CU LTIVATION AND TECHNOLOGY Ethylene tested as sprout inhibitor in storage potatoes SLOW START PROTOCOL The generator does not start supplying ethylene until the stored potatoes have cooled down and reached the desired storage temperature (point A in the graph). Then there is a slow start protocol in which the level of supplied ethylene is built up slowly over 21 days. This continues until the desired ethylene gas concentration has been reached (point B in the graph). If you were to start with a high concentration of ethylene, the respiration activity of the tubers increases, which could result in weight loss. The receptors in the potato then ‘smell’ the ethylene, as a result of which the potato becomes more active. It is therefore important to supply fresh air daily during the start-up phase, in order to keep the CO2 concentration below 0.25 percent (2,500 ppm), so that the potato comes to rest quickly again. Because CO2 is heavier than air, Garos recommends internal ventilation first. ‘The air and CO2 are then well mixed, after which you can let in a ‘flush’ of fresh air. The slow start protocol in combination with ventilation is very important to keep the potato in a resting state. The ethylene generator from Retrain has been pre-programmed and ensures that the potatoes are continuously and automatically in a safe and effective ethylene gas concentration during the entire storage season. Every 30 minutes, the generator logs the data of the ethylene concentration, temperature, CO2 concentration and humidity in the cell’, says Garos. B A Period after logging in Expiration product temperature Ethylene gas concentration Westmaas around the deep fryer with which the baking test will be conducted. They too are curious about the baking quality of French fries and crisps potatoes after 6 months of sprout inhibition with ethylene. Ethylene as sprout inhibitor Prior to the trial, Retrain director Dirk Garos explains the effect of ethylene in potato storage ‘Ethylene stops the sprout lengthening in the potato, while the cell division continues. It therefore has a sprout-inhibiting effect and blocks the sprout’s lengthwise growth. That’s the big difference with the use of chemicals that block the cell division, but the cell lengthening continues. If you do not apply chemical sprout inhibition properly, the sprout can also grow inwards. With some potato varieties, this inward sprouting is a problem but, with ethylene, inward sprouting is absolutely impossible. For sprouts that may already have developed before the potatoes go into storage, ethylene has a blocking effect on the lengthwise growth of the sprout. The resulting thickening at the ends of the existing sprouts shows the ‘ethylene effect’ whereby the cell division continues. These sprouts are very brittle and immediately break off when the potatoes are taken from storage’, he explains. In the storehouse, the Restrain Generator safely produces pure ethylene gas by converting ethanol (alcohol) with the use of a catalyst. At the meeting, the manufacturer shows a completely new type of generator, which they believe is more user-friendly than the previous four generations. ‘The generator produces a low concentration of ethylene which, due to the dynamic properties of ethylene gas, spreads evenly throughout the entire storage process. This doesn’t require any adjustments to the storage, as long as it’s sufficiently airtight, so the required minimum level of ethylene gas is maintained during storage’, says the director. With the help of the Restrain Sensor, which is 40 Potato World 2019 • number 3 Pagina 39

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