What is the sticky stuff in natto: Unraveling the Gooey Mystery

For many Americans encountering natto for the first time, the most striking – and often off-putting – characteristic is its distinctive sticky, slimy texture. This gooey substance is not merely an aesthetic quirk; it's the very essence of what makes natto unique and, for those who appreciate it, incredibly beneficial. So, what exactly *is* this sticky stuff?

The Science Behind the Stickiness: Polysaccharides and Amino Acids

The sticky nature of natto is primarily due to a complex network of substances produced during its fermentation process. The main culprits are:

Polyglutamic Acid (PGA): This is a protein-like polymer made up of many individual glutamic acid molecules. PGA is a highly viscous and hygroscopic substance, meaning it attracts and holds onto water. During the fermentation of soybeans to create natto, the bacteria responsible, Bacillus subtilis, produce significant amounts of PGA. This is what forms the characteristic sticky strands or "strings" when you stir natto. Think of it like a natural, edible gelatin.
Fructans: These are types of complex carbohydrates (polysaccharides) that also contribute to the slime. They are essentially chains of fructose sugar molecules. Like PGA, fructans have a viscous quality and play a role in the overall texture.
Other Amino Acids and Peptides: The fermentation process breaks down the proteins in soybeans into smaller peptides and individual amino acids. Some of these also contribute to the overall viscosity and mouthfeel, though PGA is the dominant player in creating those long, stretchy strings.

The Role of Fermentation

It's crucial to understand that this sticky substance is a direct result of fermentation. Natto is made by fermenting cooked soybeans with a specific bacterium, Bacillus subtilis var. natto. This bacterium thrives on the nutrients in the soybeans and, as a byproduct of its metabolic activity, excretes these sticky compounds. Without this controlled bacterial action, soybeans remain just soybeans – firm, relatively dry, and decidedly not sticky.

Why is it Important? The Nutritional and Functional Significance

This sticky goo isn't just for show; it's where a lot of natto's celebrated health benefits come from.

Key Beneficial Compounds Found in the Stickiness:

Nattokinase: This is perhaps the most famous compound associated with natto. Nattokinase is an enzyme that is produced by Bacillus subtilis during fermentation. It's known for its potential to help break down blood clots, promote healthy blood circulation, and support cardiovascular health. While nattokinase itself isn't directly the sticky substance, it's produced *alongside* and *within* the matrix of sticky compounds.
Vitamin K2: Natto is one of the richest dietary sources of Vitamin K2 (specifically MK-7). Vitamin K2 is essential for bone health (helping calcium deposit into bones) and cardiovascular health (helping prevent calcium from depositing in arteries). The sticky goo helps to encapsulate and stabilize Vitamin K2, making it readily available for absorption.
Probiotics: Bacillus subtilis is a beneficial probiotic bacterium. Consuming natto introduces these live and active cultures into your gut, which can contribute to a healthier gut microbiome and improved digestion. The sticky slime acts as a protective medium for these probiotics.
Dietary Fiber: The complex carbohydrates contributing to the stickiness also provide dietary fiber, which is important for digestive health.

The sticky nature of natto also contributes to its unique flavor profile and how it interacts with other ingredients when used in cooking.

The sticky, stringy texture of natto is a direct result of the fermentation process, primarily driven by the production of polyglutamic acid (PGA) by the bacterium Bacillus subtilis. This slime is not just a textural element; it's a carrier for many of natto's most potent health benefits, including nattokinase and Vitamin K2.

How to Approach the Stickiness

For newcomers, the stickiness can be a hurdle. Here are a few tips:

Stirring is Key: The more you stir natto, the more pronounced the stickiness and stringiness become. Some people find that stirring vigorously for a minute or two incorporates the strands and makes the texture more uniform and palatable.
Mix with Other Flavors: Natto has a strong, pungent, fermented flavor that can also be an acquired taste. Mixing it with soy sauce, mustard (Japanese karashi is traditional), chopped scallions, or even a touch of mayonnaise can help to balance the flavor and make the texture more approachable.
Start Small: Don't feel obligated to eat a large portion at first. Start with a small amount and gradually increase it as you become accustomed to the taste and texture.

In Summary

The sticky stuff in natto is a testament to the power of fermentation. It's a complex matrix of beneficial compounds, primarily polyglutamic acid, that not only gives natto its signature texture but also acts as a vehicle for its impressive nutritional profile. While it might be unusual to American palates, understanding its origins and purpose can help demystify this unique food and open the door to its many health advantages.

Frequently Asked Questions About Natto's Stickiness

How is the sticky stuff in natto formed?

The sticky substance is formed during the fermentation of soybeans by the bacterium Bacillus subtilis var. natto. This bacterium breaks down soybean proteins and carbohydrates and, as a metabolic byproduct, excretes compounds like polyglutamic acid (PGA) and fructans, which create the viscous, stringy texture.

Why is the sticky stuff important for natto's health benefits?

The sticky matrix acts as a natural carrier and protective layer for some of natto's key nutrients and beneficial compounds, such as the enzyme nattokinase and Vitamin K2. This encapsulation helps to stabilize these substances and makes them more bioavailable for the body to absorb and utilize.

Does all fermented soybean food have this sticky stuff?

No, this specific sticky texture is characteristic of natto. While other fermented soybean products like tempeh or miso also undergo fermentation, they utilize different microorganisms and processes, resulting in distinct textures and flavors without the prominent stringiness of natto.