The gas works well at preserving the coffee from oxidation. The bigger problem is with water temperature - espresso is incredibly sensitive and will become eith

The gas works well at preserving the coffee from oxidation. The bigger problem is with water temperature - espresso is incredibly sensitive and will become either sour or bitter if the temperature goes outside a very narrow band. This is what you are spending money on with expensive espresso machines - PID temperature controls and lots of heavy brass parts to maintain an even heat. Nespresso machines are pretty cheap and plastic and I believe they use specially made bland coffee blends to disguise this. Frankly you are better off with French press or pourover at home.