Table 2.
Caffeine content (g/L) in 100% Robusta coffee brews.
| Caffeine Content Av. ± SD (g/L) |
Methods | Time (min) | Amount of Coffee (g) | Amount of Water (mL) | Type of Water | Volume of Coffee Brew (mL) | Pressure (bars) | Temperature (°C) | Degree/Conditions of Roasting | Type of Coffee | Country | Methods of Analysis | References (Year) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.293 ± 0.014 | Pouring water | 5 | 3 | 200 | UHQw | Nd | Nd | 100 | Green | FG | India | HPLC | [63] (2019) |
| 0.227 ± 0.010 | G | ||||||||||||
| 0.186 ± 0.008 | G (tea bag) | ||||||||||||
| 0.760 ± 0.060 | Pouring water | 10 | 2 | 100 | Nd | Nd | Nd | 90 | R | G | Nd | SP | [65] (2018) |
| 0.690 ± 0.030 | Coffee percolator | Nd | Cold water and heated to the boil | ||||||||||
| 0.150 ± 0.010 | Coffee machine (portafilter, De’Longhi, EC145, Italy) | Nd | Nd | ||||||||||
| 0.892 ± 0.079 | Coffee percolator | 15 | 4 | 100 | Dw | Nd | 100 | 100 | R | FG | Indonesia, Yemen, India, and Vietnam | SP | [66] (2017) |
| 0.602 ± 0.069 | Pouring water | Nd | Nd | FG | |||||||||
| 2.581 | Pouring water | 2 | 1 g (calculation for 5 g) | 100 | Dw | Nd | Nd | Hot water | R | G | Nd | SP | [69] (2014) |
| 1.920 ± 0.141 | Pouring water (25 °C), bringing to a boil and filtering | Nd | 50 | 500 | Nd | Nd | Nd | 25 °C and coming to a boil | M | G | Brazil | HPLC | [71] (2014) |
| 1.763 ± 0.061 | D | ||||||||||||
| 1.713 ± 0.057 | L | ||||||||||||
| 1.655 ± 0.049 | Paper filter | 92–96 | M | ||||||||||
| 1.290 ± 0.225 | L | ||||||||||||
| 1.233 ± 0.278 | D | ||||||||||||
| 2.533 ± 0.020 | Coffee machine (portafilter, Saeco Aroma, Italy) | 3 * 0.13 | 7 | 45 | Nd | 46 | Nd | Nd | Nd | FG | Vietnam | HPLC | [72] (2012) |
| 1.153 ± 0.004 | Filter coffee machine | 6 | 36 | 600 | Nd | 532 | Nd | 90 | Nd | FG |
D—dark roasted coffee, Dw—distilled water, FG—freshly ground coffee, G—ground coffee, HPLC—high-performance liquid chromatography, L—lightly roasted coffee, M—medium roasted coffee, Nd—no data available, R—roasted coffee, SP—spectrophotometric method, UHQw—ultra-pure water, 3 * 0.13—three times for 0.13 min.