d considering the concentration of caffeine in the extracts (see
Table 2).As expected,pureCO2 producedextracts withhighcontent
of caffeine (15.9% mass) demonstrating high selectivity to extract
this alkaloid, although recovery was the lowest (21.9%). Among the
cosolvents investigated, ethyl lactate produced the highest caffeine
concentrations, with values similar (14.3% mass in static mode) or
even higher (18.2% mass in dynamic mode) than pure CO2 and the
highest caffeine recoveries as mentioned previously.
Assessment of the co-extraction of substances other than caffeine
is also important since these substances may affect the
sensorial quality and/or bioactivity functions of green tea. In this
respect, the content of catechins was determined by HPLC in the
whole extract of the static assays, and resulted in values of 0.2,
0.8 and 6.7 mg catechins/g tea, respectively, for EA, EL and ETOH
cosolvents. The caffeine/catechins selectivity can be pondered considering
the ratio caffeine/catechins extracted per g of green tea
leaves, which resulted 33 for EA, 16.3 for EL and 1.6 for ETOH. The
cosolvent polarity is influencing the co-extraction of catechins and
thus the caffeine/catechins selectivity