“Its nutritional value is also very good. “You can also use starch or methylcellulose, but the product will then be high in carbohydrates, which is often not what you want.” According to Bruins, rubisco’s gelling quality is what makes it really appealing to food producers. “The only other plant-based protein that can make a good gel is potato protein,” says Bruins. Producers will often add egg as a way of achieving a particular structure, which might be helpful if it’s to be used in meat substitutes or plant-based dairy products. “That’s not a quality you typically find in many other plant-based proteins, such as soy,” says Bruins. One advantage of rubisco protein is that it can be easily processed into a gel. Watch this video about protein extraction from leaves And just think of the quantity of leaves generated as a result of greenhouse horticulture.” The best case scenario is that they end up in a compost heap. At present, tomato leaves are cut off and just swept up into a pile. “There’s such an abundance of leaves on our planet, and ultimately we’d like to make use of every resource available to us. But Bruins hopes to see it being rolled out more widely. The method is currently being used by Cosun, a beet producer, to extract protein from sugar beet leaves. They’ve now also done tests to see if this process prevents toxins ending up in the final product, making it safe to eat. Bruins and her colleagues had previously already developed a patented process for extracting protein from leaves. It’s readily soluble and not attached to anything else in the cell, so you can squeeze it out of the leaf.” But the disadvantage to tomato leaves is that they also contain toxins. “This protein is essential for capturing and storing CO2 from the atmosphere. “At least a quarter of all the protein in the leaf is rubisco,” says Marieke Bruins, Senior Scientist in Protein Technology. The leaves of all plants, such as those of sugar beet or tomato plants, contain the protein rubisco. Residues might be composted or, at best, used as animal feed. There is value in high-protein crop residues, but this value is often not extracted and used in the food chain.

Here are a few examples of projects in which WUR is working on circular protein production: Any protein sources unsuitable for human consumption could be upcycled using, for example, micro-organisms or insects. In an optimal food system, humans and animals would not be competing for food, and any resources suitable for direct consumption would indeed be used as food.

Circular systems are an example of how this might be achieved.

Wageningen University & Research is looking for ways to increase the availability, diversity and acceptance of existing and emerging sources of protein. A protein transition is essential if we are to ensure a sustainable diet for everyone on the planet in future. The way we produce and consume protein today places an unsustainable burden on our natural resources, and the problem is getting worse as demand for animal-based protein grows. The production of protein from tomato leaves, fungi and insects is one example of how this might be achieved. Ideally, this would be done in a way that avoids competition between humans and animals for their food. WUR researchers are looking at how we can produce proteins in a sustainable and circular manner.

Tomato 2 leaves wageningen