Jerzy Jamroz

Precision of dehydroascorbic acid quantitation with the use of the subtraction method--validation of HPLC-DAD method for determination of total vitamin C in food.

In food analysis, a method for determination of vitamin C should enable measuring of total content of ascorbic acid (AA) and dehydroascorbic acid (DHAA) because both chemical forms exhibit biological activity. The aim of the work was to confirm applicability of HPLC-DAD method for analysis of total content of vitamin C (TC) and ascorbic acid in various types of food by determination of validation parameters such as: selectivity, precision, accuracy, linearity and limits of detection and quantitation. The results showed that the method applied for determination of TC and AA was selective, linear and precise. Precision of DHAA determination by the subtraction method was also evaluated. It was revealed that the results of DHAA determination obtained by the subtraction method were not precise which resulted directly from the assumption of this method and the principles of uncertainty propagation. The proposed chromatographic method should be recommended for routine determinations of total vitamin C in various food.

Effect of pulse electric fields (PEF) on accumulation of magnesium and zinc ions in Saccharomyces cerevisiae cells

Cultures of Saccharomyces cerevisiae were treated with PEF to improve simultaneous accumulation of magnesium and zinc ions in the biomass. The results showed that the ions concentration in the medium and their mutual interactions affect accumulation in cells. Increasing the concentration of one ion in the medium reduced the accumulation of the second one, in the control as well as in the cells treated with PEF. Under optimized conditions, that is, on 15 min exposure of the 20 h grown culture to PEF of 5.0 kV/cm and 20 μs pulse width, accumulation of magnesium and zinc in yeast biomass reached maximum levels of 2.85 and 11.41 mg/gd.m., respectively, To summarize, optimization of ion pair concentration and PEF parameters caused a 1.5 or 2-fold increase of magnesium and zinc accumulation, respectively, in S. cerevisiae.

Accumulation of selenium and catalase activity changes in the cells ofSaccharomyces cerevisiae on pulsed electric field (PEF) treatment

The aim of this work is the evaluation of selenium accumulation and catalase activity in pulsed electric field (PEF) treatedSaccharomyces cerevisiae cells. Cultures ofS. cerevisiae in the medium containing selenium as sodium selenite were treated with PEF. Applied range of field parameters (field frequency of 1 Hz, intensity of 1.5 kV/cm and pulse duration of 1 ms) does not influence the changes of catalase activity which depend only on the concentration of selenium accumulated in the yeast cells. It was noted for the non-PEF-treated cultures that the accumulation of selenium in the yeast cells increased to 60 μg/g dry mass (DM) together with the increase of selenium concentration in medium from 1 to 3 μg/mL. Consequently, the activity of extra- and intra-cellular catalase also increased. At higher selenium concentrations in medium (4–6 ug/mL) its accumulation in the cells reached 127 μg/g DM which resulted in the decrease of catalase activity. In the PEF-treated cultures, twofold higher accumulation of selenium in the cells was obtained in the whole rang e of concentrations applied, which caused the significant decrease of catalase activity.

Bioaccumulation of the Selected Metal Ions in Saccharomyces cerevisiae Cells Under Treatment of the Culture with Pulsed Electric Field (PEF)

The obtained results demonstrated an influence of PEF on increase in accumulation of various ions in S. cerevisiae cells. Optimization of particular PEF parameters and ions concentrations in the medium caused twofold increase in accumulation of magnesium and zinc ions and 3.5-fold higher accumulation of calcium ions in the cells. In the case of ion couple, accumulation of magnesium and zinc was, respectively, 1.5-fold and twofold higher in comparison to the control cultures. Yeast cells biomass enriched with Mg2+, Zn2+, Ca2+ as well as Mg2+ and Zn2+ (simultaneously) may be an alternative for pharmacological supplementation applied in deficiency of these cations.