Reading Passage 1 -Talc Powder

Peter Rrigg discovers how talc from Luzenac’s Trimouns in France find its way into food and agricultural products—from chewing  gum to olive oil.

High in the French Pyrenees, some 1,700m above see level, lies Trimouns, a huge deposit of hydrated magnesium silicate – talc to you and me. Talc from Trimouns, and from ten other Luzenac mines across the globe, is used in the manufacture of a vast array of everyday products extending from paper, paint and plaster to cosmetics, plastics and car tyres. And of course there is always talc’s best known end use: talcum powder for babies’ bottoms. But the true versatility of this remarkable mineral is nowhere better displayed than in its sometimes surprising use in certain niche markets in the food and agriculture industries.

Take, for example, the chewing gum business. Every year, Talc de Luzenac France—which owns and operates the Trimouns mine and is a member of the international Luzenac Group (art of Rio Tinto minerals)—supplies about 6,000 tones of talc to chewing gum manufacturers in Europe. “We’ve been selling to this sector of the market since the 1960s,”says Laurent Fournier, sales manager in Luzenac’s Specialties business unit in Toulouse. “Admittedly, in terms of our total annual sales of talc, the amount we supply to chewing gum manufacturers is relatively small, but we see it as a valuable niche market: one where customers place a premium on securing supplies from a reliable, high quality source. Because of this, long term allegiance to a proven suppler is very much a feature of this sector of the talc market.”Switching sources—in the way that you might choose to buy, say, paperclips from Supplier A rather than from Supplier B—is not  a easy option for chewing gum manufacturers,”Fournier says. “The cost of reformulating is high, so when customers are using a talc grade that works, even if it’s expensive, they are understandably reluctant to switch.”

But how is talc actually used in the manufacture of chewing gum? PatrickDelord, an engineer with a degree in agronomics, who has been with Luzenac for 22 years and is now senior market development manager, Agriculture and Food, in Europe, explains that chewing gums has four main components. “The most important of them is the gum base,”he says. “It’s the gum base that puts the chew into chewing gum. It binds all the ingredients together, creating a soft, smooth texture. To this the manufacturer then adds sweeteners, softeners and flavourings. Our talc is used as a filler in the gum base. The amount varies between, say, ten and 35 per cent, depending on the type of gum. Fruit flavoured chewing gum, for example, is slightly acidic and would react with the calcium carbonate that the manufacturer might otherwise use as a filler. Talc, on the other hand, makes an ideal filler because it’s non-reactive chemically. In the factory, talc is also used to dust the gum base pellets and to stop the chewing gum sticking during the lamination and packing process,”Delord adds.

The chewing gum business is, however, just one example of talc’s use in the food sector. For the past 20 years or so, olive oil processors in Spain have been taking advantage of talc’s unique characteristics to help them boost the amount of oil they extract from crushed olives. According to Patrick Delord, talc is especially useful for treating what he calls “difficult” olives. After the olives are harvested-preferably early in the morning because their taste is better if they are gathered in the cool of the day – they are taken to the processing plant. There they are crushed and then stirred for 30-45 minutes. In the old days, the resulting paste was passed through an olive press but nowadays it’s more common to add water and centrifuge  the mixture to separate the water and oil from the solid matter. The oil and water are then allowed to settle so that the olive oil layer can be decanted oft and bottled. “Difficult” olives are those that are more reluctant than the norm to yield up their full oil content. This may be attributable to the particular species of olive, or to its water content and the time of year the olives are collected—at the beginning and the end of the season their water content is often either too high or too low. These olives are easy to recognize because they produce a lot of extra  foam during the stirring process, a consequence of an excess of a fine solid that acts as anatural emulsifier. The oil in this emulsion is lost when the water is disposed of. Not only that, if the waste water is disposed of directly into local fields—often the case in many smaller processing operations—the emulsified oil may take some time to biodegrade and so be harmful to the environment.

“If you add between a half and two percent of talc by weight during the stirring process, it absorbs the natural emulsifier in the olives and so boosts the amount of oil you can extract,”says Delord. “In addition, talc’s flat, ‘platy’ structure helps increase the size of the oil droplets liberated during stirring, which again improves the yield. However, because talc is chemically inert, it doesn’t affect the colour, taste, appearance or composition of the resulting olive oil.”

If the use of talc in olive oil processing and in chewing gum is long established, new applications in the food and agriculture industries are also constantly being sought by Luzenac. One such promising new market is fruit crop protection, being pioneered in the US. Just like people, fruit can get sunburned. In fact, in very sunny regions up to 45 percent of atypical crop can be affected by heat stress and sunburn. However, in the case of fruit, it’s not so much the ultra violet rays which harm the crop as the high surface temperature that the sun’s rays create.

To combat this, farmers normally use either chemicals or spray a continuous fine canopy of mist above the fruit trees or bushes. The trouble is, this uses a lot of water—normally a precious commodity in hot, sunny areas—and it is therefore expensive. What’s more, the ground can quickly become waterlogged.” So our idea was to coat the fruit with talc to protect it from the sun,”says Greg Hunter, a marketing specialist who has been with Luzenac for ten years. “But to do this, several technical challenges had first to be overcome. Talc is very hydrophobic: it doesn’t like water. So in order to have a viable product we needed a wettable powder—something that would go readily into suspension so that it could be sprayed onto the fruit. It also had to break the surface tension of the cutin (the natural waxy, waterproof layer on the fruit) and of course it had to wash off easily when the fruit was harvested. No-one’s going to want an apple that’s covered in talc.”

Initial trials in the state of Washington in 2003 showed that when the product was sprayed onto Granny Smith apples, it reduced their surface temperature and lowered the incidence of sunburn by up to 60 per cent. Today the new product, known as Invelop Maximum SPF, is in its second commercial year on the US market. Apple growers are the primary target although Hunter believes grape growers represent another sector with long term potential. He is also hopeful of extending sales to overseas markets such as Australia, South America and southern Europe.

In 1476, the farmers of Berne in Switzerland decided there was only one way to rid their fields of the cutworms attacking their crops. They took the pests to court. The worms were tried, found guilty and excommunicated by the arch­bishop. In China, farmers had a more practical approach to pest control. Rather than relying on divine intervention, they put their faith in frogs, ducks and ants. Frogs and ducks were encouraged to snap up the pests in the paddies and the occasional plague of locusts. But the notion of biological control began with an ant. More specifically, it started with the predatory yellow citrus ant Oeco-phylla smaragdina, which has been polishing off pests in the orange groves of southern China for at least 1,700 years. The yellow citrus ant is a type of weaver ant, which binds leaves and twigs with silk to form a neat, tent-like nest. In the beginning, farmers made do with the odd ants’ nests here and there. But it wasn’t long before growing demand led to the development of a thriving trade in nests and a new type of agriculture – ant farming.

For an insect that bites, the yellow citrus ant is remarkably popular. Even by ant standards, Oecophylla smaragdina is a fearsome predator. It’s big, runs fast and has a powerful nip – painful to humans but lethal to many of the insects that plague the orange groves of Guangdong and Guangxi in southern China. And for at least 17 centuries, Chinese orange growers have harnessed these six-legged killing machines to keep their fruit groves healthy and productive.

Citrus fruits evolved in the Far East and the Chinese discovered the delights of their flesh early on. As the ancestral home of oranges, lemons and pomelos, China also has the greatest diversity of citrus pests. And the trees that produce the sweetest fruits, the mandarins – or kan – attract a host of plant-eating in­sects, from black ants and sap-sucking mealy bugs to leaf-devouring caterpil­lars. With so many enemies, fruit growers clearly had to have some way of pro­tecting their orchards.

The West did not discover the Chinese orange growers’ secret weapon until 1 the early 20th century. At the time, Florida was suffering an epidemic of citrus canker and in 1915 Walter Swingle, a plant physiologist working for the US f Department of Agriculture, was sent to China in search of varieties of orange that were resistant to the disease. Swingle spent some time studying the citrus orchards around Guangzhou, and there he came across the story of the culti­vated ant. These ants, he was told, were “grown” by the people of a small village nearby who sold them to the orange growers by the nestful.

The earliest report of citrus ants at work among the orange trees appeared in a book on tropical and subtropical botany written by Hsi Han in AD 304. “The people of Chiao-Chih sell in their markets ants in bags of rush matting. The nests are like silk. The bags are all attached to twigs and leaves which, with the ants inside the nests, are for sale. The ants are reddish-yellow in colour, bigger than ordinary ants. In the south, if the kan trees do not have this kind of ant, the fruits will all be damaged by many harmful insects, and not a single fruit will be perfect.”

Initially, farmers relied on nests which they collected from the wild or bought in the market where trade in nests was brisk. “It is said that in the south orange trees which are free of ants will have wormy fruits. Therefore, people race to buy nests for their orange trees,” wrote Liu Hsun in Strange Things Noted in the South in about 890.

The business quickly became more sophisticated. From the 10th century, coun­try people began to trap ants in artificial nests baited with fat. “Fruit-growing families buy these ants from vendors who make a business of collecting and selling such creatures,” wrote Chuang Chi-Yu in 1130. “They trap them by fill­ing hogs’ or sheep’s bladders with fat and placing them with the cavities open next to the ants’ nests. They wait until the ants have migrated into the bladders and take them away. This is known as ‘rearing orange ants’.” Farmers attached k the bladders to their trees, and in time the ants spread to other trees and built new nests.

By the 17th century, growers were building bamboo walkways between their trees to speed the colonisation of their orchards. The ants ran along these narrow bridges from one tree to another and established nests “by the hundreds of thousands”.

Did it work? The orange growers clearly thought so. One authority, Chhii Ta-Chun, writing in 1700, stressed how important it was to keep the fruit trees free of insect pests, especially caterpillars. “It is essential to eliminate them so that the trees are not injured. But hand labour is not nearly as efficient as ant power…”

Swingle was just as impressed. Yet despite his reports, many Western biologists t were sceptical. In the West, the idea of using one insect to destroy another was new and highly controversial. The first breakthrough had come in 1888, when the infant orange industry in California had been saved from extinction by the Australian vedalia beetle. This beetle was the only thing that had made any in- T roads into the explosion of cottony cushion scale that was threatening to destroy the state’s citrus crops. But, as Swingle now knew, California’s “first” was noth­ing of the sort. The Chinese had been expert in bio-control for many centuries.

The long tradition of ants in the Chinese orchards only began to waver in the 1950s and 1960s with the introduction of powerful organic insecticides. Although most fruit growers switched to chemicals, a few hung onto their ants. Those who abandoned ants in favour of chemicals quickly became disillusioned. As costs soared and pests began to develop resistance to the chem­icals, growers began to revive the old ant patrols in the late 1960s. They had good reason to have faith in their insect workforce.

Research in the early 1960s showed that as long as there were enough ants in the trees, they did an excellent job of dispatching some pests – mainly the larger insects – and had modest success against others. Trees with yellow ants produced almost 20 per cent more healthy leaves than those without. More recent trials have shown that these trees yield just as big a crop as those protected by expensive chemical sprays.

One apparent drawback of using ants – and one of the main reasons for the early scepticism by Western scientists – was that citrus ants do nothing to control mealy bugs, waxy-coated scale insects which can do considerable damage to fruit trees. In fact, the ants protect mealy bugs in exchange for the sweet honey-dew they secrete. The orange growers always denied this was a problem but Western scientists thought they knew better.

Research in the 1980s suggests that the growers were right all along. Where X mealy bugs proliferate under the ants’ protection, they are usually heavily parasitised and this limits the harm they can do.

Orange growers who rely on carnivorous ants rather than poisonous chemicals maintain a better balance of species in their orchards. While the ants deal with the bigger insect pests, other predatory species keep down the numbers of smaller pests such as scale insects and aphids. In the long run, ants do a lot less damage than chemicals – and they’re certainly more effective than excommunication.