Hi! First post from a long time lurker.
Just got my 4th extract kit, a basic porter, from my LHS last night and found they've substituted the hops called for in the recipe. The recipe says to use 1oz Perle for bittering (60 min) and Tetnang for flavor/aroma with ½oz each for 20min and 2min.
The hops provided with the kit are Spalt Select and Northern Brewer (1oz ea). This chart
suggests that I should use the NB for bittering and the Spalt for flavor/aroma. However, no two charts I've found seem to agree on what can be substituted for what, in fact they don't even agree on the alpha acid percentages of the different varieties.
So my first question is am I correct in using NB for bittering and Spalt for flavor?
My second question is should I adjust the schedule or ammounts?