Why would one want to change the temperature?

Coffee is nearly all water. That said, the water you use to extract your coffee impacts the flavor of the coffee. Temperatures below 195 ºF (90.5 ºC) will produce a weakly flavored, or under-extracted, shot of espresso. The higher the temperature, the more “total dissolvable solids” will be present in your final shot leading to a more developed shot of espresso. Of course, you can go crazy and have your temperature too hot. Your Breville Infuser’s PID limits you to 204 ºF (95.56 ºC) F so you can’t get too wild.

Water Quality

I feel like I’d be doing a disservice if I talked about the heat of the water without talking about something that is often overlooked when making coffee at home. The quality of the water you use. Coffee is 98%* water. Have you tasted the water you’re using to pull your espresso? Has it been sitting there for days? You likely are pulling espresso shots with water you wouldn’t drink yourself. Poor coffee beans. Try some filtered water and taste the beauty that is a great shot of espresso. …and keep your water filters in your Breville Infuser up to date!

More

A great blog post about temperature and espresso

A great book on making coffee

Make your own coffee on my favorite machine