Extracting high-value Rubisco protein from tomato leaves

Harvesting food crops results in the yearly production of around 40 tonnes (for sugar beet) to 50 tonnes (for tomatoes) of crop residues per hectare. These residues are composed of leaves and stems. The leaves are either ploughed back into the soil as fertiliser or are composted. They do, however, contain high-quality proteins that could be used for human consumption – crucial when we want to ensure a sustainable food supply for our growing global population, and to help accelerate a transition towards a more plant-based diet in developed countries.

An example of such a protein is rubisco, or ribulose-1,5-biphosphate carboxylase oxygenase. This protein is neutral in its aroma, colour and flavour, with a well-balanced amino acid composition. Its superior gelation properties make it very useful for processing into meat substitutes and plant-based dairy alternatives, for example to provide a ‘bite’ or improved mouthfeel.

Removing toxins

In the project ‘Technology development for healthy and safe protein during biorefinery’ scientists from Wageningen Food & Biobased Research investigated whether an existing method of extracting rubisco from sugar beet leaves could be used for isolation of this protein from tomato leaves. They wanted to find out whether they could remove the toxin hydroxytomatine.

High-quality protein powder

The experiments, carried out on a pilot-scale, delivered a high-value protein powder, which was free of toxins. The researchers expect the same method could also be suitable for extracting rubisco from the leaves of other food crops. The leaves of potato and cassava plants, for example, which also contain toxins, making them currently unsuitable for direct consumption.

Scaling up

The researchers hope to work with the private sector to further develop the technology aiming to apply it on an industrial scale. That could mean working with greenhouse horticulture businesses, or businesses that use plant-based proteins as inputs. These might include producers of dairy and meat substitutes.

Wageningen University & Research has been carrying out research into efficient, economically viable protein extraction from agricultural residues for more than 10 years. This research involves process technologists and biochemists working closely with experts in plant breeding and plant physiology.