Old Hops Woody Flavor

I am trying to determine what is causing a slight wood like bite on my last three batches. I've determined my last three batches all have Northern Brewer Hops in common about .75-1 OZ boiling in 5 gallon batches. I started my hobby in March and have done 20 batches. I bought all of my hops in bulk back in April and stored them in containers in the garage. The garage was quite warm in July and these brews were made in August. I've since learned it is best to store in the freezer and have moved my hops their.

I've heard a lot of people say this is oxedation. The problem is that the flavor is very prominent at 2 weeks, but at 4 weeks in the bottle, it is gone and the beers turn into very good beers. My process has not changed as far as bottling/racking so I doubt the oxedation. I have 3 more pounds of new hops in the freezer so I am not afraid to throw out the older stuff that probably hit 100F in the Garage.

Any thoughts?

Keeping hops in the heat should make their oils evaporate faster, reducing their effectiveness, but I dunno about a woody flavor. Are you possibly getting older extract? Just thinking out loud.

If you can taste it at 2 weeks and not at 4 in the bottle, your beer is probably just too green. The more time you give your beer, the more flavors are going to meld/mellow/intensify and the better your beer is going to taste. I thinks it's general consensus around here that beers should have at minimum 3 weeks in the bottle, more if at all possible. A LOT more if you can manage it.

I wouldn't use hops stored a room temp for several months ... let alone ones stored at 100F. Heat is a catalyst and accelerates oxidation of the hops.

The good thing is that the beers turn out good eventually, but I think I am definately done with the old hops. I've been buying 1 lb bags and keep them in the freezer. Do you think I need to re-seal the bag with one of those air tight bag things? Or is it OK to use a freezer bag and put them back in the freezer after getting what I need on brew day?

Thanks for all the tips.