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 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.

Coffee is of interest to consumers and researchers, mainly due to its stimulating properties and positive effects on the human body. Properties of coffee infusions depend on many factors and the most important ones include the roasting process and the brew preparation method. In this paper, we analyzed infusions prepared with the use of pressure methods (professional: espresso and consumer: moka pot brew), obtained from beans roasted to the medium and dark degree, with the aim of determining the share of individual groups of ingredients in the antioxidative properties of coffee. Tested infusions showed various characteristics that were partly related to different parameters of their preparation. In general, a greater amount of phenolic compounds was extracted in moka brews. Espresso, on the other hand, exhibited greater antioxidant activity per portion of the brew and a greater ability to quench free radicals. The degree of roasting had an uneven effect on the antioxidant activity of the brews, depending on the method and its mechanism of antioxidant action. The share of activity of the particular groups of antioxidants in overall activity varied between all methods; the most pronounced changes were observed in the espresso brews. The results indicate, however, that the activity of phenols and melanoidins is based on a mixed mechanism of antioxidant action, but in the case of the latter, the mechanism of hydrogen atom transfer may have an advantage.

During kopi luwak production, coffee fruit is subjected to enzymatic and microbial treatment. While microbial modification of coffee fruit or beans is often investigated, there is little information regarding the influence of the enzymatic part of the process. In this study, green Arabica and Robusta beans were modified using basic animal digestive enzymes (pepsin or trypsin with α-amylase) and various treatment times (3, 6 or 12 h) to determine their effect on bioactive and other quality-affecting compounds. Analyses of coffee composition were performed using spectrophotometric and HPLC methods. Modified and control samples were significantly affected by the treatment. Among enzymes used, only proteases exhibited noticeable impact on target compounds by increasing soluble protein content in green beans. The most advantageous modification time was 3 h. The composition of beans was altered by the roasting step, with the effect not quite corresponding to the previous stage. In conclusion, enzymatic treatment of green coffee beans provides a way to alter coffee composition, which can further influence its quality.

This research aimed to qualitatively analyze the composition of selected extra virgin olive oils from organic and conventional farming available on the Polish market. Determination of the fatty acid profile, determination of the sterol content, and measurement of the acidic and peroxide numbers of the olive oils were performed. Moreover, the content of phenolic acids was determined using the HPLC method, and the antioxidant activity was examined using, e.g., the FRAP and DPPH methods, to establish the differences between the analyzed olive oil samples. The most abundant fatty acids in the olive oil were monounsaturated fatty acids (65.60–78.50%) with oleic acid (59.54–75.36%), saturated fatty acids (14.60–20.49%) with palmitic acid (10.93–16.45%), and polyunsaturated fatty acids (7.80–15.04%) with linoleic acid (6.24–14.34%). The phytosterol fraction consisted of β-sitosterol, campesterol, stigmasterol, clerosterol, ∆5-avenasterol, cycloartenol, 24-methylenecycloartenol, and citrostadienol, and its concentration ranged from 775.23 to 1115.70 mg/kg of the olive oils. The conventional method of olive cultivation influenced campesterol concentration in the extra virgin olive oils, and the concentration was higher in such products than in organic. Tests conducted on the reduction of iron ions (FRAP method) showed that the olive oil obtained from conventional farming (except for one product) had slightly higher antioxidant activity (0.23–0.30 μmol TE/g of olive oil) than that obtained from organic farming (0.19–0.26 μmol TE/g of olive oil). The total content of phenolic acids (oleuropein, hydroxytyrosol, and tyrosol) in the extra virgin olive oils ranged from 133.20 to 226.82 mg/kg.

Coffee quality can be modified with microorganism addition during post-harvest processing. While most studies focus on yeasts and lactic acid bacteria, other species identified in the digestive tract of palm civets might also contribute to the quality of luwak coffee. Bacteria akin to those identified in palm civets’ gastrointestinal tract or feces were evaluated for their potential to modify coffee bean composition. Among those, Bacillus subtilis ATCC 6633, Gluconobacter sp. KKP 3751 and Lactiplantibacillus plantarum ATCC 4080 exhibited strong growth in green coffee extract. The use of these bacteria significantly changed the amounts of basic coffee components (taste and aroma precursors), and slightly altered bioactive compound levels in green and roasted beans. The influence of fermentation duration was evaluated using L. plantarum. A stationary growth phase and positive changes regarding phenolic content were achieved after 24 h of fermentation. Overall, the use of bacteria can influence bean composition, offering the potential to create unique coffee products.