Sapna's Idli

One of my comfort foods!!
Even though my family is from the Northeast, South Indian food is a staple at home. I’m not sure if you’re from South India. Since fermentation takes time and effort, and split black lentils (urad dal) are less available in Japan, I make rava idli (idli made with semolina) using plain curd and Eno (a fruit salt that acts as a leavening agent) instead of baking powder for a quick version. Do you eat idli regularly at home, too, or is it more of a special treat?

Thank you so much for sharing this easy recipe. I will definitely try it because I love eating idli, it offers so many health benefits along with a delicious taste. Although I am not from South India, eating idli regularly at home is quite common for me because of its light texture, great flavor, and nutritional benefits.

Thank you for the introduction.
Since I also study microorganisms—specifically rhizobia—as part of my research, I’d like to ask a question from a microbiological perspective.
Besides Leuconostoc mesenteroides and Streptococcus thermophilus, are there any microorganisms in idli batter that have particularly interesting or unique capabilities?

Thank you for the introduction and for your thoughtful question.
From a microbiological perspective, idli batter is indeed a fascinating natural fermentation system with a diverse microbial community beyond Leuconostoc mesenteroides and Streptococcus thermophilus.

One particularly interesting group is lactic acid bacteria such as Lactobacillus spp. (e.g., Lactobacillus fermentum and Lactobacillus plantarum). These microorganisms contribute to acidification, improve batter texture, and enhance flavor development. Some strains also have probiotic potential and can increase the bioavailability of minerals by reducing antinutritional factors like phytates.

Another important microorganism is yeast, especially Saccharomyces cerevisiae. Yeasts play a key role in carbon dioxide production, which helps in leavening the batter and gives idli its characteristic soft and porous structure. Additionally, yeast–bacteria interactions create a balanced fermentation environment, supporting stable microbial growth.

Some studies have also reported the presence of Enterococcus spp., which can contribute to flavor complexity and enzymatic activities, though their role is still being explored and is strain dependent.

Overall, idli batter fermentation is a great example of a synergistic microbial ecosystem, where bacteria and yeasts work together to improve texture, nutritional quality, and sensory properties. This makes it a particularly interesting system from a microbiological and food fermentation research perspective.

Thank you for your interesting story.
I don't know much about how bread is made, and I thought it was generally fermented with yeast alone, but I learned for the first time that you can make delicious bread using lactic acid bacteria as well.
Is there a difference in texture between bread fermented with yeast alone and bread fermented with lactic acid bacteria? The photos of the idlis are white and cute, and they all look delicious, so I definitely want to try some.

Thank you for your presentation about idli. This was my first time learning about it, and it made me curious about its taste.
I have a few simple questions:

1. What is urad dal? Is it a type of legume or a cereal grain?
2. How long is idli batter typically fermented to achieve good quality?
3. Are any seasonings added to idli batter? If not, how would you describe the taste of idli?

Thank you for your presentation. Good to know! I want to try idlis someday.
Especially, idli moulds are interesting for me. Do most people in South India have moulds? Also, when steaming the batter, do you stack the moulds as shown in the photo on slide 5 to make several idlis at once?

This is a slightly sour steamed bun that is often served for breakfast in India, isn't it? To be honest, I have not been very fond of its distinctive flavor. However, thanks to your slides, I learned that the sourness comes from fermentation by Leuconostoc mesenteroides and Streptococcus thermophilus. Understanding this background has helped ease my hesitation toward unfamiliar flavors. Thank you very much for the informative explanation.

May I ask how long the fermentation should be in step 3 of the recipe? Specifically, how long should it be left at room temperature?

That's a very unique food indeed. In Japan, we have things like manju that are slightly fermented and then finished by steaming, so they seem somewhat similar, yet they also look a bit different. How often is this dish eaten in India?

Thank you Wakazono San for your question.

Yes, there is a noticeable difference in texture between bread fermented with yeast alone and foods fermented with lactic acid bacteria. Bread made only with yeast rises mainly because yeast produces carbon dioxide, which creates larger air pockets in the dough. As a result, the texture is usually light, airy, and slightly chewy, with an elastic crumb structure and a mild, bready flavor. Since yeast fermentation produces very little acid, the taste remains relatively neutral and soft.

In contrast, fermentation involving lactic acid bacteria, such as in Idli or sourdough, leads to the production of organic acids along with gases. These acids gently modify the starch and protein structure, giving the final product a softer, moister, and tender texture with finer and more uniform pores. The mild acidity also improves digestibility and adds a subtle tangy flavor, which makes the food feel lighter on the stomach. In the case of idli, the combined action of lactic acid bacteria and natural yeasts, followed by steaming rather than baking, produces the characteristic white, fluffy, and spongy structure. This is why idlis look soft and cute in appearance and feel so light and pleasant when eaten, making them both delicious and easy to digest.

Thank you Nahdiah San for your question.

Urad dal is a type of legume, not a cereal grain. It comes from black gram (Vigna mungo) and is widely used in Indian cooking. In idli batter, urad dal plays a very important role because its proteins and soluble polysaccharides help trap air during fermentation, which gives idli its soft and fluffy texture.

Idli batter is typically fermented for 8 to 12 hours, depending on temperature and climate. In warmer conditions, fermentation can be complete in about 6–8 hours, while in cooler environments it may take up to 12–16 hours. Proper fermentation is indicated by an increase in batter volume, a light airy texture, and a mild, pleasant sour aroma.

Usually, no seasonings are added to the idli batter itself. The batter is made simply from rice, urad dal, water, and salt. Because of this, idli has a very mild, slightly tangy, and neutral taste. Its flavor is subtle rather than strong, which is why it is commonly eaten with flavorful side dishes such as sambar and chutney. This mild taste also makes idli easy to digest and suitable for people of all ages.

Thank you, Satsuki San, for your question.
Yes, you should definitely try idlis, I’m sure you will like them and enjoy their soft texture and mild, comforting taste.

Yes, idli moulds are very common in South India. In many households, especially in regions where idli is eaten regularly for breakfast, having an idli mould and a steamer or pressure cooker is almost as basic as having a rice cooker. Even today, most families keep traditional metal idli moulds at home, although silicone and non-stick versions are also becoming popular.

When steaming the batter, the moulds are usually stacked vertically, just like in the photo you saw on slide 5. Each plate holds several round cavities, and multiple plates are placed one above another on a central rod. This stacked arrangement allows many idlis to be steamed at the same time in a single pot or steamer. The steam circulates evenly around the stacked moulds, ensuring that all the idlis cook uniformly. This method is efficient and practical, especially for families, and it’s one of the reasons idlis can be prepared quickly for everyday meals.

Thank you very much Mayumi San for sharing your honest impression, and I’m really glad to hear that understanding the science behind fermentation helped reduce your hesitation toward the flavor.

In step 3 of the recipe, the idli batter is typically left to ferment at room temperature for about 8–12 hours. Under warm conditions (around 25–30 °C), fermentation is usually complete within this time. In cooler environments, it may take a bit longer, sometimes up to 14–16 hours. A well-fermented batter will show a noticeable increase in volume, a light and airy consistency, and a mild, pleasant sour aroma rather than a sharp acidity. Fermenting beyond this point can make the idlis too sour, so gentle, moderate fermentation is ideal for achieving good flavor and texture.

Thank you Natsuki San, that’s a very nice comparison, and you’re right, idli and steamed foods like manju share some similarities, especially in being fermented and then steamed, even though their ingredients and flavors are quite different.

In India, idli is eaten very frequently, especially in South India. For many people, it is a regular breakfast food, often eaten several times a week and sometimes even daily. Because idli is light, easy to digest, and not oily, it is also commonly served to children, elderly people, and those recovering from illness. Beyond breakfast, idli can also be eaten as a light dinner or as part of a meal when something gentle on the stomach is preferred.

Outside South India, idli is still widely available and popular, though it may be eaten less frequently at home and more often in restaurants. Overall, idli is not only occasional or festive food but also an everyday, comfort food for many Indians, valued for both its simplicity and its nutritional benefits.