The mypressi TWIST uses 8gm N2O (nitrous oxide) cartridges to provide the pressure for an extraction. Each cartridge will make approximately 4 double shots or 8 single shots.
While 8gm CO2 (carbon dioxide) cartridges will fit in the TWIST, they may leak quite quickly and even immediately. There is also a significant variation in size between different brands of CO2 cartridges so we don’t support their use. CO2 cartridges also have a varying thickness welded metal plate on the front of the cartridge that must be pierced for the gas to escape.
N2O cartridges have a much thinner stretched sheet of metal plugging the end of the cartridge that is more easily pierced. It is possible that using a CO2 cartridge with a very thick plate could damage the piercer on the TWIST.
Neither gas will change the taste of your espresso.