We test the newest varieties as to their agronomic and processing qualities for the manufacture of crisps and chips. Variety-specific resistance to potato late blight, viral diseases and various scab and tuber defects are of special importance for farmers. Together with the branch, we publish a Swiss Variety List of the Recommended Potatoes annually which describes the most widely grown varieties.
As part of the certification of the plant material, we collect information on the regional and seasonal occurrence of various aphid species that play a major role in transmitting viral diseases. This information is made available on an ongoing basis to seed-propagation organisations by means of bulletins. In addition, we are responsible for the training of the field-inspection experts and seed-stock inspectors.
Disease-resistant, high-quality varieties and healthy seed-stock that is as free of viruses as possible form the basis for environmentally friendly and cost-efficient potato cultivation.
Knowledge of cultivation techniques and of suitability for storage and processing allow for optimal production and utilisation.
Agroscope focuses on regional and current issues and develops recommendations for potato production.
Today, almost 50% of fresh potatoes are used to manufacture various processed products such as crisps, chips, Rösti (hash browns) and other dishes. Raw materials of consistently high quality ensure the quality of the finished product. The most important traits for potatoes destined for processing are a good tuber shape for the product in question, low sensitivity to shock, no internal defaults such as hollow cores and rust spots, low reducing-sugar content, and good suitability for storage of the tubers. Very low reducing-sugar content is the prerequisite for a light colour after frying.
Tuber material from a number of variety tests is processed on several frying dates from August to May. Since both the origin of the tubers and the storage conditions for all varieties at a given trial site are identical (storage temperature of 8°C, or 6°C and 4°C with reconditioning), the reducing-sugar content can be indirectly estimated on the basis of the colour of the fried crisps.
Ten to twelve tubers per variety are peeled and sliced into 1.2mm-thick discs. The sliced potatoes are rinsed twice in lukewarm water to rid them of excess starch. Any water clinging to the potatoes is shaken off before deep-frying. The crisps are then fried for 3 minutes at 170°C in a small deep-fryer in HOLL (high-oleic, low-linolenic) rapeseed oil, stirring constantly. The colour of the fried crisps is assessed visually, according to the Wageningen Colour Reference Card (IBVL colour card for evaluating crispness).
Selection criteria are tubers with a long oval shape, a starch content ranging from 14–17%, and a minimum frying colour of level 5 for the chips. A potato chipper is used to cut the peeled tubers into 8mm x 8mm fries. They are then blanched at 150 °C for 4 minutes. Then they are either refrigerated for a day at 4 °C or deep-frozen at -20 °C for several weeks. Finally, they are fried off at 170 °C for 3 minutes. The sample is then checked visually for frying colour, inner and outer condition, and texture. Taste criteria evaluated are the crispness (toughness, stodginess) and oiliness of the fries.
