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Starch processing and the role of starch potatoes in animal feed

August 16, 2021

Potato largely is eaten by man, but in the past it was widely used as animal feed, especially after cooking, for example by pigs, in Europe. Like humans, pigs can only unlock the starch and digests it after cooking. Ruminants, however, can digest raw potatoes.

Growing potato specifically for animal feed is not practiced anymore, but waste products of the processing industry are still fed to animals. Such waste products may be derived from two different processing types: processing potato for the production of potato starch for food and nonfood applications and processing potato into chips, crisps and other specialties.

Energy-consuming process

The potato starch industry derives starch from starch potato varieties that have a higher than average starch content. In the factory the tubers are washed, ground to mush in the process of which the starch grains freed from the cells and amyloplasts and are ready to be separated from the non-starch components. Therefore, the mush is separated into three flows: starch, juice and fiber. Potato juice contains much protein that is separated from the juice by heating whereby it coagulates and is marketed as potato protein. As the potato juice has to be heated, the energy-consuming process is costly but is needed because of environmental regulations that prohibit dumping in surface water of untreated protein containing potato fruit water. After protein extraction, the remainder of the juice only contains potato fibrous material such as ground skin, cell walls and some remaining starch. It is dehydrated down a dry matter concentration of 16.5% and the product is marketed as pressed potato fiber. The product’s dry matter contains still ample protein, fiber and starch. Due to lactic acid fermentation, the pH of the product decreases to below 4 and for long-term storage, the product can be ensilaged. If desired, it is combined with maize silage where the potato component serves as a cover layer. Potato fiber is used as feed for lactating cows to supplement a protein rich diet when they are fed on grass mainly. Potato fiber after drying can be mixed with coagulated protein as a balanced mash for animals.

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Many animal feed products are made from potato and its waste flows. Raw, uncooked potatoes can only be consumed and digested by ruminants. Non-ruminants can only digest cooked (steamed, fried) potato products. These products are rejects of the processing industry from defects and material released when starting up production lines. Non-ruminants such as pigs, contrary to ruminants such as cows need potato starch to be cooked to unlock the granules for digestion.



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