What Foods Contain Leghemoglobin?

December 25, 2025 •

4 min read

A protein known as leghemoglobin is found in the root nodules of legumes, where it is vital for nitrogen fixation, but you won't find it in most traditional foods. This article explores what foods contain leghemoglobin, from its natural source to its innovative and widely discussed use in specific plant-based meat products.

Quick Summary

Leghemoglobin is naturally present in the root nodules of legume plants but not in the edible parts. Commercially, it's produced through a process of yeast fermentation and used as an ingredient in specific plant-based meats to replicate the flavor and aroma of cooked meat.

Key Points

Leghemoglobin's Natural Source: Found in the root nodules of legumes like soybeans, but not in the edible parts of the plant.
Commercial Production Method: It is produced for food applications using precision fermentation of genetically engineered yeast, not by extracting from plant roots.
Primary User: Impossible Foods is the key company using soy leghemoglobin to replicate the meaty flavor and appearance in their plant-based products.
Function of Heme: The heme molecule within leghemoglobin is what provides the characteristic red color and savory, meaty taste when cooked.
Safety and Regulation: Food-grade leghemoglobin has been thoroughly tested for safety and approved by major food safety authorities, including the FDA and Health Canada.
Distinction from Myoglobin: While functionally similar for creating meaty flavor, leghemoglobin is a plant protein, distinct from the myoglobin found in animal muscle.

What is Leghemoglobin?

Leghemoglobin is a heme-containing protein, similar in structure to the myoglobin found in animal muscle, but it exists in the plant kingdom. Heme is the iron-containing molecule that gives both blood and cooked meat their reddish-brown color and distinct flavor. In plants, leghemoglobin serves a crucial biological purpose, while in the modern food industry, it serves an innovative culinary one.

The Natural Source: Legume Root Nodules

Naturally, leghemoglobin is found in the root nodules of leguminous plants, such as soybeans, peas, and peanuts. These nodules are special structures that form on the plant roots in a symbiotic relationship with nitrogen-fixing bacteria. The leghemoglobin’s primary function is to buffer the oxygen concentration within the nodules. This creates a low-oxygen environment, which is necessary to protect the oxygen-sensitive enzyme, nitrogenase, that the bacteria use to convert atmospheric nitrogen into ammonia for the plant. Since these root nodules are not a typical part of the human diet, leghemoglobin is not found in the conventionally edible parts of these plants.

The Commercial Application: Plant-Based Meat

For most people, the name leghemoglobin is linked to the company Impossible Foods. Impossible Foods scientists discovered that the heme molecule within leghemoglobin plays a significant role in creating the flavors and aromas of cooked meat. This discovery led them to develop a way to produce soy leghemoglobin at a large scale for use in their products, such as the Impossible Burger. By adding this ingredient, their plant-based burgers, sausages, and pork can mimic the sensory experience of cooking and eating meat, including the red color and sizzling qualities.

The Production of Food-Grade Leghemoglobin

Since harvesting leghemoglobin directly from soybean root nodules is neither efficient nor sustainable, Impossible Foods uses a process called precision fermentation. This method involves the following key steps:

Genetic Engineering: Scientists insert the soy leghemoglobin gene into a genetically engineered yeast, Pichia pastoris.
Fermentation: The yeast is grown in a controlled, industrial fermentation process, where it multiplies and produces large quantities of the leghemoglobin protein.
Extraction and Purification: After fermentation, the yeast cells are harvested and lysed to release the soy leghemoglobin. The protein is then isolated, filtered, and concentrated.
Ingredient Formulation: The resulting concentrated liquid, containing soy leghemoglobin, yeast proteins, and stabilizers, is then added to Impossible Foods' products.

This method allows for sustainable and scalable production of the ingredient without the need to destroy soybean plants.

Natural vs. Fermentation-Produced Leghemoglobin

The leghemoglobin produced via fermentation is identical to the one found naturally in soy root nodules, but their contexts are very different. The table below highlights some of the key differences and similarities.


Feature	Natural Leghemoglobin (Root Nodules)	Fermentation-Produced Leghemoglobin (Ingredient)
Source	Root nodules of legumes (e.g., soybeans)	Genetically engineered yeast (Pichia pastoris)
Availability	Inaccessible; part of the plant root system	Mass-produced for commercial food production
Food Context	Not in common, edible foods	Ingredient in specific plant-based meat products
Purpose (in product)	Vital for nitrogen fixation	Provides meat-like flavor, color, and aroma
Heme Molecule	Contains heme, identical to fermentation version	Contains heme, identical to natural version

The Role of Heme in Leghemoglobin

The functional part of leghemoglobin is the heme, an iron-containing molecule. Heme is ubiquitous in nature, present in every living cell, from plants to animals. In animal muscle, it is found in myoglobin, which is a major contributor to meat's characteristic flavor and color. The genius of using soy leghemoglobin is that its heme is functionally identical to the heme in animal myoglobin, allowing it to recreate the familiar meaty flavor when heated during cooking. This is a major reason why Impossible Foods' products are praised for their meaty flavor compared to earlier generations of meat alternatives.

Is Leghemoglobin in Food Safe to Eat?

For those concerned about consuming a novel food ingredient, soy leghemoglobin has undergone extensive regulatory scrutiny. Food safety authorities around the world have rigorously evaluated the ingredient, and several have issued approval for its use.

For example:

U.S. Food and Drug Administration (FDA): Issued a "no questions" letter for its Generally Recognized As Safe (GRAS) notification.
Health Canada: Notified Impossible Foods that it has no objection to the use of soy leghemoglobin in simulated meat products.
European Food Safety Authority (EFSA): Declared soy leghemoglobin safe for consumption in specific meat analogue products.

The extensive testing included evaluations for potential toxicity and allergenicity, with no safety issues identified at the approved usage levels. Additionally, cooking and digestion are expected to denature the protein, breaking it down into harmless components.

Conclusion

Leghemoglobin is a fascinating heme-containing protein with a dual identity: a vital component for natural nitrogen fixation in legume root nodules and a groundbreaking ingredient in modern plant-based meat substitutes. The protein is naturally present in soybeans but is commercially produced through yeast fermentation for food use, a sustainable and efficient process developed by Impossible Foods. This innovative use of leghemoglobin is what gives Impossible products their signature meaty flavor and appearance, fundamentally altering the landscape of meat alternatives. Thanks to extensive safety testing and regulatory approval, food-grade soy leghemoglobin is considered safe for consumption. For consumers, this means enjoying the familiar taste and experience of meat without relying on animal agriculture.

For more information on the ingredient, you can refer to the manufacturer's resource Impossible Foods on Heme.

Frequently Asked Questions

No, leghemoglobin is a protein derived from plants, specifically legumes. The version used in food products, such as those from Impossible Foods, is produced using a plant gene (from soy) but is made in yeast via fermentation.

No, leghemoglobin is only found in the root nodules of the soybean plant, not in the beans themselves. Therefore, it is not present in products like tofu, soy milk, or edamame.

It is produced using a fermentation process. Scientists insert the soy leghemoglobin gene into a specific type of yeast, which is then grown to produce large quantities of the protein.

Yes, food-grade soy leghemoglobin has been deemed safe by major regulatory bodies like the U.S. FDA, Health Canada, and EFSA after extensive safety testing for toxicity and allergenicity.

It is used because the heme molecule in leghemoglobin creates the distinct flavors and aromas that are characteristic of cooked meat. This allows plant-based products to more closely mimic the sensory experience of eating meat.

No, leghemoglobin is a specific ingredient used primarily by Impossible Foods. Many other plant-based meat companies use different ingredients and methods to achieve their desired taste and texture.

The presence of leghemoglobin is a key factor in the taste of Impossible products. When heated during cooking, the heme catalyzes reactions that produce the unique savory flavors associated with meat.