Improved competitiveness of Norwegian potatoes

The aim of this project was improved competitiveness and increased value of Norwegian potatoes, as an answer to trends like reduced consumption, increased import and weak economy for the growers. The project has increased the knowledge about the effects of seed potatoes, soil-, climatic-, cultivar-, growing- and storage conditions on yield, tuber size, maturity and skin finish (skin blemish diseases, skin set and bloom/shine). In addition we have studied health effects of potatoes and efficient methods for measuring dry matter content in potatoes. We have completed four years of experiments looking at the effects of soil and climate on skin finish. Potatoes of the cultivars Asterix and Mandel from the same origin were grown in a total of 98 small plots and collected for evaluation. The differences in skin finish were generally greater within each soil category (clay, sand and loam) than between them, but in average potatoes grown on loamy soils had the best skin finish. Trials with cultivars grown on three soils in two years demonstrated major visual differences among cultivars that were partly influenced by the location. The effects of planting and harvesting strategy were also studied in three years of field trials. The effects varied among years, but normal planting date generally gave the best result. A shorter growing period could improve skin smoothness but also reduced skin set and yield. Heating of the seed prior to planting resulted in more silver scurf, delayed planting in less. Experiments with storage strategies the first two months from harvest demonstrated in four years confirmed a positive effect of quick drying on skin finish. The health and physiological quality of the seed potato is very important for the resulting quality. Addition of extra calcium in seed potatoes was found to affect the quality of potatoes the next year, but only with very high levels of calcium. Effects on growth vigour, plant health and maturity of different temperature- and light treatments was studied in four cultivars. It is concluded that 12 h light duration per day is sufficient during traditional pre-sprouting in the spring. This could reduce energy consumption and the risk of high temperatures. A combination of light exposure and higher temperatures under long-term storage increased the physiological age of seed tubers and sprouts considerably. The result is a shorter growth cycle, suitable for short seasons but with reduced yields in longer seasons. No differences in skin finish were found on the ware-potatoes, while a reduction of black scurf on the seed tubers was found after long-term light exposure. The influence on sprout growth of different LED-light qualities during pre-sprouting has been investigated, revealing strongest inhibition of elongation in red and far-red light. Trials with alternative chemical and biological treatments against diseases in seed potatoes, shows silver scurf and skin spot to be the major problems. Several of the treatments have good effect both at harvest, sorting and planting. Treatments with good effect against black scurf resulted in more stems per plant and fewer attacked stems in the yield. The treatments did not result in quality differences in the final yield. This project has also developed calibration models for off-line and on-line near-infrared (NIR) spectroscopic measurements of dry matter contents in potatoes, in collaboration with the FFL project no 199421. Both methods can now be used for estimation of dry matter in whole unpeeled potatoes. The on-line method (moving potatoes) is at least as accurate as the off-line method (not moving potatoes), which might be related to collection of several spectra of the moving potato. The focus towards the end of the project was robustness of the method towards variation of variety, size and measurement speed. The internal dry matter gradients within single potato tubers was also investigated by near-infrared spectroscopy. A good estimation of the gradient indicates that the method is very sensitive to small changes in the dry matter contents of potatoes. The glycaemic effect of cooked potatoes has been studied in the context of a meal. Initial work with in vitro models showed that broccoli fibre reduced the rate of diffusion of glucose from digested potato starch. In a follow up clinical experiment we found that co-consumption of broccoli with potato significantly reduced the maximum level of glucose in the blood and the insulin production in the first 30 minutes, compared to potato eaten alone. Later on, a larger clinical study found that when potato were eaten as a meal together with cooked salmon, herb dressing and carrot, the blood sugar rise was markedly lower and the insulin level higher for the meal than for potatoes alone. These results show, especially for potato which is seldom eaten alone, that clinical studies on glycemic health ought to focus on meals and not just individual foods.

Norwegian potato production faces major challenges. These include decreasing consumption, increased import of ware potatoes, yield depressions and quality problems due to unfavorable climatic conditions. The current project aims to increase the value and quality of Norwegian potatoes and to improve competitiveness against import and alternative products. The competence created in this project will serve as a basis for production of new products of desired qualities. Emphasis will be made to control size d istributions, to improve and maintain a good skin finish (bloom/shine) and to reduce skin blemish diseases. An urgent re-evaluation of the glycaemic health properties of cooked potatoes will also be made. These are currently limiting sale, due to a misco nceived negative impact without taking into account co-consumption of other typical meal components. The project will also result in improved methods for determination and control of external and internal quality parameters.