Associate Professor Trine Kastrup Dalsgaard, Department of Food Science, Aarhus University, is a Steering Committee member in CBIO, the Aarhus University Centre for Circular Bioeconomy. She explains why we should even consider making humans eat proteins from e.g. rye grass, lucerne and grass clover:

- Green protein is a fine source of healthy protein, because the amino acid composition is excellent – it may be even better than soya protein, which is widely used in foods. In addition, we are good at growing grass in Denmark – green grasslands as far as the eye can see, holding great potentials. Further, grass has a positive environmental impact due to the very low nutrient leaching from perennial grasslands. Thus, the surrounding areas of vulnerable water bodies will be obvious areas for producing green crops, which have active roots all year, retain the nutrients and may be used for both feed and foods.

Grass is interesting for food purposes, and not merely as a protein source. Research efforts further focus on processing protein from grasses in order to achieve protein fractions with specific functional properties. This means that the protein can be used as ingredients in different types of foods. The protein abilities to gel, foam or act as emulsifiers are crucial to which types of foods they may be added and help change e.g. the texture of a product. Grass proteins thus become a high-value product; and something to profit from.                                                    

Problematic enzymatic browning

Extracting proteins from grass to be used in the food industry is not quite simple.

Trine Kastrup Dalsgaard explains:

- In relation to extracting proteins we face two overall problems; one of these is that you need to extract the chlorophyll (the green pigment). If the chlorophyll is not removed, it may cause challenges in relation to shelf life and quality as well as consumer preference. Another problem is enzymatic browning of the product, also known it from cut apples or peeled potatoes. This browning is caused by so-called redox enzymes, in green plants the best known it polyphenol oxidase. The enzymatic browning reaction results in crosslinking of proteins with polyhenols, which will impact the digestibility and the absorption of protein in our digestive systems. The browning may also imply that the functional properties of the protein are changed because you change the structure of the entire protein.

However, researchers seem in control of the enzymatic browning, Trine Kastrup Dalsgaard explains, and some promising studies have been accomplished:

- In cooperation with the Department of Animal Science, we carried out rat experiments that demonstrated that it is possible to increase protein digestibility by inhibiting polyphenol oxidase. This will increase protein digestibility, and we further discovered that certain amino acids are protected when the enzyme is inactivated.

Foods are not just foods

Digestibility is a factor to be taken seriously; at the moment focus is on functionality and there are obvious reasons for this: foods are not just foods, and the protein is supposed to be multifunctional, depending on the end product; e.g. a protein drink or meal replacements for sick persons or the elderly.

One of the major potentials of high-value products is the ability to replace part of the animal protein used in high-protein products for e.g. senior citizens with poor appetite or other groups with specific needs. In these instances, it is of vital importance, that the protein has a high solubility and that the amino acid composition fits the target group. If the protein is used in muesli bars or meat alternatives, the binding properties and product texture are important.

Therefore, production processes vary significantly according to the product in question. And in relation to e.g. solubility, the enzymatic browning causes trouble again, and inactivation of the problematic enzyme is essential.

Trine Kastrup Dalsgaard explains:

- Once the enzymatic browning appears, the protein is bound and the solubility is very low. This is a major barrier. We need to inhibit the enzymes, or – alternatively – separate the polyphenols and extract them; but this latter option is not possible in practice, as the reaction happens extremely fast when you either juice or process the green material.

The taste of hay must be removed

We have come a long way regarding the production of protein feed from grass, but not all progress within the feed area can be applied directly to the production of grass protein for foods – for instance, the taste plays a central role in human food products.

Even though most people like the smell of fresh hay – and green is good for your eyes – consumers are not willing to accept the taste of hay or grass nor a greenish colour in foods. - There is a need for biorefining to get rid of the grass taste. When working with foods instead of feed, sensory preferences, how food feels in the mouth, taste and appearance become very important factors, says Trine Kastrup Dalsgaard.

Some way to go yet – and political goodwill is central

Numerous challenges remain, and grass protein in foods is not immediately around the corner, as Trine Kastrup Dalsgaard points out:

- It should be emphasized that we still have a way to go. We may start testing the proteins that we extract today, but they are nowhere near food quality yet. We will get there – we simply need to develop the techniques that we use already. Today, we can easily refine proteins for foods at laboratory scale. This means that we are able to produce food quality protein in small scale experiments, but we still needs to upscale to pilot plant and large-scale production when talking grass protein for foods.

The development of extraction and processing techniques constitute a challenge, as does the financing of these development efforts:

- You may ask which industry should finance this. We are not able to provide an exact date for a final product. Therefore, we might need society efforts to achieve our goals, if we want to be pioneers and leading within this field. And I do believe, that Denmark may be the best and most suitable place as we already have innovation within this field. It will require social pressure and political goodwill, just as we witnessed with the wind power venture.

WANT TO KNOW MORE?

Insights and outlooks on the development of new protein sources for Europe will be the main theme, when Aarhus University hosts Circular Bioeconomy Days: 

Join us for Circular Bioeconomy Days
 

Read more about the research efforts at the CBIO and CiFOOD website