Lucerne biscuits. The Rubisco in this plant could be an attractive substitute for soya proteins in food. It contains all the essential amino acids humans need and is closer to milk proteins.

Because of its ability to fix nitrogen from the air and enrich the soil with this element, lucerne is the biggest forage crop in the world, cultivated on around 32 million hectares. Until now, lucerne has been pressed and dried to produce dry lucerne plus a protein extract (PX), both of which were used in animal feed. Now several years of research have demonstrated that it contains a protein which could be of interest to far more lucrative markets. Rubisco, as it is called, accounts for approximately 2% of the total dry matter fraction of lucerne.

Rubisco helps plants to convert energy from the sun and could profitably replace soya as a source of protein in food. At the moment, almost 80% of the plant proteins in food come from soya, but none of them covers humans' nitrogen and amino acid requirements. By contrast, Rubisco contains all the essential amino acids which humans need and is closer to milk proteins. 'And production of plant proteins is known to be infinitely more profitable than production of animal proteins,' points out Olivier Pauwels from Alfa Laval France, 'since the return is 10 to 100 times higher, depending on the plant.'

Rubisco also has foaming and emulsifying properties which could be harnessed not only in food but also in cosmetics and detergents.

Finding new uses for lucerne

In response to lucerne's loss of competitiveness against rival products (such as oil seed cakes) and to falling European subsidies, the lucerne industry had to diversify. 'This is why we developed an advanced technology for fractionation of lucerne, capable of extracting Rubisco. At the time, the idea was to extract a marketable fraction and to offer the byproduct in the animal feed industry, our line of business,' explains Bernard Petin, manager of France Luzerne and coordinator of the Fralupro project.

The project, which is supported by the European Union, began in 1997 when France Luzerne and its five partners set out to test the technical and economic viability of the pilot process for large-scale production. 'Moving on to the next stage posed a real scaling-up problem,' recalls Charles Thémistocle from the Centre de Valorisation des Glucides et des Produits Naturels, 'as the pilot plants had to be adjusted to make them compatible with large-scale production.'

Specific constraints

In particular, the challenge was to work on a fresh juice rather than on a protein extract, such as the grain protein produced from soya. 'Technically, this meant working rapidly and continuously to avoid all the metabolic reactions likely to occur in fresh juices, particularly oxidation,' the project coordinator added. 'What is more, although small-scale production of a juice containing less than 0.5% insoluble matter is relatively easy, maintaining this rate when the capacity is scaled up is by no means certain,' admits Charles Thémistocle. 'It then becomes difficult to produce a colourless and, above all, tasteless protein.'

The same scaling-up problems also apply to temperature control of the preparation, its pH and the capacity of the installation to adapt to a raw material with a dry matter content which fluctuates widely, depending on the season and weather conditions.

Another imperative is to make the quantum leap from animal feed to human food. As Olivier Pauwels says, 'It is not just a question of extracting the raw materials, but also of keeping them wholesome and digestible.' Care must also be taken to avoid extracting some of the products in just a few minutes but leaving the rest for hours in the installations, where there could be a risk of microbial contamination.

Technological innovation

This example of European cooperation culminated in the construction of a demonstration unit operating on the site of France Luzerne. While the original pilot unit was able to produce 6 kg or 7 kg of protein an hour, the new production unit manages between 35 kg and 50 kg in the same time. In the long term, the France Luzerne plant could produce 1 200 tonnes of Rubisco a year, at almost the same cost as soya. 'The extraction process is a complete innovation, since it is the first to convert the plant directly into a protein extract for human consumption,' Bernard Petin says proudly.

Major outlets will open up as soon as the food safety committees give the go-ahead to put Rubisco on the market as a food ingredient. Another attraction of this innovation, as the debate about genetically-modified organisms continues, is that this ingredient is of clearly defined composition and clearly identified origin - which is not always the case with soya imported into Europe.

Alongside the technical aspects, the Fralupro project also provided an opportunity to explore the potential markets for Rubisco, opening the way to development of different industrial applications. In the future, this new fractionation technology for lucerne could be used to extract other plant proteins with high-value applications in pharmaceuticals and cosmetics in particular.