The use of biostimulants and cultivar selection play an important role in modern potato farming because they influence tuber yield and quality. The nutritional value and processing suitability of potato tubers are affected by their content of total protein, reducing sugars and sucrose. The aim of this study was to determine the effect of biostimulants on the content of total protein, glucose, fructose and sucrose in potato tubers (skin, flesh and whole tubers with skin), at harvest and after 5 months of storage. The experimental materials included tubers of five edible potato cultivars: Irga, Satina, Valfi, Blaue St. Galler and HB Red. During the growing season, potato plants were treated with the following biostimulants: Asahi SL, Bio-Algeen S-90, Kelpak SL and Trifender WP. Control plants were not treated with biostimulants. The total protein content of tubers was determined by the Kjeldahl method. Simple sugars and sucrose were determined by high-performance liquid chromatography. At harvest, total protein concentration was significantly higher in purple- and red-fleshed cultivars than in cream- and yellow-fleshed cultivars. An analysis of tuber parts revealed that flesh had the highest protein content. The total protein content of tubers increased during storage. Biostimulants had no significant effect on total protein concentration in tubers at harvest or after storage. The content of simple sugars and sucrose was higher in the skin, flesh and whole tubers of purple- and red-fleshed cultivars, than in cream- and yellow-fleshed cultivars. Potato tubers with colored flesh accumulated the highest amounts of total sugars. Biostimulants, in particular Bio-Algeen S-90 and Kelpak SL, contributed to the accumulation of monosaccharides and the disaccharide in potato tubers, and, in consequence, total sugars. Their concentrations in potato tubers increased during storage.

The aim of the research presented in this paper was to determine the effect of vessel scale on gas hold- up in gas-liquid systems. The agitated vessel with internal diameters of T = 0:288 m and T = 0:634 m was filled with a liquid up to the height H = T. For the purpose of measurements, two high-speed impellers were used: Rushton turbine impeller (RT) or A 315 impeller.Within the study, the following parameters were altered: superficial gas velocity, impeller speed, impeller type and concentration of aqueous sucrose solution. In addition, influence of the vessel scale on gas hold-up value was analysed. Experimental results were mathematically described. Equations (5)–(7) do not have equivalents in the literature.

The aim of the research presented in this paper was determination of power consumption and gas hold-up in mechanically agitated aerated aqueous low concentration sucrose solutions. Experimental studies were conducted in a vessel of diameter 0.634 m equipped with high-speed impellers (Rushton turbine, Smith turbine or A 315). The following operating parameters were changed: volumetric gas flow rate (expressed by superficial gas velocity), impeller speed, sucrose concentration and type of impeller. Based on the experiments results, impellers with a modified shape of blades, e.g. CD 6 or A 315, could be recommended for such gas-liquid systems. Power consumption was measured using strain gauge method. The results of gas holdup measurements have been approximated by an empirical relationship containing dimensionless numbers (Eq. (2)).