Isoflavones in Coffee: Influence of Species, Roast Degree, and Brewing Method

Abstract

This paper reports the isoflavone contents of roasted coffee beans and brews, as influenced by coffee species, roast degree, and brewing procedure. Total isoflavone level is 6-fold higher in robusta coffees than in arabica ones, mainly due to formononetin. During roasting, the content of isoflavones decreases, whereas their extractability increases (especially for formononetin). Total isoflavones in espresso coffee (30 mL) varied from approximately 40 microg (100% arabica) to approximately 285 microg (100% robusta), with long espressos (70 mL) attaining more than double isoflavones of short ones (20 mL). Espressos (30 mL) prepared from commercial blends contained average amounts of 6, 17, and 78 microg of genistein, daidzein, and formononetin, respectively. Comparison of different brewing methods revealed that espresso contained more isoflavones ( approximately 170 microg/30 mL) than a cup of press-pot coffee ( approximately 130 microg/60 mL), less than a mocha coffee ( approximately 360 microg/60 mL), and amounts similar to those of a filtered coffee cup ( approximately 180 microg/120 mL).

Phytoestrogens in foods on the Nordic market

“…During roasting, the content of isoflavones decreases, whereas their extractability increases (especially that for formononetin). The data of Alves et al (2010) partly disagree with the reports of other investigators on very low isoflavone content in brewed coffee. Perhaps the analytical methodology has not been optimal for formononetin?…”

“…Most high-quality coffee is produced from Coffea arabica beans, whereas quite a proportion of the coffee beans in instant coffee frequently are from Coffea robusta, and there are all qualities in between. Total isoflavone level is sixfold higher in robusta than in arabica coffees, mainly because of formononetin (Alves et al, 2010). The range in total isoflavones in espresso coffee (30 mL) was between about 40 μg based on arabica beans coffee and about 285 μg based on robusta beans.…”

“…Only the data on the prepared drinks are shown in Table 3. Ground coffee beans of various brands and of various intensities of roasting contained quite different amounts of total genistein (0.15-5.12 mg/kg dw), total daidzein (7.48-31.2 mg/kg dw), and formononetin (0.72-89.1 mg/kg) (Mazur et al, 1998a;Alves et al, 2010). Instant coffee powder contained 5.94 mg total genistein, 1.53 mg total daidzein, 1.62 mg total glycitein, and 0.04 mg formononetin per kg dw .…”

Analytical methods applied for the characterization and the determination of bioactive compounds in coffee

“…Isoflavones and other phytoestrogens of coffee samples are usually determined with the use of HPLC [47] or gas chromatography-mass spectrometry (GC-MS) [48,49] or using automatic SPE and LC-MS/MS [50]. To free the aglicones of isoflavones from glycosides or glycoside esters and quantify them, acid hydrolysis [47] or enzymatic procedure [51] was applied.…”

“…To free the aglicones of isoflavones from glycosides or glycoside esters and quantify them, acid hydrolysis [47] or enzymatic procedure [51] was applied. Thompson et al [49] analyzed the commercial coffee samples for isoflavones (genistein, daidzein, glycitein, formononetin), lignans (secoisolariciresinol, matairesinol, pinoresinol, lariciresinol) and coumestan (coumestrol) with the use of GC-MS.…”