Few people realise how much science sits behind some modern plant-based meat products. In some cases, manufacturers have even developed ways to recreate the red, “bleeding” appearance traditionally associated with meat.
For many people, the experience can be surprising. Cut into some plant-based burgers and a red liquid appears, closely resembling the juices associated with rare meat. Given that no animal products are involved, an obvious question follows: what exactly creates that effect?
The answer lies in a little-known protein called soy leghemoglobin.
What Creates The Red Colour?
The red liquid found in some plant-based meat products comes from soy leghemoglobin, a naturally occurring protein found in the root nodules of soybean plants.
The name itself gives us a clue. Leghemoglobin is short for “legume haemoglobin” – “leg” referring to legumes such as soybeans, and “haemoglobin” referring to a haem-containing protein with similarities to the oxygen-binding proteins found in animals.
In soybeans, leghemoglobin helps maintain the low-oxygen environment required by specialised bacteria living within the root nodules. These bacteria convert nitrogen from the atmosphere into forms the plant can use for growth.
While most people have never heard of leghemoglobin, it has been quietly performing this role in nature for millions of years.
Why Does It Look So Convincing?
What makes soy leghemoglobin particularly interesting is that it contains haem, an iron-containing compound also found in animal muscle tissue and blood. Haem is largely responsible for the characteristic colour associated with red meat and plays an important role in the sensory experience of eating meat.
When heated, soy leghemoglobin undergoes changes that resemble some of those seen when meat is cooked. This allows certain plant-based burgers to transition from a reddish appearance when raw to a more browned appearance after cooking.
The result is a product that more closely resembles conventional meat in both appearance and cooking behaviour.
The Remarkable Science Behind It
The process used to produce soy leghemoglobin is arguably just as interesting as the protein itself.
Although soy leghemoglobin occurs naturally in soybean roots, obtaining meaningful quantities directly from plants would be impractical on a commercial scale.
Instead, scientists identified the gene responsible for producing the protein and inserted it into a strain of yeast. The yeast is then grown through large-scale fermentation, producing soy leghemoglobin in quantities suitable for food manufacturing. The protein is subsequently purified and incorporated into selected plant-based meat products.
There is something undeniably fascinating about the process.
Consider the amount of work involved: identifying a protein in soybean root nodules, isolating the relevant gene, engineering yeast to produce it, fermenting it at scale and then incorporating it into a product designed to mimic the appearance and cooking characteristics of meat.
Whether someone views this as an impressive technological achievement or a step away from traditional food systems is largely a matter of perspective. What is difficult to dispute, however, is the extraordinary amount of scientific innovation involved in recreating something that occurs naturally in animal muscle tissue.
Is It Safe?
Soy leghemoglobin has undergone regulatory safety assessment before approval for use in food.
This has included reviews of toxicology data, allergenicity assessments and estimated dietary exposure.
Based on the available evidence, regulatory authorities have concluded that soy leghemoglobin is safe for its intended use in approved food products.
As with any ingredient, ongoing monitoring continues as consumption patterns evolve and additional research emerges.
The Bigger Picture
Whether someone chooses conventional meat, plant-based meat or a combination of both is ultimately a personal decision.
The presence of soy leghemoglobin does not automatically make a product healthier or less healthy. From a nutritional perspective, questions such as protein quality, sodium content, overall nutrient density and the degree of processing are often more important.
While soy leghemoglobin is best known for helping create the colour and some of the sensory characteristics associated with meat, it can also contribute iron to the finished product because it contains haem. The amount will depend on the specific product and serving size, so this is best assessed from the nutrition panel rather than assumed from the ingredient alone.
From a food science perspective, however, soy leghemoglobin is a fascinating example of how biotechnology can be used to replicate some of the sensory characteristics traditionally associated with meat.
The Bottom Line
The red colour seen in some plant-based burgers comes from soy leghemoglobin – short for legume haemoglobin – a naturally occurring soy protein that contains haem, the same iron-containing compound responsible for much of the colour seen in animal foods.
By producing this protein through fermentation, manufacturers can create plant-based products that more closely resemble meat in appearance, flavour and cooking behaviour.
Whether you choose to eat these products or not, the science behind them is undeniably fascinating. It is a remarkable example of the lengths food scientists can go to in order to recreate familiar sensory experiences using entirely different ingredients.
Article written by
Peter Christinson
Certified Practicing Nutritionist
Vive Health – Retail and Clinic Manager
