The aim of this work was to study the extraction behavior of the main coffee antioxidants (caffeoylquinic acids, melanoidins and caffeine) and the antioxidant capacity, during brewing time in the most widely consumed coffee brew methods (filter and espresso) in coffee. Antioxidant capacity by colorimetric assays (Folin-Ciocalteau, ABTS and DPPH) and electron spin resonance spectroscopy techniques (Fremy's salt and TEMPO) were analyzed. In espresso coffee, more than 70% of the antioxidants (except dicaffeoylquinic acids, diCQA) of a coffee brew were extracted during the first 8 s. In filter coffee, a U-shape antioxidants extraction profile was observed, starting later (after 75s) in Vietnam coffee than in Guatemala one, probably due to different wettability. Other technological parameters, such as turbulences and a longer contact time between water and ground coffee in filter coffeemaker, increased extraction efficiency, mainly in less polar antioxidant compounds as diCQA. In conclusion, these technological factors should be considered to optimize coffee antioxidants extraction that can be used as ingredients for functional foods.

The main hydrophilic antioxidant compounds (3-, 4-and 5-monocaffeoylquinic and 3,4-, 3,5-and 4,5-dicaffeoylquinic acids, caffeine and browned compounds, including melanoidins) and the antioxidant capacity (Folin-Ciocalteau, ABTS, DPPH, Fremy´s salt and TEMPO) were evaluated in Arabica and Robusta spent coffee obtained from the preparation of coffee brews with the most common coffeemakers (filter, espresso, plunger and mocha). All spent coffee grounds, with the exception of those from mocha coffeemaker, had relevant amounts of total caffeoylquinic acids (6.22-13.24 mg/g of spent coffee), mainly dicaffeoyquinic acids (3.31-5.79 mg/g of spent coffee) which were 4-7 fold higher than in their respective coffee brews. Caffeine was ranged from 3.59 to 8.09 mg/g of spent coffee. The antioxidant capacity of the aqueous spent coffee extracts was 46.0-102.3% (filter), 59.2-85.6% (espresso), and less than 42% (plunger) in comparison to their respective coffee brews. This study allowed us to obtain spent coffee extracts with antioxidant properties that can be used as a good source of hydrophilic bioactive compounds.

Antioxidant capacity of the coffee brews prepared with different coffeemakers (filter, plunger, mocha and espresso) was measured by colorimetric (Total Phenolic compounds and ABTS) and Electro Spin Resonance (ESR) spectroscopy techniques (Fremy's salt and TEMPO). Mocha coffeemaker had the highest yield in coffee antioxidant extraction per g of ground roasted coffee, but espresso coffee was the richest in terms of antioxidant intake (per mL of coffee brew) followed by mocha, plunger and filter. Both Folin-Ciocalteau (Total Phenolic compounds) and ABTS assays reacted with standard solutions of chlorogenic acids (CGA) and melanoidins (MO-Ala and MO-Gly). However, Fremy's salt was mainly scavenged by chlorogenic acids, whereas the stabilized radical TEMPO was effectively scavenged by melanoidins, but not by chlorogenic acids. Thus, electron spin resonance (ESR) spectroscopy allows distinguishing between phenolic and nonphenolic antioxidants.Moreover, the addition of pH-regulator agents to coffee, such as sodium carbonate (75ppm) and bicarbonate (75ppm), to extend its shelf-life, slightly increases the pH, modifying the antioxidant capacity in those coffee brews with the highest capacity (mocha and espresso).

Die aus den Dithiocarbamaten (Ia) erhaltenen Isothiocyanate (II) werden als Thioharnstoffe (III) charakterisiert.