RE SEARCH Potato starch in bioplastics is popular T he big, white building at the Bornse Weilanden on the Wageningen University campus, which once housed ATO-DLO (Agrotechnical Research Institute - Agricultural Research Service), is now filled with high-tech equipment belonging to Food & Biobased Research. Researchers who are working in that area, are fully focused on utilising agricultural raw materials for industrial applications. Frans Kappen is one of these. Like most of his colleagues, he doesn’t have an agricultural background, but studied chemistry. ‘You don’t need it, though. The many laboratories in the building seldom see a potato, onion or beetroot’, Kappen says. What does enter the premises in great quantities, however, are pallets piled high with bags of bioplastics granulates. The granules contain starch from a variety of vegetable origins, including the potato. The starch originates from manufacturers such as AVEBE. AVEBE is a manufacturer that processes the entire potato and produces various products from food to non-food applications. However, in recent years, the laboratories have also been increasingly using starch granules produced in factories that make potato starch from residues (water) from the potato processing industry. An example is Rodenburg Biopolymers in Oosterhout. This company makes the product Solanyl out of starch residues, which is also available in granulates. A lot of foil sheeting Thanks to the arrival of the 3D printer, the starch application has frequently hit the news recently. And yet, the market volume of potato starch polymers destined for the printer industry is not large. For example, a great deal goes to industries that make foil sheeting for the packaging of food, non-food and refuse; the biodegradable refuse bag is an example. To develop new products, the industries usually first go to Food & Biobased Research in Wageningen. The institute not only has the necessary expertise, but it also has the most high-tech equipment for researching new biopolymers. Kappen shows us a number of advanced research appliances in the building at Bornse Weilanden, which enable the researchers to experiment with various biopolymer composites. He shows extruders, among other things for foil and sheeting, injection moulding machines, thermoformers, presses, moulding and analysing appliances, XT scanners and much more. Lots of work in bioplastics ´The chemist has been active in this world of biopolymers for many years, but interest was never greater than it is now´, Kappen tells us. ´We’ve been developing bioplastics for about twenty years now. At the beginning, it was mainly a small group of industries that started to use natural products. As a result of the high oil prices, interest in the product has increased exponentially, resulting in lots of work. This work includes developing plastics that create the desired end product. Plastic bags for potatoes or vegetables, for example, need a different composition from that of a scale model made by a 3D printer. ‘The big advantage of potato starch is that it’s a relatively-pure polymer. The plastics are also more pure and almost transparent-white’, Frans Kappen shows us in Wageningen University’s test room. Potatoes in potatoes Well-known from the early beginning are the biodegradable bags that are also used for packaging potatoes, so you have potatoes in potatoes, partly at least. These are not entirely out of potato starch, because the moisture would quickly melt the bag. Kappen takes a roll of foil and shows that such a biodegradable bag consists of several layers. The example has three layers, the middle one being the starch layer. The outside layers consist of moisture-proof biopolymers, which is often polylactid acid (PLA), a polymer that looks more like synthetic plastics and is moisture proof. The disadvantage is that decomposition takes longer than that of potato starch. Gluten-free and transparent ‘Compared to maize or wheat starch, the big advantage of potato starch is that it’s a relatively-pure polymer, which means that it contains hardly any proteins. Consequently, the plastics from potato starch are more pure and almost transparent-white. Polymers with a lot of proteins are susceptible to discolouration while those from potato starch are much less susceptible. Another useful property is that potato starch plastics don’t contain any gluten. You may wonder why it matters, but manufacturers of animal products do take that into consideration’, Kappen explains. For example, Kappen has brought a dog tooth brush along, which consists of 100% potato starch. ‘Dogs could be allergic to gluten and that’s why manufacturers don’t use wheat starch. Another chemically-important property of potato starch is the long polymer structure. The longer, the better. That’s what it’s all about, both for the industrial plastics and for the printer cartridges’, Kappen explains. ● Leo Hanse Potato World 2014 • number 3 21 Pagina 20
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