Analytical Methods
The samples so prepared were examined for the content of dry mass, vitamin C, and β-carotene. The dry matter of the prepared samples of vegetables was determined
according to PN-90/A-75101/03. The determination principle comprised determining the decrease in mass upon
removal of water from the product during thermal drying
at 105ºC under normal pressure conditions [10].
The content of vitamin C (ascorbic and dehydroascorbic acid) was determined using Tillmans Method, as modified by Pijanowski according to the PN-A-04019:1998
standard [11]. The total content of ascorbic acid was determined by reducing dehydroascorbic acid to ascorbic acid
with sodium sulfide, precipitating the excess of sulfides
using mercury chloride, and determining the total ascorbic
acid by 2,6-dichlorophenoloindophenol titration. The
amount of β-carotene was measured according to the PN-
90/A-75101/12 standard by extracting carotenoid from the
test sample using hexane, carotenoid separation on a chromatographic column, and colorimetric determination of β-
carotene at a wavelength of 450 nm [12].
For each sample the chemical analyses were done in
two or three replicates, the relative error not exceeding
5%. The values presented in the tables were calculated
based on 45 repetitions (15 farms × 3 years) for each vegetable species from farms around the ArcelorMittal
Poland SA steelworks, on 15 repetitions (5 farms × 3
years) for vegetable species from organic farms, and on 15
repetitions (5 farms × 3 years) for vegetable species from
retail stores.