Extraction of fructo-oligosaccharide syrups from grated jerusalem artichoke (JA) tubers was studied by water at 20-60&deg / C by determining the yield, degree of polymerization (DP), product profile (DP of up to 6) and prebiotic effect using Lactobacillus plantarum on samples harvested between October and April, stored for 0-20 days. The optimum solvent to solid ratio was 4, the duration of shaking water bath extraction was 40 min and yield based on JA were 12-17%. Temperature was found to improve yield and functionality, and citric acid, at 26 mM, improved the color and darkness by 70 and 80%, respectively. Short-time (1 min) microwaving prior to extraction increased the yield by about 20%, decreased the amount of sugars with DP 1 and 2 and increased the amounts of oligosaccharides (OS) with DP 3-6, although the prebiotic effect increased only slightly / while the color and darkness of the syrup were tripled. Ultrasound-assisted-extraction (USE) gave best performance at 3 min duration / decreased the amounts of sugars with DP 1-2, increased the amounts of OS with DP 3-6, with 18% decrease in the yield. The better functionality of USE syrups were also indicated by 2.5 times higher growth rate of L.plantarum. The application of USE at 60&deg / C compared to 20&deg / C almost tripled the amounts of functional sugars. In order to obtain the largest proportion of monosaccharide units as functional sugars, 10 day storage at 4&deg / C after harvest was indicated. Ultrasonication did not affect the color but the darkness was doubled. The density and viscosity of all the syrups were practically the same.