Don’t ask what it costs, but ask what it brings in CULTIVATION AND TECHNOLOGY ust across the Dutch-German border by the province of Limburg, lies the rural village of Tits. It is here that Demota grows 120 hectares of table potatoes annually. Generally speaking, the harvest is only delivered after 9 months of storage. Lothar Moll, who founded Demota together with Heinz Joseph Derichs and Richard Tambour, tells us that the company takes the greatest care of its product. ´Quality is what we are about´, Moll strongly emphasises. Don’t ask what it costs, but ask what it brings in. That’s the rule we stick to, both in cultivation and in storage. In addition to good equipment, knowledge is the basis for a perfect end product. Suppliers with knowledge and experience such as Piet Huiberts of Agratechniek are what we need in order to work under the most perfect storage conditions´, Moll emphasises. J Ideal ventilation system for table potatoes In 2011, Demota invested in a modern box storage for its table potatoes with space aeration and mechanical cooling. In addition to three units with 1,300 tons of potatoes each, a number of units were also fitted out with a pressure wall for the storage of onions. Today, oneand-a-half seasons later, Moll can tell from experience that space aeration is an ideal ventilation system for table potatoes, because you no longer depend on the outside air situation. After the harvest, the field crop is immediately packed in boxes and put into storage. Depending on the weather conditions, Demota dries and cools the lot with outside air. ‘This year the air was mostly too dry, so that drying with outside air would have resulted in too much weight loss. And that’s why we went immediately for mechanical cooling. The initial cooling process can only be successful with mechanical cooling’, Moll knows from experience. Huiberts adds that Demota stores its potatoes at 4.5 degrees Celsius and 99 percent relative humidity (RH). ‘There’s hardly any weight loss under these conditions. What if the outside air has 61.4 percent RH at 9.8 degrees Celsius. Each cubic metre then has 4.6 grams of water instead of 4.9 grams after inside cooling. When you bring outside air into the cooling under these conditions, you’re drying the potatoes out. Our storage computer always measures absolute humidity. This means that, when we’re storing table potatoes in a unit with mechanical cooling, we only start cooling with outside air when it contains more water per cubic metre than inside the unit. But ´Quality is what we are all about´, Lothar Moll strongly emphasises. Demota wants to avoid every risk of weight loss and cools only mechanically during the storage season. During that season, the shutters are only for five percent open and for only five minutes a day to regulate the CO2 content’, Huiberts explains. ‘Because we’ve installed 22 temperature sensors and an RH sensor in each unit, the ABC computer can create an ideal storage climate with a minimum of air. Frequency-regulated fans From above, standing on the boxes, you ‘The storage process can be controlled from both the storehouse and the computer’, Piet Huiberts shows us in the Demota storehouse. BIG HEAT EXCHANGER Demota has opted for a heat exchanger with a big contact surface. We can either go for working with a small surface and a big difference in temperature or a big surface and a small difference in temperature. A bigger temperature difference results in more weight loss in the potatoes, and subsequently loss of quality in your table potatoes. That’s why Demota opts for working with small temperature differences. Combined with speed-regulated fans, you have the perfect storage climate for table potatoes, according to Moll. ‘An additional advantage, when storing 1,300 tons of potatoes, is that the air circulation only requires 2kWatt per hour’, Huiberts emphasises. Potato World 2014 • number 2 41 Pagina 46
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