Coffee machines are emerging on the market which claim to superheat the steam they use in heating and aerating milk via a submerged nozzle for latte/cappuccino type beverages.
So instead of the saturated steam typically used to heat and aerate milk coming from a closed boiler at around 1.2 barg or 124°C, they are heating that same steam to 180°C. It is said to produce drier steam (therefore less dilution of milk with water), and sweeter milk (higher Maillard/caramelisation). It is observed however to take longer to bring milk up to the desired drinking temperature.
I've seen a video indicating that superheated steam has extremely high thermal conductivity, yet I've read elsewhere that superheated steam is a bad conductor of heat, having a thermal transfer coefficient (U) of 341 BTU/m² compared to 3960 BTU/m² for saturated steam.
So I'm confused. There is undoubtedly more energy in superheated steam, but does it take longer to release? What happens at the steam/milk interface?