Čaj do horka
Teď jsem si zrovna po ránu dal Qi Hong Mao Feng a je mi ještě větší horko, než před ním.
In 1996, Monique Hicks, Peggy Hsieh and Leonard Bell published a peer-reviewed scientific paper recording precise time related extraction of caffeine from tea using a modern detection technique (HPLC). This paper, 'Tea preparation and its influence on methylxanthine concentration,' appeared in Food Research International Vol 29, Nos 3-4, pp. 325-330. (FRI is copyright of the Canadian Institute of Food Science and Technology). Methylxanthines caffeine, theobromine and theophyllin all occur in tea and have similar physiological action, but in tea caffeine is the prominent methylxanthine.
In summary: Hicks et al measured the caffeine (plus theobromine) content of six different teas (three bagged and three loose-leaf, including black, oolong and green types). They measured caffeine-extraction in boiling water when steeped for 5 minutes, 10 minutes and 15 minutes. They replicated all their extractions three times to eliminate experimental error. Extrapolation of their data gives the following caffeine-extraction percentages below 5 minutes (averaged over all tea types and formats); note that while loose tea extracted marginally more slowly than tea-bag tea, it made only a couple of percentage-points' difference:
30 seconds: 9% caffeine removal
1 minute: 18% caffeine removal
2 minutes: 34% caffeine removal
3 minutes: 48% caffeine removal
4 minutes: 60% caffeine removal
5 minutes: 69% caffeine removal
10 minutes: 92% caffeine removal
15 minutes: 100% caffeine removal
plati, pre cisti kofein vo vode
2.17 g/100 mL (25 °C)
18.0 g/100 mL (80 °C)
67.0 g/100 mL (100 °C)
skusime cajovy liker?
ethanol 15 g/L
Uživatelé procházející toto fórum: Žádní registrovaní uživatelé a 0 návštevníků