The ABTS and DPPH methods are among the most popular assays of antioxidant activity determination. Attempts to adapt them to different analytes and the search for the highest values of antioxidant activity has resulted in a large variety of assay conditions to be presented in the literature, including the way the measurement is made. This makes it difficult to relate the results to real oxidation systems, and often makes it impossible to compare them. Such a comparison is limited in advance by the use of stable radicals that do not exist in nature and that react differently from those generated in food or in vivo. Therefore, it is important to introduce measures aimed at standardizing the conditions of the activity assay, including reaction time and several reaction environments suitable for testing different groups of compounds. In this study, we used natural antioxidants of various structures: phenolic acids, flavonoids, peptides and corresponding amino acids, ascorbic acid and α-tocopherol, and also synthetic analogues of selected compounds. The curves of dependence of the measured absorbance on the concentration of antioxidants were described, the ranges of linearity were determined, and the value of the error made when reading in various ranges of dependencies was estimated. We also determined and compared the activity values using two popular methods (IC₅₀ and TEAC), taking into account different environments and reaction times. Based on the collected data, recommendations were formulated regarding the reaction conditions adapted to the studies of individual groups of antioxidants, and unified reaction times were proposed. Taking into account the state before reaching the equilibrium of antioxidants reacting in a complex manner, this approach may introduce a simplified reference to the competing reaction that occurs in reality.

The aim of this paper was to study the select physicochemical parameters of 58 honey samples of 4 different botanical origins (buckwheat, linden, rape and acacia) using multivariate methods in order to classify honeys according to the botanical origin. Five standard physicochemical parameters were determined according to the international legislation: water content, electrical conductivity, total ash content, free acidity and pH. The results obtained were mostly in agreement with international regulations. Then, the results obtained were analysed by principal components analysis and cluster analysis. The chemometric analysis of results of determinations of the physicochemical parameters demonstrated such markers as electrical conductivity and ash content (i.e. parameters linked with minerals content) to be the most reliable markers in determining the botanical origin of linden and buckwheat honeys. Unfortunately, they appear insufficient for reliable identification of acacia and rapeseed honeys.

The antioxidant capacity and nutritional value of honey are significantly dependent on the content of phenolic compounds. The aim of this study was to compare the antioxidant properties and color of selected honeys and manuka honeys available in the Polish market. The results showed quantitative differences in phenolic acids, phenolic content and antioxidant activity between the honeys, indicating the influence of floral sources. Dark honeys, including buckwheat honey, showed increased phenolic content and superior antioxidant properties. The study revealed remarkable correlations between phenolic content, antioxidant capacity and color. Buckwheat honey showed higher antioxidant properties compared to manuka honey, which is highly valued in the current market. These results highlight the importance of further research into Polish buckwheat honey and advocate its wider consumption due to its high nutritional value and remarkable bioactive properties. In addition, the study contributes to a deeper understanding of honey diversity and highlights the potential importance of regional honey varieties in promoting health.

Due to the fact that consumers are looking for new, health-promoting products, there is a growing interest in various ingredients with a high biological activity that could enrich conventional foods. As is known, chia seeds are a rich source of various health-promoting compounds. The objective of this study was to determine the content of selected biologically active compounds and their antioxidant properties by means of DPPH^●, ABTS^+●, and the ability to chelate Fe (II) ions in chia seeds and yoghurts with the addition of these seeds and seeds soaked in apple juice. It was found that chia seeds are a rich source of bioactive ingredients with beneficial effects on human health—especially polyphenols. All the extracts showed antioxidant properties against the radicals used. The addition of seeds to yoghurt contributed to the presence of polyphenols, while soaking in apple juice resulted in a higher content of polyphenols in yoghurts. The enriched yoghurt extracts showed antioxidant properties against DPPH radicals and the ability to chelate Fe (II) ions. The addition of seeds soaked in apple juice significantly influenced the antioxidant activity against ABTS radicals. The addition of seeds (plain and soaked) did not cause significant changes in the pH of the yoghurts.

The aim of this research was to establish the effect of mild roasting on coffee beans contamination level by polycyclic aromatic hydrocarbons (PAHs). The materials investigated were green Arabica and Robusta coffee beans imported from different countries, as well as those already roasted. The experiment was carried out in a coffee-roasting plant, with the use of an electric coffee roaster, at the temperature of 125–135 °C for 25–26 min. PAHs analysis was conducted by means of high-performance liquid chromatography with fluorescence and diode array detectors (HPLC-FLD/DAD). Results had been verified by means of gas chromatography with mass spectrometry. Contamination level for 19 PAHs, 15 of which were heavy PAHs included on the list of European Union Scientific Committee in Food, varied from 4.29 to 16.17 µg/kg in roasted coffee beans, whereas in green coffee beans varied from 8.66 to 76.63 µg/kg. The results of statistical analysis showed that the contamination level in roasted coffee beans was significantly lower than that in green beans. The applied parameters of roasting did not lead to the occurrence of conditions in which PAHs, especially heavy ones, would possibly be formed. On the contrary, the roasting process itself had significantly reduced the PAHs content in the final product. The reason for this phenomenon was relatively high volatility of light PAHs.

In this study, we investigated the effect of standard preservation of bean seeds on changes in contents and activity of their selected components: dry matter, ash, different forms of nitrogen, composition of protein fractions; total phenolics and condensed tannins; ability to chelate iron(II) ions; antiradical activity against ABTS^•+ and DPPH^•; and capability for inhibiting autoxidation and enzymatic oxidation of linoleic acid. The conducted technological process caused various changes in contents of nitrogen forms and partial loss of phenolic compounds. The antiradical and antioxidative activity of the extracts decreased significantly, while an increase was observed in their ability to chelate Fe(II). These changes were due to the migration of active compounds to the brine, and to their structural transformations and degradation. Longer storage of the sterilized product caused restoration of part of the antiradical activity of the seeds.