Different fats dissolve at rates that are temperature-dependent (which is why cold brew has a different flavor to espresso - a different subset of the oils in t

Different fats dissolve at rates that are temperature-dependent (which is why cold brew has a different flavor to espresso - a different subset of the oils in the bean have dissolved into the water). As a result, each brewing temperature would have a different rate of extraction for each fatty compound. This is why temperature / pressure / flow rate are so important to good espresso - some of the heavier compounds taste very bitter and including much of them in the brew makes for an unpleasant drink.