Researchers of Wageningen University are the first in the world to extract high-value Rubisco protein from tomato leaves, which is one of the major residue streams of greenhouse horticulture. They used a method similar to those they had previously developed for extracting Rubisco from other crop residue streams.
The application of this process on a large scale will increase the availability of plant-based proteins, contributing to a sustainable food supply for the world's growing population. It will also aid in the acceleration of the transition to a more plant-based diet in developed countries.
The pilot study was based on an extraction method for Rubisco from sugar beet leaves. The researchers wanted to see if they could use this method to remove the toxin hydroxytomatine from tomato leaves as well. As a result, a high-value protein powder free of toxins was created.
The same technique could be used to extract Rubisco from the leaves of other food crops. Toxins are also present in the leaves of potato and cassava plants, making them unfit for direct consumption, as are tomato leaves.
"Our method filters out components smaller than the protein we want to extract, which includes many toxins," says project leader Marieke Bruins, senior scientist in protein technology at Wageningen University & Research. "Our research shows that by making better use of what you already have, you can achieve significant gains in sustainability."
The researchers hope to collaborate with the private sector to further develop the technology so that it can be used on a large scale. "This could imply collaborating with greenhouse horticulture companies or companies that use plant-based proteins as inputs. These could include dairy and meat substitute manufacturers," says Bruins.
Harvesting food crops results in a yearly production of crop residues ranging from 40 tonnes (for sugar beets) to 50 tonnes (for tomatoes). The residues are made up of leaves and stems. When compared to extracting protein for human consumption, the leaves are either ploughed back into the soil as fertiliser or composted.
Rubisco, or ribulose-1,5-biphosphate carboxylase oxygenase, is an essential photosynthesis enzyme. As a result, the protein can be found in every leaf of every green plant on Earth, and in large quantities. Rubisco has a neutral aroma, colour, and flavour in its pure form, as well as a good balance of essential amino acids. It also has excellent gelation properties.
This makes Rubisco an excellent protein for incorporating into meat substitutes and plant-based dairy alternatives, for example, to provide a firm 'bite' or improved mouthfeel. It's also a good egg substitute in baked goods.
For more than a decade, Wageningen University & Research has been conducting research into efficient, economically viable protein extraction from agricultural residues. Process technologists and biochemists collaborate with plant breeding and physiology experts on this project.
