Can fermentation increase the availability of iron in meat analogues?

The interest in plant-based meat-like products, known as meat analogs, is high and growing. However, there are some nutritional challenges with today's meat analogs, such as an often high content of the antinutrient phytate that makes iron less available to the body. Fermentation is an interesting possibility to reduce the phytic acid content.

For health reasons, we should limit the intake of red meat to 350 grams per week, according to the new Nordic Nutrition Recommendations (NNR2023), launched in June this year. There is no reliable information on how much meat we eat in Sweden, but according to estimates from Swedish Meat, based on data from the Swedish Board of Agriculture and the Swedish National Food Agency, in 2022 we ate about 530 g of red meat per week. This is an average for the entire population, and we know that some groups eat more than others, for example men generally eat more red meat than women. This means that some groups may have more reason than others to reduce their intake of red meat, from a health perspective. Red meat is also the dietary factor with the highest climate impact, together with dairy products. This further strengthens the need to limit our overall consumption of red meat.

Meat analogues - from texture to nutritional quality

As a response to the increasing focus on reducing meat consumption, plant-based alternatives that resemble meat, known as meat analogues, have rapidly emerged in recent years as a new category of food products on store shelves. These products are often based on protein concentrates or protein isolates from legumes, such as soy or pea. Meat analogues offer alternatives for consumers who want to reduce or avoid meat, but still appreciate the taste, texture and shape of traditional meat products, such as burgers, mince, fillets, sausages. The development of products in this segment has been very fast, with a strong focus from research and development on creating attractive products based on texture, taste and color. Recently, however, the nutritional quality of meat analogs has come under increasing scrutiny, and will probably be a crucial factor in the success of future generations of meat analogs. This may involve, for example, creating meat analogs with better fat quality, lower salt content and higher fiber content.

The Iron Challenge

A key nutritional challenge for plant-based meat analogues is their iron content and the availability of this iron to the body. This challenge is partly due to the fact that plant-based raw materials do not contain so-called heme iron, which is only found in meat and is better absorbed by the body than free iron. The challenge is further compounded by the presence of the antinutrient phytate, which effectively binds iron and zinc, for example, preventing the minerals from being absorbed by the body. Since meat is an important source of iron in the Swedish diet, the iron intake of people who replace red meat with meat analogs may be too low. A Swedish study from Chalmers University of Technology has shown a lower iron uptake from meat analogs compared to meat-based alternatives. This is problematic because we know that iron intake is already at risk of being low in many groups, not least in young people and women, who also have a higher iron requirement. Therefore, there is currently a great deal of interest in finding solutions, such as new process technologies, that result in the breakdown of phytate and increase the availability of iron in meat analogs. Phytate with more than four phosphate groups binds iron very efficiently, the aim of the processing should therefore be a degradation to phytate molecules with only one or two phosphate groups.

Fermentation a possible solution

Fermentation is an interesting possibility to reduce the amount of phytate in plant-based raw materials. In addition, fermentation can be beneficial by reducing the amount of oligosaccharides, which are present in legumes and can cause stomach pains in sensitive people. Another benefit of fermentation could be a positive impact on the texture and taste of the final product.

- The ability to degrade phytate is present in several microorganisms, but can differ greatly between microorganisms. Much remains to be investigated regarding the potential of different microorganisms for improving the nutritional quality of meat analogs. "In addition to having the ability to degrade phytate, the microorganisms also need to be able to grow and multiply on the material, such as a protein, in order to carry out the degradation," says Karin Bjerre, researcher at RISE.

- There are several examples of successful experiments in research. In the Vinnova-financed project Like:meat, we showed in lab experiments and pilot scale that several different microorganisms could degrade phytate in pea protein. In order to achieve the desired degree of phytate degradation, we may need to work further on optimizing cultivation conditions and also look at different combinations of microorganisms," says Karin Bjerre.

How do you know if the iron is available?

Many factors influence how well the iron in a particular food is absorbed by the body. To know for sure how available the iron in a food product is to the body, human studies are needed. Some cell models and experimental in vitro models can also be used to give indications of the availability of iron. In foods with known high levels of phytate, such as whole grains and legumes, a rough theoretical estimate can also be made by looking at the ratio of the phytic acid content to the iron content at the molar level. To know how many moles of phytate and iron the product contains, both need to be chemically analyzed. For a more reliable assessment, phytate should be analyzed by a method that allows to distinguish between phytate forms with different numbers of phosphate groups.