain two common antinutrients: phytic acid and trypsin inhibitor. Phytic acid limits the absorption of minerals in our small intestine. And trypsin inhibitor limits the digestion of proteins in our small intestine by binding to trypsin which is arguably our most important protein enzyme synthesized by the pancreas.

So, I wondered how my friend Rhizopus could help me deal with these two antinutrients in chickpea?

To answer this question, I reviewed all the scientific papers that I found about chickpea tempeh. And I also integrated this in the same review post.

Yes, there are scientists who write serious research papers on chickpea tempeh! Like us, they do their best to grow their tempeh, and then, depending on their research question, either they ask people to taste and score their culinary creations, or they coldly crush their beautiful tempeh into powder to measure its content in every single nutrient and antinutrient.

And here is what I found: during the transformation of chickpea into chickpea tempeh, antinutrients decrease by about 80%. This is quite impressive in just 2 days of fermentation, and, as the scientists say, it makes chickpea tempeh a good option for digesting and assimilating properly plant proteins.

But, in the process, soaking and cooking also play a significant role, as you can see on this diagram:

Lowering of the amount of antinutrients during chickpea tempe making.

When we soak the chickpeas, some antinutrients dissolve in the water. When we boil the chickpeas, more antinutrients dissolve in the water and break down due to heat. Finally, when we ferment the cooked chickpeas, our friend Rhizopus breaks down even more antinutrients thanks to its digestive enzymes.

If you are interested in what happens when we transform chickpea into chickpea tempeh, I also summarized in the same post the effect on macronutrients, essential amino acids, protein digestibility, and minerals content.

And what about other substrates or other fermentation kinds? For instance, miso uses another mold, called Aspergillus. Or yogurt and fermented vegetables usually work with lactic acid bacterias. Later, I would like to reproduce this visual representation of antinutrient decrease for other kinds of fermentations.

I think that this can help us understand a bit better how we can, at the same time, have fun with our micro-friends, learn profound lessons on life, and improve the digestibility of seeds, grains, and legumes.

That’s it! I hope you enjoyed it!

Until next time,

Cheers,

Lénaïc

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