Is aluminum pressure cooker reactive? Will it give "off" flavors?
Provided the surface is bare aluminum, it can create off flavors primarily when cooking acidic foods. To avoid this, many aluminum pans are either coated with stainless steel or anodized for a less reactive outer coating. If your pan is bare aluminum, it should be fine for most cooking applications, but you may not want to use it to cook lower pH foods.

Cooking with Aluminum