Nitrogen and sugar content variability in tubers of Jerusalem artichoke (Helianthus tuberosus)

Several nutritive values for tubers of 114 Jerusalem artichoke (Helianthus tuberosus) populations were evaluated during 2006. The used material is a part of wild sunflower species collection at the Institute of field and vegetable crops and it is situated in Rimski Sancevi, Novi Sad. The samples were analyzed as fresh tubers on 'Venema' automatic laboratory for alpha amino nitrogen, sodium and potassium content. Total sugar content was determined as the brix value on a refractometer. Total nitrogen was determined by the Kjeldahl method on dried samples. Significant variability was found for all analyzed traits. Total nitrogen varied from 0,695 to 2,179% dry weight (mean 1,23%), alpha amino nitrogen content 0,012 to 0,118% fresh weight (m. 0,07%), potassium 0,231 0,452% fresh weight (m. 0,403%) and sodium 0,0003 - 0,0143% fresh weight (m. 0,007%). Total sugar content varied from 13,69 - 22,94% fresh weight (m. 19,14%). Alpha amino nitrogen is an essential nutrient for animals so that it's presence in tubers of Jerusalem artichoke as food is positive. The protein content is similar to the one in potato and as such satisfactory for nutrition. The K/Na ratio is high which is useful, because an increased content of potassium in food can positively affect the reduction of Na/K ratio and lower systolic blood pressure by a significant amount in adults with mild hypertension. Inulin makes up to 80% of the total sugar content in the tubers of Jerusalem artichoke, and as a dietary fiber and a fructose polymer it positively influences digestion and sugar blood levels. The obtained results suggest that selection of cultivars and populations with inappropriate nutritive values is possible. Further research is needed to estimate the share of genetic in total variability and to determine whether the selection for new cultivars is justified.