Did you use a lid?

With the small stoves you really need whatever you are using as a pan to have a lid, to help keep in the heat. A typical PSK tin is wide and shallow, which gives proportionately more area from which to lose the heat so it needs a lid even more.

(But don't cook with an air-tight lid because it will go bang.)

A windshield helps, too, as you are aware. Even without, you probably got it hot enough to kill the germs.