Heya! I've read that the longest an espresso shot should be left sitting after it's pour is twenty seconds because leaving it long affects the crema. I always assumed that this only applied to shots you planed to drink straight -- i.e., that it didn't apply to mixed coffee drinks like mochas and cappucinos. However, I have an ex-girlfriend barista who swears up and down that it's important with mixed drinks, too -- that leaving the espresso sitting for too long (more than twenty seconds) before pouring it into the frothed milk would degrade it's flavor (she said it would become more bitter), and thus more or less ruin the mixed drink.
Is that true? I've been taking that advice at face value for about a year now, but I started wondering a few days ago -- if you pour the espresso into a milk mixture, you're completely obliterating the crema anyway, so what's the big deal?
Thanks,
-R