Authors:A. Mazurek, M. Włodarczyk-Stasiak, and J. Jamroz
The objective of the study was to demonstrate the applicability of differential pulse polarography (DPP) technique of the ascorbic acid (AA) assay for the analysis of food samples with various matrices. The following validation parameters were determined: selectivity, linearity, precision, accuracy, limit of detection, and limit of quantification. The limits of detection and quantification were 0.17 and 0.5 mg ascorbic acid per 100 g food, respectively. The average recovery of added ascorbic acid from all matrices was 96.3–103.6%. The values of the coefficient of variation calculated on the basis of AA contents for food matrices were in the range 2–9.26% and Horrat values were 0.37–1.10. Ascorbic acid values of the samples obtained from the polarographic method were compared with those obtained from high-performance liquid chromatography with diode-array detection (HPLC-DAD) used as the reference method. The analytical parameters determined showed that the polarographic method was equivalent to the chromatographic method. Validation of the polarographic method of ascorbic acid assay indicates that it can be applied for the analysis of ascorbic acid concentration in food products that do not contain isoascorbic acid. This means that the method can be recommended for routine determinations.
Authors:S. Cebulak, A. Karczewska, A. Mazurek, and A. Langier-Kużniarowa
The study presents examples of the application of oxyreactive thermal analysis to the geological prospecting of bitumen deposits. Thermal analysis performed under properly chosen analytical conditions allows determination of characteristic features of organic matter and, at the same time, estimation of the thermal history of rocks. Thermal oxyreactivity curves document whether rocks were heated before or not. The results of the oxyreactive thermal analysis correlate well with the results of routine chemical analyses of organic matter (e.g. the composition of kerogen and bituminous fraction, Rock-Eval analysis and others). Our study clearly demonstrates that the composition of organic matter in facially, lithostratigraphically, and biogenetically identical rocks depends on their thermal history.
Authors:M. Włodarczyk-Stasiak, A. Mazurek, J. Jamroz, U. Pankiewicz, and R. Kowalski
The aim of the study was to analyse the influence of the type of osmotic substance (sucrose, glucose, xylitol, trehalose, and sorbitol) on the physicochemical properties of freeze-dried fruit (pear and pineapple). Controlling the functional properties of freeze-dried fruit after osmotic dehydration with aqueous solutions at water activity of aw=0.90 is presented. Decrease in the water adsorption index (WAI) was recorded for all dehydrated samples. The largest decrease (for pears and pineapples by 25 and 65%, respectively) was observed in osmoactive solutions containing trehalose. Considerable increase in the FAI was recorded in samples of dehydrated pineapple. In osmoactive trehalose solutions that increase hardly reached 46%, whereas in sorbitol and xylitol its value elevated to 39% and 13%, respectively. Regardless of the osmoactive sweetener applied prior to freeze-drying, an increase in specific surface area (SBET) of dried materials was observed. For dehydrated pears, SBET ranged from 96 to 697 m2 g−1, and for pineapple, from 115 to 938 m2 g−1. Osmotic dehydration before lyophilisation of fruit samples weakened rehydration relative to the control. The dehydration carried out with osmoactive sweeteners, that is, sorbitol, xylitol, and trehalose, allows obtaining a product with good functional properties that can be successfully used for supplementation of dietary products, in particular for diabetics.