Using fermentation to boost plant proteins
As the plant-based food transition gains steam, manufacturers are faced with challenges to bring analogue foods closer to nutritional parity with the dairy and meat versions, such as the challenge of increasing protein without creating ‘negative’ sensory issues.
Herwig Bachmann, Expertise Group Leader Fermentation at NIZO, explains how innovations in the age-old technology of fermentation can help overcome these challenges, enabling the addition of new ingredients into plant-based products.
Why are manufacturers looking to add plant protein to ‘analogue’ foods?
Herwig Bachmann: If you look at the ingredient list and nutritional information printed on the packaging of food analogues, such as a plant-based cheese, you will see that many of these products contain often only between 0-1 percent protein. Their ingredients are essentially starch, fat and a bit of flavour. Manufacturers want to improve on these plant-based foods, including increasing their nutritional value, by adding a plant-based protein, for example.
Sometimes, they have a specific plant protein substrate they want to use. Sometimes, there is a specific functionality they want to add, and they need to find the best substrate for that purpose. Sometimes, they are looking for one substrate that they can use in a whole range of vegan products. So the starting points can be very different.
Comparison of nutritional information from the labels of a dairy cheddar and 4 cheese analogues on the market today
Why is it difficult to add plant-proteins into foods?
HB: Plant proteins can add ‘off’ flavours to a food – some of which have been described as ‘grassy/beany’, ‘cardboard’ and even ‘wet socks’. Furthermore, they don’t automatically provide the texture people expect from a cheese, yoghurt, etc. They can be sensitive to heat sterilisation, which may destroy their functionality. Yet, since many of the proteins come from foods that are literally sourced close to the soil, they can be contaminated with spores from different organisms (fungal, bacterial, etc.), which can survive pasteurisation.
Another challenge is the large number of potential plant proteins, combined with our unfamiliarity with them. We have millennia of experience working with dairy proteins, for example, but that is only one substrate. Each plant protein presents its own challenges.
What is fermentation, and why is it an attractive technology for food manufacturing?
HB: In fermentation, live micro-organisms perform a metabolic process to create enzymes that change the chemistry of a food ingredient or product. This results in products with different flavours, textures and nutrients. It’s a very old technology that we understand quite well.
Fermentation is artisanal and natural, and can be used for a broad range of functionalities. Complex wild fermentation is also very cheap to culture. Take the example of sourdough culture, which requires only flour and water. Yet it’s a very stable way of converting a plant-based substrate: you hardly ever get any contamination. It adds flavour and texture, it increases digestibility, because it pre-digests certain carbohydrates. It leavens the dough, and adds acid which aids in preservation.
Selected strains or tailored cultures can be used to bring specific functionalities such as flavour into a product through fermentation. At NIZO, for instance, we have a culture collection with over 4,000 strains. On an industrial level, this means that you can really control the process, by selecting a strain, or combination of strains, that provides desired functionalities.
How do you use fermentation to solve the challenges of adding plant proteins to foods?
HB: Traditional fermentation has been done on ‘complete’ plant materials such as soy beans or vegetables, to create products like tempeh or sauerkraut. But the ability to use fermentation on protein isolates and concentrates has been a critical, and more recent, development.
This has enabled new ingredients to be brought into products where producers would like to move towards nutritional parity. Some fermentation strains, for example, eliminate hexanal, which is the molecule that causes that grassy, beany flavour. Others can alter texture. Imagine you want to produce a vegan cream cheese using plant proteins, but you are facing a challenge in creating the desired texture: maybe its grainy, or too hard or dry. Fermentation can improve the texture and the mouthfeel through exopolysaccharide (EPS) production or hydrolytic breakdown of proteins. And combining fermentation with pasteurisation can solve the challenge I described earlier of heat-resistant spores.
What are the specific challenges in fermenting plant proteins?
HB: There are a broad variety of strains that can be used for fermentation, and many possible plant protein substrates, and they all interact with each other differently. So a lot of trial and error is involved in determining which strain will provide the desired functionality in which substrate. A strain that smooths texture in a product with a pea protein might not do the same with an oat protein.
In one study, we combined one strain with 15 different plant proteins. With some of the proteins, the strain grew well on its own. In others, we had to add additional nutritional sources – sugar, yeast extract, etc. – to see growth. But for one plant protein, no matter what we added, the strain would not grow – meaning there is something in that specific substrate that inhibits that particular strain from growing.
Understanding strains and substrates is thus very important to enable manufacturers to add plant proteins to foods on a consistent basis. We are taking part in several consortia that are working to increase knowledge in this area, to reduce the amount of trial and error, and more precisely target strains and substrates based on what manufacturers want to achieve. One route towards this goal is a combination of microbial genome sequencing and artificial intelligence for the prediction of strain functionalities.
How will developments in fermentation further support the protein transition?
HB: Although fermentation is such an old technology, there is a lot of innovation in the sector, which I believe will play a big role in the future of the protein transition. The ‘Bio-purification of plant proteins’ consortium, which is led by NIZO, is exploring novel ways to use fermentation technology to remove off-flavours and other unwanted characteristics in various plant proteins and isolates.
The concept is to eliminate molecules that create off-flavours or anti-nutritional compounds from the plant proteins, but without producing the high lactic acid levels of a true ‘fermentation’. This should allow the plant-based food industry to develop innovative bio-purification processes for manufacturing new or improved plant-based ingredients and food products. The availability of such high-quality plant-based products – potentially with fewer additives – will give consumers greater choice of healthy food options.