News - June 9, 2010

Oranje boven

To call it orange madness is perhaps a little too far-fetched, but several Wageningen researchers do live out their kind of orange fever. A round-up of orange research in Wageningen UR.
By Roelof Kleis, Albert Sikkema and Hans Wolkers

The tiger lily on a stamp
Nature doesn't applaud orange
The tiger lily. It doesn't take Joop Schaminée of Alterra long to think of an orange plant. Unfortunately, its flower is extremely rare.
The Dutch nature doesn't applaud orange. Schaminée can call to mind only a few species with orange flowers. The Orange Hawkweed, naturally. What about the Scarlet Pimpernel? Oh come on, let's call it orange too despite its name. And of course, the tiger lily or orange lily. The Lilium bulbiferum subsp. Croceum is without doubt the most beautiful indigenous orange plant. But chances are slim that anyone knows it, because it is extremely rare. Philatelists are probably the only people who would recognize it: the plant was honoured in 1994 on a stamp.
It wasn't like this in the past. The tiger lily was then just as prominent in cultivated land as the blue cornflower or the red corn poppy. 'But if anything has been threatened, it's farmland flora', says Schaminée. 'The Dutch farmland used to have an unimaginable quantity of unusual and rare plants. This diversity has disappeared because of drainage, intensification and expansion in agriculture. The tiger lily has suffered an enormous setback as a result.
Controlling orange at atomic level
The orange-red part of the light spectrum supplies the most energy. The Laboratory of Organic Chemistry is working on new materials which can capture that particular part of light.
Mention solar cells, and an image of big flat panels on the rooftop comes to mind. Indeed, wider applications aren't in the picture yet. But that's going to change. As far as Prof. Han Zuilhof of Organic Chemistry is concerned, that has already happened. His group is hard at work with new materials which can capture light. These materials have to be pliable and easily fitted into any desired shape. Plastics.
Plastic is the carrier in the new generation solar cells. Since light is captured by organic materials, the researchers closely examined how nature works, and found the solution in carotene, the colourant in carrots. 'We have produced a whole range of substances which resemble carotene', informs Zuilhof. 'By adding or subtracting an item, we can accurately control the wavelength of the light which we want to capture.' The chemist can thus control orange at atomic level. 'The national coach of Oranje can take a leaf out of this book', jokes Zuilhof. The big advantage of organic light absorbers is that they can be built easily into plastic. 'However, they break down rapidly due to photochemical dissociation', says Zuilhof. That happens to all organic materials. If the light absorbers were to remain intact, we would need to resort to inorganic materials.' The inorganic component in this instance is silicon, the basic material for the traditional solar cell. But it is here used in a new form: silicon nanoparticles. These particles can be made to an exact size, with a very thin outer organic coating about one nanometre thick. This nanojacket has to prevent oxidation. PhD student Umesh Chinnaswamy makes tiny silicon balls two to five nanometres in size. Zuilhof: 'Each of these captures a small part of the spectrum, depending on its size. 'The size of the particle is therefore a parameter which you can control. 'The bigger the particle, the redder the absorption. Orange lies halfway. We are working on it now. We haven't got red at our fingertips yet.
In applications, the nanoparticles have to be housed in plastic too. It's just possible that mobile phones will in future be run on such plastic solar cells. Zuilhof: 'Organic material would be used if a long life span isn't required, and inorganic material, if it has to be longlasting.'
'Organic light absorbers can be built easily into plastic'
Paint with calendula
Robert van Loo of Plant Research International is doing research on the marigold, the Calendula officinalis. This plant owes its orange colour to the beta carotene in the flowers. Calendula is well-known because of healing creams and baby oil, but this is not why Van Loo finds the flower interesting. He grows the marigold for its pure seed oil. The high drying properties of calendula oil with its orange glow makes it suitable for use in paints. The company Calendula Oil b.v., a spin-off from Wageningen UR, has developed a production and retail network for calendula oil for the paint industry. The marigold has another surprising usage. The flowers are also added to chicken feed and this produces nice orange egg yolks.

Orange is more delicious
The orange carrot which is so common today has its origins in the sixteenth century in the Netherlands. Before that, carrots had all sorts of colours, varying from white and yellowish green to purplish red. Those colourful carrots were brought into the Netherlands via Spain from Turkey and Afghanistan. Two developments have led to the modern carrot as we know it today. The first was the discovery of a sweeter carrot with a high sugar content, which tasted better. At the same time, beta carotene increased in the carrot, which also accounted for its colour. Thus, orange it has become and better is its taste.
The modern carrot also evolved because a shorter carrot was developed for planting in trays. Among the pioneering species were the 'Utrecht Bak' and the 'Amsterdam Bak', which are still around today.

The tiger lily is classified in Schaminée's Atlas of Plant Communities under the Lamb Succory types, plants encountered long ago in the rye fields by the old ash trees. 'In a few places in our country, people are trying to bring back the old ash trees, such as in the Drenthe museum village Orvelte.' The tiger lily is featured in Schaminée's book Midden-Drenthe, getekend in het zand. This work from 2006 is an appeal to recognize and to restore characteristic local features in the nature. 'In the province of Middle Drenthe, this could be the tiger lily. It belongs there from times past, but you don't see it anymore now. We found the flower only in the gardens of people who have at some time transplanted it from nature.'
Schaminée disapproves of the uniformity which crops up everywhere. 'Every region had its own farmland flora and varieties in the past. Those complex co-existences which have grown over the centuries have almost completely disappeared. Singularity, that's what I would like to draw attention to.
'It grows only in people's gardens'

Mould changes peanut mush into delicacy
'Really delicious', says food microbiologist and fermentation expert Rob Nout. He points to a photograph with bright orange moulds sprouting against an indescribable background.
The background turns out to be remains of crushed peanuts. This is a food item which originates from Indonesia and is known as 'oncom'. The mould Neurospora intermedia plays a vital role in the making of oncom. 'A block of crushed peanut remains is grafted with mould filaments, and within a day, the peanut mush is overgrown with moulds', Nout explains. 'The mould is then white in colour, but if the block is exposed to light, it turns orange within several hours.' The mould ferments the bland peanut mush into a food item highly popular in Indonesia. 'During the conversion process, the texture changes, and the taste as well', says the fermentation expert. 'The orange mould makes the mush easy to chew and converts peanut oil remains into all sorts of bonds which give a sharp nutty flavour.

Turning bright orange from stress
The alga Dunaliella salina has a peculiar characteristic. If it encounters stress, it changes colour: from bright green to bright orange. This is caused by beta carotene, the colour substance in carrots.
'Normally, this alga consists of only half a percent of beta carotene', explains Rene Wijffels, professor of Bioprocess Technology. But if you put Dunaliella under stress, for example, by giving it a lot of light, this percentage increases to ten to fifteen percent. The beta carotene in fact protects the alga against harmful substances which crop up because of too much light.' The stressed alga not only turns a beautiful orange colour, but also produces more fat. The fat is stored in the cell as tiny globules and is an excellent base for bio-diesel. 'Initially, we thought that we could 'milk' the alga without killing the alga cell by using a solvent to extract carotene and fat', says Wijffels. 'The solvent however caused spontaneous cell death. Milking was therefore out of the question. But production of beta carotene goes on because growth compensates for cell death.'
The nice thing about Dunaliella, according to Wijffels, is that the orange colouring makes the stress process highly visible. 'During practicums, we ask students to think of ways to enable this alga to make as much carotene as possible. They then have to put their idea into practice. The result is a wonderful colour palette depending on the success of the chosen method.
'The orange colouring makes the stress process highly visible'

Orange cassava set to conquer Africa
Food researcher Inge Brouwer is a football fan. 'I go to the matches of Oranje frequently, in orange attire.' Last week, she was at the international friendly match between the Netherlands and Ghana. Bearing her favourite colour, the orange cassava is one of the food substances which she will introduce into Africa in her role as researcher.
Brouwer is the research leader of the European Union programme Instapa, which develops strategies to improve staple food in sub-Sahara Africa. She is currently working on the orange cassava in Kenya. The cassava is enriched with beta carotene, which is converted into vitamin A in the cassava. This vitamin is good for the eyes and increases resistance.
'We have grown a hundred cassava varieties in Kenya with different natural concentrations of beta carotene. We cross-breed a Brazilian variety with local African varieties to improve the beta carotene content. A concentration of fifteen micrograms of beta carotene per gram of cassava is necessary to achieve a health effect. Among the hundred varieties, we have found one with 23 micrograms per gram of cassava. It is reddish orange in colour. We have also found two varieties with above twenty micrograms.'
Later on, Brouwer wants to offer the orange cassava to the local population. 'We have come to know that they don't object to orange cassava and they are willing to pay more for it if they are clearly told what the health benefits are.' She first wants to do a nutrition test with Kenyan children who will be fed orange cassava for six months. 'We will determine their vitamin-A deficiency at the beginning of the test, and measure their vitamin-A status again at the end.'
Tests are also being carried out to breed orange maize in the programme Harvest Plus of the international agriculture institutes of the CGIAR. Besides vitamin A, the researchers also want to achieve a higher concentration of zinc, iron, iodine and folic acid in plants or food substances. 'These are the big five micronutrients in food. A lack of these will give rise to more problems from diseases and less cognitive development', says Brouwer.

The Orange List
The Centre for Genetic Resources (CGN) compiles the 'Orange List' (Oranje Lijst) of vegetable crops. The list comprises the names of various vegetable crop varieties cultivated in the Netherlands between 1850 and 1940. Most of the varieties have been replaced by commercial high yield varieties.
The list was needed to establish the varieties which belong to the Dutch bio-cultural inheritance and therefore require protection. Currently, there are 2830 old varieties on this list, many of which form the basis for current vegetable varieties. About 750 old potato varieties are on the list, including the Schoolmeester, the Zeeuwse Blauwe and the Berlikumer Geeltje. Of the potato varieties which were cultivated up to the Second World War, seventy are still available. In addition, the list comprises many old varieties of the pea, bean, lettuce, onion, shallot, leek, endive, carrots and cabbage. About a quarter of the old varieties are not available anymore. Items on the Orange List are therefore becoming rare. In any case, the list is incomplete. New vegetable crops are being added to it. More information can be found on