Rafał Wołosiak

The purpose of this study was to analyze the effect of the type of extraction solution (water, different concentrations of ethanol), temperature and time on the polyphenol content and antioxidant properties of red clover extracts and the effect of the addition of selected extracts on the antioxidant properties of enriched blackcurrant beverages. In both the extractions carried out under different conditions and in the enriched beverages, the content of selected polyphenols was determined by HPLC. This study confirmed the significant effect of the alcohol content of the extract, extraction time and temperature on the antioxidant properties of clover extracts. Ethanolic extracts had better antioxidant properties than aqueous extracts. The addition of ethanol extracts had a significant effect on the antioxidant properties of the fortified beverages. Increasing the temperature, time or ethanol content in the extracts mostly resulted in an increase in the total polyphenol content in the obtained extracts. Based on the analysis of the response surface, it was found that for the DPPH radical, the best activity was obtained by extraction for 20 min with a solution of approximately 65% at low temperatures. In the case of the ABTS radical, the best antiradical activity was obtained after extraction for 60 min at 80 °C with a solution of approximately 50% ethanol. It was also found that the use of a solution of approximately 60% ethanol after extraction for 60 min at 80 °C would provide an extract with high antiradical activity against both radicals.

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.

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.